sight and life newsletter - a2zproject.orga2zorg/pdf/30 2002 sl.pdf · sight and life page 108...

SIGHT AND LIFE

INCORPORATING THE XEROPHTHALMIA CLUB BULLETIN

NEWSLETTER 3/2002

Correspondents: Bruno de Benoist, William S. Blaner, George Britton, Omar Dary, TraceyGoodman, Philip Harvey, Rolf D. W. Klemm, Donald S. McLaren, José O. Mora, ChristineNorthrop-Clewes, Vinodini Reddy, Delia Rodriguez-Amaya, Ram Kumar Shrestha, NoelW. Solomons, Florentino S. Solon, Alfred Sommer, Andrew Tomkins, Frits van der Haar,G. Venkataswamy, Emorn Wasantwisut, Clive E. West, Keith P. West Jr. Editor: Martin Frigg

Many ways, one goalSPECIAL ISSUE

SIGHT AND LIFE NEWSLETTER 3/20022

Editorial Contents• Vitmin A and its relatives:

marvellous molecules in keylife processes Page 3

• Vitamin A and the visualcycle: An increasingly com-plex story Page 19

• Effects of processing andstorage on food carotenoids

5• Using immunisation contacts

to deliver vitamin A Page 37• Enriching breast milk with

vitamin A Page 41• Vitamin A, growth faltering in

infancy and gut integrityPage 45

• What makes a successfulsupplement distributor?

Page 51• Vitamin A program in India –

why the controversy?Page 55

• A combined approach tovitamin A deficiency inThailand Page 63

• Progress and challenges incontrolling vitamin A defi-ciency in the Philippines

Page 69• Successful vitamin A supple-

mentation in NicaraguaPage 75

• Vitamin A deficiency in Micro-nesia Page 81

• The contribution of the “caro-tenoid world” Page 83

• Carotenes as dietary precur-sors of vitamin A: their pastand their future Page 87

• A Digest of Recent LiteraturePage 99

• The Task ForceSIGHT AND LIFE Page 108

“Special issue”

We take great pleasure in pub-lishing this special issue of theSIGHT AND LIFE Newsletter,which is devoted entirely to arti-cles by our correspondents. Wewanted to give our correspond-ents an opportunity to publishtheir thoughts and findings with-out any limitations on topic, fo-cus or space. Also, this issue wasconceived as a way of thankingthem for the dedicated supportwhich has helped make theNewsletter ‘required reading’ onthe subject of vitamin A defi-ciency. We were pleasantly sur-prised at how many of our corre-spondents answered the call forcontributions. Their overwhelm-ing response is the reason whythis issue is about twice as thickas usual. Your postman maycomplain about the extra weight,but we feel the quality of the con-tents justifies every gram!

As always, this special issuebrings together contributions re-flecting the different back-grounds, disciplines andspecialisations of a diverse groupof authors. Our newsletter hasalways promoted a multi-discipli-nary approach, and this special

Correspondents’ Issue is no ex-ception.

Public health issues have to bedealt with on an internationalscale and require the involve-ment of specialists working inevery field that can contributeuseful scientific insights or ap-plied know-how. Accordingly, ournewsletter aims to reach a verybroad and diversified readership.Our growing circulation indicatesthat we are succeeding — thisyear it is up to 10,000 printedcopies per issue, as comparedwith roughly 9000 copies a yearago.

The SIGHT AND LIFE offices inBasel are run by a small staff andwith a relatively limited infrastruc-ture. For that reason the reportsand advice supplied by our cor-respondents are vital. These col-leagues — every one of them arespected expert in his field —are our eyes and ears in coun-tries around the globe. With thehelp of the Newsletter, informa-tion can be shared much morequickly and thus deployed moreeffectively in the fight against vi-tamin A deficiency.

Finally, on a personal note, Iwould like to add that, for my col-leagues and myself in Basel,working with our correspondentsis an enriching experience andone that we would hate to dowithout.

NEWSLETTER 3/2002 3 SIGHT AND LIFE

1. IntroductionThe discovery of vitamin A, notfar short of 100 years ago, ush-ered in a new era in biochemis-try and medicine, the vitamin era.In evolutionary terms, however,vitamin A – in a slightly differentform – was early on the scene inone of the most ancient bacteria.It was helping to obtain energyfrom light when the environmentlacked oxygen. Probably quite afew million years earlier colouredprecursors of vitamin A, carot-enoids, were helping bacteria totrap light for photosynthesis – thevery foundation of the extrava-gant diversity of life that was tocome.

Photosynthesis goes on insidechloroplasts, which share withmitochondria an amazing chap-ter in evolutionary history. It isbest not to go into this now butleave it for those unfamiliar withit to enjoy later.

In other ways carotenoids con-tinue to surprise us with the use-ful things they find to do!

Primitive nervous systems devel-oped for the transduction, orpassing on, of various kinds ofstimuli from the environment.Probably the most useful andcertainly the most studied form isphototransduction in the aston-ishing variety of eyes. Here also

relatives of vitamin A are indis-pensable to trap photons.

As the end of the 20th centuryapproached, other vitamins werediscovered and vitamin A was justone vitamin among many others.It was something the bodyneeded but could not make on itsown and therefore had to getfrom the diet.

Some of the close relatives of vi-tamin A are now openly classedas hormones involved in cellsthroughout the body with nuclearreceptors and gene transcription.Even here light may be playing apart.

Within the space of a short arti-cle like this it will be possible onlyto scratch the surface of these

Vitmin A and its relatives:marvellous molecules in key life processesProf. Donald S. McLaren, 12 Offington Avenue, Worthing, West Sussex BN14 9 PE, UK

CH2OH

CHO

COOH

CHO

CHO

A

B

C

D

F

E

Figure 1. A Vitamin A (retinol); B all-trans-β-carotene; C all-trans-retinoicacid; D all-trans-retinal; E 11-cis-retinal; F 3-dehydroretinal.


very complex processes, but if itwhets the reader’s appetite formore then the references citedare designed to satisfy with moredetailed accounts.

Some definitions of the classesof compounds to which vitamin Aand its relatives belong will serveto introduce them. Although vita-min A (Figure 1 A, retinol, all-trans-retinol) is mentioned first itis derived in nature from a hand-ful of carotenoids, most com-monly from β-carotene (Figure1 B, β-carotene, more correctlyβ,β-carotene). Comparison ofFigures 1 A and B shows that twomolecules of retinal might be ob-tained from fission of the centralchain. This is indeed what theenzyme β-carotene-15,15’-dioxy-genase commonly brings about,although eccentric cleavagedoes occur and may result insome interesting products (1).Vitamin A is a generic term todesignate any compound pos-sessing the biological activity ofretinol. Of particular interest here

are all-trans-retinoic acid (Figure1 C), the main form active in DNAtranscription, all-trans-retinal(Figure 1 D) and 11-cis-retinal(Figure 1 E) involved in the visualcycle in most animals, and3-dehydroretinal (retinal 2) (Fig-ure 1 F) in the visual cycle of afew others.

The term retinoids applies to anynaturally occurring form of vita-min A and to many synthetic ana-logues of retinol, with or withoutbiological activity.

More than 600 carotenoids (ex-cluding isomers) are known (2).Some carotenoids have formallylost part of the 40 carbon skel-eton. Apocarotenoids have lostcarbon atoms from the ends ofthe molecule and norcarotenoidsfrom within the chain. Those thatcontain one or more oxygen func-tion are known as xanthophyllsand the parent hydrocarbons arecarotenes. All are polyiso-prenoids (small multiples of iso-prene, C5H8), possess an exten-

sive system of conjugated dou-ble bonds, usually contain 40Catoms, commonly show internalsymmetry and often have one ortwo cyclic structures at the endof their conjugated chains (β-carotene see above, Figure 2 Alycopene, Figure 2 B lutein).

The most striking feature ofcarotenoids is the long system ofalternating double and singlebonds. It gives them their distinc-tive molecular shape, chemicalreactivity, and light-absorbingproperties. Geometrical isomeri-sation occurs and most carot-enoids exist in the more stabletrans-form, rather than the cis-form. Carotenoids as a group arevery hydrophobic, but cis-iso-mers may be more readily solu-bilised, absorbed and trans-ported. The usual indication ofcarotenoid breakdown is bleach-ing; also seen in coloured rela-tives of vitamin A.

For vitamin A activity to occur acarotenoid must include at least

A

B

OC

HO

OH

Figure 2. A Lycopene; B Lutein; C β-ionone.


one unsubstituted β-ionone ringand a polyene sidechain. Theother end of the molecule mayhave a cyclic or an acyclic struc-ture. It may be lengthened but notshortened to less than an 11-car-bon polyene chain. Chain length-ening decreases activity. Withoutcarotenoids life would not only beimpossible but the worlds oftrees, flowers, fruits, birds and

other life forms would lack theirspectacular red, orange, and yel-low colours.

As light plays a central role inmuch of the activity of these mol-ecules, it is important to presentcertain features of its nature (3).Electromagnetic radiation of allkinds is a wave of electric andmagnetic fields propagating at

the speed of light (approximately186,282 miles/sec) throughempty space. A photon is a quan-tum of light, virtually massless,and of what is known as “spin 1”spinning like a twisting screw. Aswill be seen from Figure 3, onlya very small part of the entireelectromagnetic spectrum ismade up of the visible spectrumcomposed of the familiar colours

Wavelength (m)

The electromagnetic spectrum

Frequency (Hz)

10–15

1023

1021

1019

1017

Visible1015

1013

1011

109

107

105

103

10–13

10–11

10–9

3.9 x 10–7 m

(violet)

7.8 x 10–7 m

(red)

10–7

10–3

10–1

10

103

105

10–5

γ-rays

X-rays

Ultraviolet

Infrared

Microwave

Radio

Short wave

Medium wave

Long wave

UHF

VHF

Figure 3. Electromagnetic radiation spans an enormous range of frequencies or wavelengths. Thespectrum is customarily designated by fields, waves and particles in increasing magnitudes of fre-quencies, with the visible spectrum occupying a very small fraction; (adapted from reference 3).


of the rainbow. It spans approxi-mately wavelength 350–800 nm(a nanometre is 1 billionth of ametre). Some animals see ultra-violet light, but this will not be pur-sued further.

Colour of an object can result inseveral different ways. One of themost important of these depends

on the selective absorption oflight by molecules whose size orvibrational wavelengths, or both,lie within the range of the visiblespectrum. Selective absorption ofvisible light results from retarda-tion in the relative speed or vi-brational frequency of the manyrapidly vibrating electron pairsfound in a compound. Sufficient

modification in the frequency ofvibration imparts to the wholemolecule a special motion, orchemical resonance, that ab-sorbs entering light rays ofmatching frequency with the evo-lution of heat. The residual,unabsorbed light is transmitted tothe eye.

The colour reflected by a pigmentincludes all the wavelengths ofvisible light except the absorbedfraction. The observed colour ofa compound depends on thedominant wavelength reflected.Thus a substance absorbingshorter visible light (i.e. violet andblue) will appear yellow or orangeand so on.

2. PhotosynthesisThis fundamental life processtakes place not only in higherplants and trees, but also in vari-ous kinds of single cell organisms(4). These include anoxygenicphotosynthetic bacteria, cyano-bacteria and algaebacteria, aswell as algae and plankton.Phytoplankton are responsiblefor nearly half of all the photosyn-thesis going on in the world andproduce about 50% of the oxy-gen in the atmosphere. Factors,both man-made and natural, thatinterfere with their growth are ofobvious importance for life onearth.

Fossil evidence suggests that thefirst known organisms resembledpresent-day blue-green algae orcyanobacteria and dated fromabout 3.6 billion years ago. Forabout the first 1.6 billion yearsthese were possibly the only formof life. Carotenoids were mostlikely among the pigments assist-ing in photosynthesis at that time.

Chlorophyll a

β-carotene

Chlorophyll b

400

100

80

60

40

20

0

100

80

60

40

20

0

500

Wavelength (nm)

Absorption spectra

Action spectrum of photosynthesis

Ab

so

rptio

nR

ela

tive

ra

te o

f p

ho

tosyn

the

sis

600 700

A

B

Figure 4. Photosynthesis at different wavelengths.(A) The ability of light ofdifferent wavelengths to support photosynthesis; (B) The absorption spec-tra for three photosynthetic pigments; chlorophyll a, chlorophyll b, andβ-carotene; (adapted from reference 4, page 748).


We now have a clear understand-ing of the genetics and molecu-lar biology of the process of bio-synthesis of carotenoids com-mon to all members of the plantkingdom with this capability (5).

The prime movers in photosyn-thesis are the green pigmentschlorophylls a and b, but their rolein trapping light is considerablyenhanced by the additional pres-ence of various carotenoids. Justhow well chlorophylls andcarotenoids work together isshown in the two parts (A) and(B) of Figure 4. There is a strik-ing similarity between the twocurves showing (A) the relativerate of photosynthesis and (B)the amount of light absorption atdifferent wavelengths. In thesegraphs the only carotenoidshown is β-carotene and on thisevidence it appears to contributemore than the chlorophylls. Thusit is not surprising that the con-centrations of carotenoids andchlorophylls in any given sourceare often proportional, and edible

dark green leaves are usuallyamong the rich sources also ofprovitamin A.

The entire process of photosyn-thesis goes on inside an intra-cellular structure called thechloroplast (6) (Figure 5), wherethe carotenoids of plants are al-ways found. The outcome of theprocess is very simple; light en-ergy, trapped by chlorophyll,carotenoids and some other pig-ments, is converted into that ofcarbohydrates.

From carbon dioxide in the at-mosphere and water, in the plantcarbohydrates for food are pro-vided not only for the plant butalso for animal predators, includ-ing man. Oxygen is released intothe atmosphere as a waste prod-uct. The details are very complexand are not part of the presentstory. A few Nobel prizes havebeen earned along the way.

In the present context only a briefaccount of the part played by the

carotenoids is appropriate. Insidethe chloroplast there are twophotosystems (PSI and PSII).The carotenoid and chlorophyllparticles are located on thesephotosystems that are visible asparticles in the thylakoid mem-branes (Figure 5). PSI is light-dependent, but PSII is light-inde-pendent, although the processtakes place in the light!

In the previous section we sawhow light of different wave-lengths, and therefore colours, isabsorbed. When a molecule of aphotosynthetic pigment, like acarotenoid, absorbs light it is saidto become “excited”. The energyfrom photons boosts electrons toa higher energy level. This en-ergy is “trapped” and convertedto chemical energy. It is unstableand the first stage of photosyn-thesis involves movement of ex-cited electrons between mol-ecules within photosystems.Water is split into hydrogen andoxygen, and oxygen is releasedas a waste product. In the sec-

outermembrane

innermembrane

lipid droplet

starch grain

free ribosomes

small (70S)ribosomes

polysome

onegranum

thylakoid

intergranal lamella (one thylakoid)

chloroplast DNA

membrane-boundribosomes

stroma

chloroplastenvelope

Figure 5. The structure of a chloroplast with simplified membrane structure. Adapted from Introduction toPlant Physiology, 1995, Hopkins-W.G.


ond light-independent stage car-bon dioxide is reduced to carbo-hydrates, using the chemical en-ergy in the form of adenosine tri-phosphate (ATP) and hydrogen.

The story of photosynthesis is byno means over. Some of the mostexciting research goes on in thelargest oceans on the smallestorganisms and will affect the fu-ture of life on earth (7).

3. Other functions ofcarotenoids

Less well understood as far astheir mechanisms are concernedand receiving less publicity thantheir role in facilitating photosyn-thesis, other functions of carot-enoids are attracting increasingattention these days.

1) Carotenoids in higher plantsare capable of channelling lightenergy away from chlorophyllin an aerobic atmosphere (8).The xanthophyll cycle (Figure6) appears to be especially in-volved in this process. Most

plants are able to alter theircarotenoid composition inthylakoid membranes (Figure5) in response to growth un-der deep shade versus fullsunlight. The proportion ofcarotenoid/chlorophyll mol-ecules is greater in sun thanshade and the proportion ofxanthophyll cycle carotenoids(violaxanthin, antheraxanthin,and zeaxanthin) versus non-xanthophyll cycle carotenoidsincreases in sun comparedwith shade. It is generallyagreed that the main site ofenergy dissipation is the light-harvesting antennae on thethylakoid membranes.

2) In plants and microorganismscarotenoids may protectagainst the potential formationof singlet oxygen by a tripletenergy transfer mechanism(9). More recently it has beenshown that a singlet energytransfer mechanism, from ex-cited chlorophyll to zeaxanthin,can also prevent oxidative dis-ruption of the photosyntheticprocess (5). Besides caroten-

oids a balanced diet containsother antioxidant substances,such as some essential ele-ments and phytophenols andmany other compounds forwhich no essential nutritionalfunction is known. Many trials,both curative and preventive,in animals and in humans, areunderway in relation to manydiseases, particularly commonchronic conditions such asvarious forms of cancer,atherosclerosis and the degen-erative eye diseases cataractand age-related macular de-generation (10). Of special in-terest in the present context isthe evidence that the twocarotenoids zeaxanthin andlutein are preferentially depos-ited in the retina in man (8).Other carotenoids are absent.Near the centre of the retinathere is a yellow spot, themacula lutea, where these pig-ments are concentrated. In thecentre of the macula is thefovea, where all the photo-receptors are cones and vis-ual acuity is at its greatest(Figure 7). Zeaxanthin tends to

O

HO

OH

O

HO

OH

O

HO

OH

Violaxanthin

Antheraxanthin

Zeaxanthin

De-epoxidationtypically occurs

within minutes

Epoxidationoccurs within

hours, but

can take days

under

additional

stresses

Excess light

Excess light

Low light

Low light

Figure 6.The xanthophyll cycle, responsible in higher plants for dissipation of excess energy absorbed from sun-exposed sites and consequently a high demand for photo-protection; (adapted from reference 8).


predominate centrally andlutein peripherally. This corre-sponds with the distribution ofrods and cones respectively.These findings may have sig-nificance in relation to the com-mon blinding disease age-re-lated macular degeneration.Much more work is neededbefore human dosing withcarotenoids on a wide scalecan be safely recommended.Under some circumstancescarotenoids have been shownto be prooxidant (8).

3) The fall of leaves of deciduoustrees in autumn is broughtabout by a carotenoid deriva-tive, abscisic acid, whichcauses a nipping off of the leafat the junction with the stem, a

process known as abscission.The xanthophyll xanthoxingives rise to abscisic acid,which is a major plant anti-growth hormone (Figure 8)(11). This is brought about bycell membranes being mademore permeable to water, thuspreventing the freezing of cellwater. The extracellular waterin plants freezes first. The re-sulting osmotic dehydration ofcells means that the cell fluidsbecome more concentrated insolutes and their freezing pointdecreases.

4) The attractive red, orange andyellow colours of many autumnleaves are due to their xantho-phyll content. The colours be-come obvious only after the in-

tense green of chlorophyll hasbeen broken down with a fallin temperature in autumn. Anexperiment was carried out byobservation of the behaviour ofthe insects, aphids, known todamage deciduous trees in theautumn. It was shown that au-tumn colouration was strongerin species of trees facing a highdiversity of damaging special-ist aphids. This was interpretedto mean that the bright colourswere a warning to pests thatthe tree would fight any infes-tation. The heavier an infesta-tion was likely to be, the morethe tree would have to gain bysignalling its intentions (12).

4. The chloroplastand eusymbiosis

All known organisms are dividedinto two groups, prokaryotes andeukaryotes. A prokaryote is asimple organism that does notcontain a true nucleus sur-rounded by a nuclear membrane,and division occurs by simple fis-sion. In an eukaryote a cell has atrue nucleus as in all higher or-ganisms. In addition, eukaryoticcells contain a variety of internalorganelles, and among these twoare special, mitochondria andchloroplasts. These are of aboutthe same size as bacteria and,like bacteria, have a circular ge-nome outside the nucleus as wellas the usual nuclear genome withwhich the former collaborates(Figure 5). The resemblance ofmitochondria and chloroplasts tobacteria led to the idea that theymight be free-living bacteria thatwere engulfed by a primitiveeukaryote and flourished insidethis as endsymbionts. This is nowgenerally accepted. Chloroplastsare able to adapt to environmen-

Papilla

(optic disc)

Macula

lutea

Retinal

blood vessels

Figure 7. The macula lutea is an oval yellow spot at the centre of the retina,2 mm from the optic nerve. Central vision occurs when an image is focusseddirectly on the fovea centralis, a small area, 0.5 –1.0 mm in diameter, at thecentre of the macula. At the fovea the inner layers of the retina are pushedaside so that light can impinge directly on the receptors. In primates onlycones are present; (adapted from reference 26, page 697).


tal changes such as a low or highlevel of light. When grown in com-plete darkness they lack chloro-phyll but retain carotenoids. Thusmany chloroplasts are light-regu-lated and carotenoids play anactive part under these circum-stances (13).

Lynn Margolis, the American bi-ologist who has probably contrib-uted more experimental evidenceto support the concept ofendsymbiosis than anyone else,has written, “Eukaryotes evolvedsymbiotically from eating, invad-ing, infecting and cohabiting bac-teria” (14).

5. Rhodopsin andthe simplestknown light-drivenproton pump

The archaebacterium Halo-bacterium halobium under nor-mal conditions in the presence ofabundant oxygen oxidises fuelmolecules to generate ATP, as domost aerobic organisms. How-ever, when oxygen is scarce itsynthesises large amounts of amembrane protein called bac-teriorhodopsin, which takes partin a light-driven proton pump (15).Light isomerises the all-trans-reti-nal chromophore to the 13-cis-form, at the same time pumpinga proton (H+ atom) from the cy-tosol to the outside.

The complex atomic details ofthis proton pump have beenworked out in recent years. At theroot is the photoisomerisation ofretinal that produces a bend inthe molecule of the chromophoreof only 2 Å (Ångström = a hun-dred millionth of a centimetre)(Figure 9). Something very simi-lar is seen in the visual cycle (seesection 6 below).

6. Photo-transduction

This word refers to the processwhereby the energy of photonsis converted in photoreceptorcells into a nerve signal for trans-mission of the message onwardstowards the brain for interpreta-tion. There are many other exam-ples of transduction of stimuli,including hearing, taste, smelland so on, but that of sight hasbeen studied much more thanany other.

The mammalian eye

The retina is composed of tenlayers and the photoreceptorsform the outermost of these un-derneath the retinal pigment epi-thelium (Figure 10). This meansthat before the process ofphototransduction can begin,light has to pass through all othernine layers. This strange ar-rangement applies only to themammalian retina.

There are two types of photore-ceptor; rods for vision in poor lightand cones for vision in bright lightand for distinguishing betweenlight of different colours. Conesand rods have differences in bothstructure and function (Figure11). While the chromophore is thesame in both, namely 11-cis-reti-

HO

O

OH

O

O

OH

CHOHO

O

CHO

CHO

OOH

COOHO

OH

9-cis-violaxanthin

Xanthoxin

O2

Abscisic aldehyde

Abscisic acidC25 epoxy apo-aldehyde

Figure 8. Proposed pathway of abscisic acid biosynthesis in higher plants;(adapted from reference 11).


nal, the proteins attached to it aredifferent. Rhodopsin is a very wellcharacterised G-protein (see be-low) in the rods (Figure 12), andthe cones have one of threeslightly different versions of asimilar protein, iodopsin. Thesethree kinds of cone photorecep-tor are either blue, green, or redlight absorbing.

The importance of G-proteins hasbecome appreciated only in re-cent years. Many receptorslinked to effector systems bytrimeric guanosine triphosphate(GTP)-binding proteins (G-pro-teins) have been described. Thechromophores of mammalian vi-sion, rhodopsin and iodopsin,and bacteriorhodopsin (Figure 9)are only a few among many G-proteins. These proteins regulatethe activity of a specific plasmamembrane enzyme or ion chan-

-A212

A85HA82

NH

Lys

HA96

+

+ -

A212N550

L550

BR568

-

A96-

HN

Lys

HA85

A82

HA96

HA85

A82

A212

A212

M412

M412

-

-

HA96

HA96

-

NH

Lys

HA82

A85

NLys N

Lys

A212-

+

+

A82

HA85

H+

H+

+

Coupled isomerisation

and protein

conformational change

Reprotonation

Photoisomerisation

Proton transfer

Protein conformational change

Cytosolic side

Extracellular side

Figure 9. Proposed mechanism of light-driven proton pumping by bacteriorhodopsin. Adapted from AnnRev Biophys Chem, 1991, page 491, Mathies-RA, Lin-SW, Ames-JB, Pollard-WT.

Figure 10. Schematic diagram of the ten layers of the retina;(adapted from reference 26, page 691).

1. Retinal pigment

epithelium

2. Outer and inner

segments of

photoreceptors

3. External limiting

membrane

4. Outer nuclear layer

5. Outer plexiform layer

6. Inner nuclear layer

(bipolar cells)

7. Inner plexiform layer

8. Ganglion cell layer

9. Retinal (optic)

nerve fibre layer

10. Internal limiting

membrane


nel (in the case of rhodopsin) inresponse to receptor binding.

Several different types of G-pro-teins couple to specific plasma-membrane enzyme-effector sys-tems leading to the generation ofa soluble second messenger.Cyclic adenosine monophos-phate (AMP) was the first discov-ered. In an analogous systemguanylate cyclase produces cy-clic guanosine monophosphate(GMP) that specifically activatesa cyclic GMP-dependent proteinkinase. This is used in the visualsystem.

The photoreceptors of the humanretina are so sensitive that a sin-gle one of them can be triggeredby a single photon. In a rod thisgenerates a current of approxi-mately 1–3 pico-amperes; in acone only about 10 femto-am-peres, or about 1/100 that of arod. However, the response timeof a cone is about four timesfaster than that of a rod. Conesare better suited for discerningrapidly changing events; rods forlow-light visual acuity.

The process of phototrans-duction goes on in the outer seg-ment of the rods and cones andthe signal generated passesdown a fine cilium to the innersegment (Figure 11). Inner seg-ments of both rods and conescontain many mitochondria andribosomes. They generate ATPrapidly and actively synthesiseproteins.

The outer segments of the rodshave received much more atten-

ROD CONE

Nucleus

Golgi complex

Mitochondria

Site of phototransduction

New disc formed here

Phagocytosis of old discs

by pigment epithelial cells

Photopigment embedded

in membrane folds or discs

Melanin

granules

Synapses with bipolar

and horizontal cells

Metabolic machinery for

synthesis of photopigment

and production of ATP

Synaptic Terminal

Outer Segment

Inner Segment

Figure 11. Diagram of a generalised mammalian retinal cone (right)and rod (left); (adapted from reference 26, page 692).

Cytosolic side

Membrane

Carboxyl

terminus

Amino

terminus

Intradiscal side

Vitamin A

binding site

Transducin,

rhodopsin kinase

and arrestin-

binding region

45 Å

Figure 12. Rhodopsin molecule. The dashed circle in the centre of the trans-membrane region indicates the site and plane of 11-cis-retinal to the lysineresiduess at position 206 and 209. Adapted from The Eye: basics sciencesin practice, page 194.


tion than those of the cones,probably because they are muchmore numerous. In the humaneye there are about 100 millionrods to 3 million cones. The outersegment of each rod contains astack of about 1000 discs. In thepresent context the story of thecomplex process of vision will betaken little further than the phaseof phototransduction, in which the

relatives of vitamin A are in-volved.

Before light excitation 11-cis-reti-nal locks the receptor protein(opsin) in its inactive form. Theprimary event in visual excitationis the photoisomerisation of the11-cis-isomer of the Schiff-baseof retinal to the all-trans-form(Figure 13). As can be seen in

Figure 13 the energy in a photonhas been converted into the en-ergy of atomic motion to the ex-tent of 5 Ångström. Much of theisomerisation of retinal takesplace within a few picosecondsgiving rise to a series of interme-diates. One of these, meta-rhodopsin II, called photoexcitedor activated rhodopsin, triggersan enzymatic cascade that acti-

1211

1211

Light

Schiff-base linkage

5 Å

11-cis-isomer All-trans-isomer

1112

1211

Figure 13. The primary event in visual excitation is the isomerisation of the 11-cis-isomer of the Schiff-base of retinal tothe all-trans-form. This markedly alters the geometry of retinal. The Schiff-base linkage of retinal moves approximately5 Å (Ångström) in relation to the ring portion of the chromophore; (adapted from reference 15, page 335).

Arrestin

R-arrestin

Rhodopsin (R)

Activated

rhodopsin (R*)Inactive

phosphodiesterases

Guanylate cyclase

Active

phosphodiesterases

hydrolysis

activates

GTP

GMP cGMPNa+ channel closes

Ca2+ cytosolic Recoverin Na+ channel opens

GDP

hν (photon)

R-P

P

αβγTransducin Transducin

Figure 14. Phototransduction of a single molecule of rhodopsin leads to a series of enzyme activation and regen-eration responses that underly the opening of many channels. Adapted from The Eye: basics sciences in practice,page 194.


vates a G-protein (transducin)cascade leading to cyclic GMPhydrolysis (Figure 14) which inturn closes cation-specific chan-nels to generate a nerve signal.Later, light-induced lowering ofthe calcium level coordinates re-covery and adaptation.

The rhodopsin molecule alters its“colour”, its light-absorbing prop-erties, from magenta, throughorange to yellow and ultimatelyto white or “bleached”. Now it hasbecome opsin and dissociatedall-trans-retinal. The opsin under-goes regeneration by bindinganother molecule of 11-cis-reti-

nal. In addition to restoring light-absorbing capacity this is criticalfor shutting off the pigment’scatalytic activity and thus allow-ing full dark adaptation to occur.The details of how 11-cis-retinalis reformed in the eye from all-trans-retinol have recently beeninvestigated (16). Figure 15 givesdetails of this revised visual cy-cle and a key feature is the dem-onstration of a role of light in 11-cis-retinal formation within theretinal pigment epithelium. Thispathway is an alternative to darkisomerisation, previously known,which yields 11-cis-retinol.

Some variations on themain theme

a) Colour vision in primates

It seems that in the earliest ver-tebrates that arose about 520million years ago there was a sin-gle photopigment in cone-likephotoreceptors. By the time theearliest four-legged animalemerged the single pigment haddiverged into five distinct families,with a potential for one class ofpigment in the rods and tetra-chromatic colour vision. Mostmammals now are dichromaticand some are monochromatic(no colour or day vision and see-ing only at night). Primates areunique now in being trichromatic,with red, green and blue cones.Convincing evidence has beenput forward that this evolved tomake possible the gathering forfood of coloured fruits and youngleaves (17).

b) A variety of chromophores

Throughout the animal kingdomhundreds of visual pigments havebeen characterised by their ab-sorption maximum (γ max). Theγ max range from 432 nm for thegreen rod of the frog to 625 nmfor the red-absorbing cone of thegoldfish. The protein component,and not the chromophore, ismainly responsible for these dif-ferences.

The main chromophores of thevisual pigments are derived fromone or other of the two forms ofvitamin A; vitamin A1 (all-trans-retinol) or vitamin A2 (all-trans-3-dehydroretinol). The chromo-phores are respectively retinaland 3,4-didehydroretinal. Through-out the animal kingdom so faronly three other retinal congeners

all-trans-retinal

all-trans-

retinal

all-trans

retinyl ester

Light

RGR

all-trans-retinol

(Dark isomerisation)

IPM**

Photoreceptor

11-cis-retinal

11-cis-retinal

11-cis-retinol

11-cis-retinyl

ester

Opsin

LightVisual

pigment

(11-cis-retinal)

all-all-trans-trans-retinolretinolRPE*

* RPE = retinal pigment epithelium ** IPM = interphotoreceptor matrix

Figure 15. A scheme showing the newly described light-dependent, RGR-mediated isomerisation of all-trans to 11-cis-retinal in the retinal pigmentepithelium (dotted line). RGR = retinal G-protein-coupled receptor; (adaptedfrom reference 16, page 2099).


have been identified; all are ver-sions of hydroxyretinal and areespecially common in insects.These chromophores are thoughtto be derived from the cleavageof β-carotene to retinal followedby hydroxylation in the retina(18).

c) Freshwater fish and someamphibians

It has long been known that thevisual pigments of freshwater fishdiffer from those of marine fishand indeed almost all other ani-mals. Freshwater fish and someamphibians have 3-dehydro-retinal as chromophore and por-phyropsin for visual pigment withγ max near 540 nm. Most otheranimals have all-trans-retinal andrhodopsin, as in man, with γ maxnear 500 nm.

There is evidence that the reti-nas of freshwater fish and someamphibians can convert retinalinto 3-dehydroretinal. This pro-cess may be regulated largely byproperties of light in the naturalenvironment and is sometimesunder hormonal control. Age anddiet also play a part. The differ-ence in γ max of the differentchromophores appears to be anadaptation to permit fish to makeuse of the longer wavelengths oflight found in fresh water as com-pared with sea water.

Euryhaline fish, that is to saythose that tolerate a wide rangeof salinity in water, have a mix-ture of both rhodopsin and por-phyropsin. In the frog Ranapipiens, the chromophore in thetadpole is 11-cis-3-dehydro-retinal. In the adult this is re-placed by 11-cis-retinal.

Pinealgland

Optic chiasmaSuprachiasmatic nuclei

Post-ganglionicinnervation

Superior cervicalganglion

Projections tohypothalamic pituitary

control areas

Projections to brain stemand spinal cord

Opticnerve

Direct retinohypothalamicprojection

d) Fruit fly (Drosophila melano-gaster) and other flies

It is reported recently that thevisual pigment chromophore ofthis and possibly other flies is 3-hydroxyretinal and that this arisesfrom cleavage of β-carotene toretinal followed by hydroxylation(18). It is suggested that this allgoes on in the retinas.

7. PhotoentrainmentThis term is applied to the phe-nomenon whereby the regulardaily change in the quantity andquality of light that enters theeyes regulates a wide variety of

metabolic processes throughoutthe body, known as the circadianrhythm or biological clock (19). Inmammals this clock is locatedwithin a paired nucleus in thebrain above the crossing of theoptic nerves, the suprachiasmaticnucleus or SCN (Figure 16). Un-til recently little attention hasbeen paid to the way in whichlight is captured and processedby the eyes to bring aboutphotoentrainment. It was usuallyassumed that this was done bythe ordinary photoreceptors, therods and cones.

Studies on mice with genetic de-fects and patients with eye dis-

Figure 16. The suprachiasmatic nuclei (SCN) are located in the brainabove the crossing of the optic nerves. The neuronal acrtivity of thispaired nucleus operates with a 24-hour rhythmicity and is at the centreof the mammalian circadian clock. Adapted from William’s Textbook ofEndocrinology, 1992, page 168.


CHO

COOH

CHO

CH2OH

all-trans-retinol

visual

signal

alcohol dehydrogenase

transcriptional

signal

all-trans-retinaldehyde

11-cis-retinaldehyde

hν

all-trans-retinoic acid

aldehyde

dehydrogenase

isomerisation in the

retinal pigment epithelium

ease that caused loss of visionwithout affecting the circadiansystem suggested that theremight be separate photo-receptors for this function. Re-cently an expansive photorecep-tive “net” in the inner retina of themouse has been discovered con-sisting of melanopsin-containingretinal ganglion cells (20).Melanopsin is the only opsinknown to exist in the retinal gan-glion cell layer. If this, and noother, is the photoreceptive netfor the circadian system thenphotoentrainment is not part ofour story because it does not in-volve a relative of vitamin A. Thechromophore is melanin in thiscase. Confirmation of this infer-ence comes from a recent studyin mice mutated in plasma reti-nol-binding protein, made defi-cient in vitamin A and tested forphotic induction of gene expres-sion in the SCN (21). After 10months on the vitamin A-free diet

the eyes of most mice containedno detectable retinal. Photic sig-nalling to the SCN was fully in-tact, making it unlikely that thisprocess is mediated by a retinal-dependent receptor.

8. Nuclear retinoidreceptors

This function of the relatives ofvitamin A is probably the mostsurprising of all. Twenty years orso ago there was no firm evi-dence for the mechanisms be-hind the functions of vitamin A atthe cellular level. We had to relyon deducing this from evidenceprovided by the deficiency state.It was very clear that vitamin A insome form played a vital role insuch processes as development,cell proliferation and differentia-tion. The fundamental mecha-nism of action of retinoic acid incell differentiation was clarified

with the discovery of the firstretinoic acid receptor, RAR (nowRAR-α 1), a nuclear transcriptionfactor shown to be activated byall-trans-retinoic acid. At presentsix retinoid receptors of RAR andRXR gene subfamilies have beenidentified, belonging to the largersuperfamily of steroid/thyroid/retinoid hormone nuclear tran-scription factors. Detailed infor-mation has been provided in nu-merous reviews (22, 23).

Nearly all cells express at leastone member of the RAR andRXR subfamilies. Hundreds ofgenes have been shown to beinvolved and the control retinoicacid exerts over tissue and organdevelopment is being made in-creasingly clear (24).

Among the multitude of emerg-ing functions of retinoic acid a sin-gle example in the developingeye of the embryo may be out-

Figure 17. A scheme of vitamin A usage in the eye illustrating the link between its roles in vision and in transcrip-tional control. As the regeneration of 11-cis-retinal takes place in the retinal pigment epithelium (see Figure 15),some of the all-trans-retinal, released from rhodopsin, is converted to the transcriptional activator retinoic acid;(adapted from reference 25).


lined to illustrate something of theimportance of this field for humanhealth and disease in the future(25). The eye is known to be oneof the regions of the developingembryo that is richest in retinoicacid. Several alcohol dehydroge-nase enzymes are present in theretina and they are responsiblefor synthesising retinoic acid lo-cally. This they do in such a waythat the concentration of retinoicacid forms a gradient of concen-tration greatest at the ventral partand least at the dorsal. Gradiantsalso occur over time. In the ma-ture retina aldehyde dehydro-genase expression persists butthe amount of retinoic acid syn-thesised varies and is influencedby ambient light levels (Figure17). This phenomenon is due tochanging levels of retinal, whichis released in the retinas of ver-tebrates from illuminated rho-dopsin to be regenerated else-where, as mentioned previously.In the invertebrate retina all-trans-retinal remains covalentlybound to opsin. It is regeneratedthere by light that is of a differentwavelength from that of the lightof excitation. Consequently thereis a mechanism whereby lightcan directly influence gene ex-pression! Even here a relative ofvitamin A is once again bound upwith light in its function.

References

1. von Luntig J, Vogt K. Filling the gapin vitamin A research. Molecular iden-tification of an enzyme-cleaving β-carotene to retinal. J Biol Chem2000, 275: 11915-11920

2. Britton G. Structure and propertiesof carotenoids in relation to function.FASEB J 1995, 9: 1551-1558

3. Anon. Electromagnetic radiation.Encyclopaedia Britannica Macro-paedia, vol 18, 15th ed. Encyclopae-dia Britannica Inc, Chicago, 1999, pp195-211

4. Lodish H, Baltimore D, Berk A et al.Molecular cell biology, chapter 18, Anoverview of photosynthesis. 3rd ed,Scientific American Books, NewYork, 1995

5. Armstrong GA, Hearst JE. Geneticsand molecular biology of carotenoidpigment biosynthesis. FASEB J1996, 10: 228-237

6. Stryer L. Biochemistry. 4th ed., chap-ter 26, Freeman, New York, 1995, pp653-782

7. Karl DM. Hidden in a sea of mi-crobes. Nature 2002, 415: 590-591

8. Demmig-Adams B, Gilmore AM,Adams III WW. In vivo functions ofcarotenoids in higher plants. FASEBJ 1996, 10: 403-412

9. Krinsky NI. Carotenoids as antioxi-dants. Nutrition 2001, 17: 815-817

10. Seddon JM, Ajani UA, Sperduto RDet al. Dietary carotenoids, vitaminsA, C, and E, and advanced age-re-lated macular degeneration. J AmMed Assoc 1994, 172: 1413-1420

11. Wolf G. The enzymatic cleavage ofβ-carotene: end of a controversy.Nutr Revs 2001, 59: 116-118

12. Hamilton WD, Brown SP. Autumntree colours as a handicap signal.Proc Roy Soc B 2001, 268: 1489-1493

13. Watson JD, Hopkins NH, RobertsJW, Steitz JA, Weiner AM. Molecu-lar biology of the gene, vol 2,Benjamin/Cummings, Menlo Park,California, 1994, pp1154-1156

14. Margolis L, Sagan D. What is life?Weidenfeld and Nicolson, London,1995

15. Stryer L. Biochemistry, 4th ed. Free-man, New York, 1995, pp 318-320

16. Pepperberg DR, Crouch RK. An illu-minating new step in visual-pigmentregeneration. Lancet 2001, 358:2098-2099

17. Sumner P (2002). Colour vision: whyare we primates unique? Eye News8: 48-60.

18. Seki T, Isono K, Ozkaki K et al. Themetabolic pathway of visualchromophore formation in Drosophilamelanogaster. Eur J Biochem 1998,257: 522-527

19. Foster R, David-Gray Z, Lucas R.Eye, light, the eye, and the regula-tion of biological time. Eye News2001, 7: 24-30

20. Provencio I, Rollage MD, CaastrucciAM. Photoreceptive net in the mam-malian retina. Nature 2002, 415: 493

21. Thompson CL, Blaner WS, VanGelder RN et al. Preservation of lightsignaling to the suprachiasmatic nu-cleus in vitamin A-deficient mice.Proc Nat Acad Sci 2001, 98: 11708-11713

22. Kastner P, Chambon P, Leid M. Roleof nuclear retinoic acid receptors inthe regulation of gene expression. In:Vitamin A in health and disease, edR. Blomhoff. Dekker, New York,1994, pp 189-238

23. Kliewer SA, Umesono K, Evans RMet al. The retinoid X receptors: modu-lators of multiple hormonal signalingpathways. In: Vitamin A in health anddisease, ed R. Blomhoff. Dekker,New York, 1994, pp 239-255

24. Lee S-H, Fu KK, Hui JN et al. Nog-gin and retinoic acid transform theidentity of avian facial prominences.Nature 2001, 414: 20-27

25. Dräger UC, Wagner E, McCaffery etal. Aldehyde dehydrogenases in thegeneration of retinoic acid in the de-veloping vertebrate: a central role ofthe eye. J Nutr 1998, 128: 463S-466S

26. Cormack DH. Ham’s Histology, 9th

ed. 1987, J.B.Lippincott, Philadelphia

Please update your address and help toavoid unnecessary work and expenses.


Knowledge that vitamin A playsan important role in vision can betraced back approximately 3500years to writings in Egyptian tem-ples that indicate Egyptian phy-sicians prescribed the topical useof ox liver, a source rich in vita-min A, as a means for curing nightblindness. Scientific investiga-tions into vitamin A actions in vi-sion were initiated in the late 19th

century and reached an apogeewith the award of a Nobel Prizein 1967 to George Wald (1). Thework of Wald and many other in-vestigators had established bythe early 1960s that the 11-cis-retinal form of vitamin A servedas the chromophore for the visualpigment rhodopsin. The visualcycle of vitamin A as it was un-derstood at the time of the awardof the Nobel Prize to Wald isshown in Figure 1. Figure 1 is re-produced directly from the writ-ten text of Wald’s Nobel Prize lec-ture (1). This early work definedthe metabolism and transportprocesses that take place in theretinal pigment epithelium (RPE)and photoreceptors that are nec-essary to make 11-cis-retinalavailable for visual pigment for-mation. These processes werecollectively known as the visualcycle of vitamin A. It appeared inthe late 1960s through the mid-1990s that the knowledge regard-ing the visual cycle of vitamin Awas fairly complete. Most of theenzymatic processes involved inthe visual cycle were thought tohave been identified. It seemed

that the sole important questionthat Wald and his contemporar-ies failed to answer was how theall-transform of vitamin A, whichis present in the circulation andall tissues outside of the eye, isisomerised to the 11-cis- formthat is needed in the eye for vi-sion. By the late 1980s, this ques-tion too appeared to have beenanswered and research interestin the visual cycle waned (2, 3).However, owing to the use ofadvanced molecular and genetic

approaches to study vision, it hasbecome clear that the visual cy-cle of vitamin A is far more com-plex than had been previouslythought. In the last decade, manynovel gene products (proteins)that play essential roles in thevisual cycle have been identified.Some of these novel genes andother genes encoding known pro-teins involved in the visual cyclehave been identified as loci forrecognised heritable eye dis-eases.

Vitamin A and the visual cycle:An increasingly complex storyChristine M. Donmoyer, Katherine Lai and William S. Blaner, Department of Medicine,College of Physicians and Surgeons, Columbia University, New York, NY 10032 U.S.A.

Figure 1. Visual cycle as depicted by Wald (1968). DPN and TPN refer tocofactors NAD+ and NADH.


The isomerisation ofall-trans-vitamin A to11-cis-vitamin AThe one great-unresolved ques-tion regarding the visual cycle ofvitamin A that remained unan-swered from the era of Wald washow the eye generates 11-cis-retinal (1). Starting in 1987, aseries of reports were publishedthat indicated that 11-cis -retinolis formed from all-trans-retinylester through the enzymatic cou-pling of ester hydrolysis withisomerisation of the resultant all-trans-retinol to its 11-cis-isomer(2, 3). The retinal pigment epithe-lium (RPE) enzyme that cata-lyses this reaction was referredto as the isomerohydrolase (4).Although the enzyme had notbeen purified or cloned, it wasgenerally accepted that theisomerohydrolase was responsi-ble for catalyzing 11-cis -retinolformation within the eye (4). How-ever, this view began to be ques-tioned in 1998 with the publica-tion of the characterisation ofRPE65 knockout mice; thesemice were generated through thetargeted disruption of the gene forRPE65 (5). The deletion of thegene for RPE65 rendered thesemutant mice blind and unable toconvert all-trans- forms of vitaminA to 11-cis-isomers. RPE65 hadbeen initially described severalyears earlier as a protein that isexpressed solely in the RPE inthe eye but no physiological func-tion could be assigned to the pro-tein. The phenotype of theRPE65 knockout mice sugges-ted that RPE65 could be theisomerohydrolase; howeverwhen the purified protein wasstudied, still no definitive evi-dence could be obtained thatRPE65 acted as an isomero-

hydrolase. Thus, the absence ofRPE65 results in a failure to form11-cis-retinal from all-trans-vita-min A forms yet RPE65 does notact catalytically as an isomero-hydrolase.

More recently, another RPE-spe-cific protein, retinal G-protein-coupled receptor (RGR) wasidentified and demonstrated to beimportantly involved in the light-

dependent formation of 11-cis-retinal from all-trans-retinal (6, 7).Exposure of all-trans-retinalbound to RGR to light generates11-cis-retinal (6, 7). Interestingly,RGR-knockout mice regeneratevisual pigment more slowly, whenexposed to a continuous low levelof light, than do wild type mice,but in darkness the rates of rodvisual-pigment regeneration arethe same for RGR-knockout and

all-trans-retinal

all-trans-

retinal

all-trans

retinyl ester

Light

RGR

all-trans-retinol

all-trans-retinoldehydrogenase

RPE65 (?)

(Dark isomerisation)

IPM**

Photoreceptor

11-cis-retinal

11-cis-retinal

11-cis-retinaldehydrogenase

11-cis-retinol

11-cis-retinyl

ester

Opsin

LightVisual

pigment

(11-cis-retinal)

all-all-trans-trans-retinolretinolRPE*

LRAT

* RPE = retinal pigment epithelium ** IPM = interphotoreceptor matrix

Figure 2. Current perspective of the visual cycle of vitamin A from Pepperbergand Crouch (2001). RGR, retinal G-protein-coupled receptor; LRAT,lecithin:retinol acyltransferase.


wild-type mice (6, 7). It is nowthought that the light-dependentisomerisation of all-trans- to11-cis-retinal catalysed by RGRmost likely operates in concertwith a dark pathway of 11-cis-reti-nol from all-trans-retinol thatprobably involves the actionRPE65 (8). Thus, based on theserecent data, it is now believedthat two distinct isomerisationpathways operate as part of thevisual cycle of vitamin A. Our cur-rent understanding of the visualcycle of vitamin A is summarisedin Figure 2.

New understandingof other enzymesinvolved in trans-forming vitamin A inthe visual cycleThree enzymes proposed tohave essential actions in thevisual cycle of vitamin A havebeen studied to varying degreesin the last decade. Two of these,11-cis-retinol dehydrogenase(also called RDH5 and cis-reti-nol dehydrogenase) and leci-thin:retinol acyltransferase(LRAT) are present in the RPEand the other, all-trans-retinoldehydrogenase, is present in thephotoreceptors (see Figure 2).

11-cis-Retinol dehydrogenasecatalyses the conversion of 11-cis-retinol to 11-cis-retinal, whichis needed for visual pigment for-mation (4). Since 11-cis-vitaminA forms are present in only theeye and although it was originallyreported that this enzyme is eye-specific (9, 10), it is now recog-nized that the enzyme is alsopresent in kidney, liver, testis aswell as other tissues. It has beenproposed that outside of the eye

this enzyme plays a role in gen-erating 9-cis-retinoic acid, whichis needed for regulating transcrip-tion, and in the metabolism ofsteroids (11). Interestingly, mu-tant mice completely lacking 11-cis-retinol dehydrogenase dis-play delayed dark adaptation buthave otherwise normal vision(12). This observation has beentaken to suggest that other en-zymes are present in the RPEable to catalyse 11-cis-retinalformation. Indeed, this also ap-pears to be the case for humans,

since mutations in the human 11-cis-retinol dehydrogenase gene donot result in complete blindness(see below for more details) (13).

LRAT catalyses the formation ofretinyl esters through trans-esterification of all-trans-retinolwith a fatty acid group taken fromphosphatidyl choline present inthe membranes of the RPE cell(3, 4, 14). This enzyme, too, isfound in tissues outside of theeye and is thought to play an es-sential role in the esterification of

Table I. Mutations in vitamin A-related genes responsible for humanretinal diseases

Gene/protein Disease Clinical symptoms

Retinal pigment Leber’s congenital Severely reducedepithelial protein 65 amaurosis, early- rod function,(RPE65) (27) onset retinal dystrophy blindness

ATP-binding Stargardt’s disease, Central vision losscassette transporter cone-rod dystrophy, due to lipofuscinin retina (ABCR) retinitis pigmentosa, accumulation(21) age-related macular

degeneration

11-cis-Retinol Recessive fundus Stationary nightdehydrogenase albipunctatus, late- blindness and(RDH5) (13) onset recessive cone delayed dark

dystrophy adaptation

Cellular Recessive retinitis Peripheral visionretinaldehyde- pigmentosa, lossbinding protein recessive retinitis(CRalBP) (28) punctata albescens

Lecithin:retinol Severe early–onset Severe retinalacyltransferase recessive retinitis dystrophy(LRAT) (18) pigmentosa

Retinal G-protein- Recessive retinitis Peripheral visioncoupled receptor pigmentosa loss(RGR) (17)

Retinol-binding Recessive RPE Night blindnessprotein (RBP) degeneration with RPE atrophy(24,25) and reduced acuity


dietary retinol in the small intes-tine and in the storage of retinylester in the liver (14). In the eye,LRAT action is needed to gener-ate all-trans-retinyl ester poolsthat can be used by theisomerohydrolase for generationof 11-cis-retinol (14).

The photoreceptor enzyme, all-trans-retinol dehydrogenase, thatcatalyses the formation of all-trans-retinol from all-trans-retinalformed upon bleaching of thevisual pigment rhodopsin hasbeen recently cloned and char-acterised (15). This enzyme spe-cifically requires all-trans-vitaminA forms as substrates and will notcatalyse the inverconversion of11-cis-vitamin A forms. It is pres-ently unclear whether this en-zyme has an important physi-ological role outside of the eyeand the visual cycle.

Genetic eye dis-eases and proteinsinvolved in vitaminA metabolism in theeyeMany of the genes encoding pro-teins that are active in maintain-ing the visual cycle are also as-sociated with genetic eye dis-eases (8, 13, 16-21). A partial list-ing of these genes is given inTable I. As can be seen from Ta-ble I, the genes for RPE65, RGR,11-cis-retinol dehydrogenaseand LRAT have all been identi-fied as sites for mutations thatgive rise to impaired vision orblindness. Mutations in RPE65are associated with certain formsof Leber’s congenital amaurosisand account for approximately15% of the disease in NorthAmerica (8, 16). In a dog model

of Leber’s congenital amaurosisarising due to RPE65 mutation,gene therapy with a recombinantadeno-associated virus carryingwild-type RPE65 has beenshown to restore vision (22).RGR gene mutations have beenfound in some patients with retini-tis pigmentosa (17). Mutations inthe gene for 11-cis-retinol dehy-drogenase have been associatedwith fundus albipunctatus, a formof stationary night blindnesscharacterised by a delay in theregeneration of cone and rodphotopigments (13). LRAT genemutations are associated withearly-onset severe retinal dystro-phy (18). It is interesting to notethat, unlike RPE65 or RGR, LRATis expressed widely throughoutthe body (including in the liver,intestine and numerous other tis-sues), yet mutations associatedwith LRAT seem to result solelyin ocular disease.

Several proteins that are presentin the retina and important formaintaining the visual cycle havealso recently been cloned andcharacterised. One of these pro-teins, ABCR, is an ATP-bindingcassette transporter present inthe rims of photoreceptor outersegment discs (19-21). Thismembrane transport protein isproposed to play a role in pump-ing all-trans-retinal from the discinterior after light exposure andin eliminating the vitamin A de-rivatives and lipofuscin precur-sors A2PE-H2 and A2PE fromphotoreceptor outer segments(19-21). Mutations in the ABCRgene have been shown to be re-sponsible for Stargardt’s disease,a blinding disorder that is char-acterized by delayed dark-adapta-tion and accelerated deposition oflipofuscin in the RPE (19-21).

Other recent studies indicate thatmutations that influence the de-livery of vitamin A to the eye canalso give rise to ocular disease.Plasma retinol-binding protein(RBP) is the sole circulatingtransport protein for vitamin A andit is thought that the preponder-ance of the vitamin A deliveredto the eye and other tissues isdelivered via RBP (23). Two sis-ters have been identified in Ger-many who reportedly lack anycirculating RBP (24, 25). Theseyoung women display compoundRBP mutations that give rise tonight blindness and impaireddark adaptation (24, 25). RBPknockout mice similarly displayan impaired vision phenotypethat can be reversed if the miceare provided significant amountsof vitamin A in their diets (26).Thus, as was the case for LRATmutations mentioned above,mutations in RBP, a protein thatis responsible for delivering vita-min A to all tissues in the body,seem to be manifested solelythrough impairments in vision.

SummaryOverall, in the past decade therehas been tremendous growth inour understanding of the genesand proteins that are responsiblefor maintaining the visual cycleof vitamin A. It is clear that thevisual cycle is far more complexand involves many more proteinspecies than was ever suspectedby Wald and his contemporaries.In addition, it is clear that manyof the proteins involved in thevisual cycle can be sites for mu-tations that give rise to heritableeye diseases. After many yearsof relatively little research inter-est in the visual cycle, this re-search area is again one of greatactivity. The research cycle


seems to have rotated back to aperiod when significant newinsights into the actions of vita-min A in the visual cycle are againbeing made. Indeed, the presenttime is one where a whole newlayer of complexity has beenadded to our basic understand-ing of the visual cycle ofvitamin A.

References

1. Wald G. The molecular basis ofvisual excitation. Nature 1968, 219;800-807

2. Bernstein PS, Law WC, Rando RR.Isomerization of all-trans-retinoids to11-cis-retinoids in vitro. Proc NatlAcad Sci USA 1987, 84: 1849-1853

3. Rando RR. Membrane phospholipidsas an energy source in the opera-tion of the visual cycle. Biochemistry1991, 30: 595-602

4. Saari JC. Retinoids in photosensitivesystems. In: The Retinoids: Biology,Chemistry, and Medicine, 2nd Edition,pp. 351-386, Sporn, M.B., Roberts,A.B., and Goodman, D.S. eds. 1994,Raven Press Ltd., New York

5. Redmond TM, Yu S, Lee E, Bok Dl,Hamasaki D, Chen N, Goletz P, MaJX, Crouch RK, Pfeifer K. RPE65 isnecessary for production of 11-cis-vitamin A in the retinal visual cycle.Nat Genet 1998, 20: 344-351

6. Chen P, Hao W, Rife L, Wang XP,Shen D, Chen J, Ogden T, VanBoemel GB, Wu L, Yang M, FongHFW. A photic visual cycle of rho-dopsin regeneration is dependent onRgr. Nat Genet 2001, 28: 256-260

7. Chen P, Lee TD, Fong HKW. Inter-action of 11-cis-retinol dehydroge-nase with the chromophore of reti-nal G protein-coupled receptor opsin.J Biol Chem 2001, 276: 21098-21104

8. Pepperberg DR, Crouch RK. An illu-minating new step in visual-pigmentregeneration. Lancet 2001, 358:2098-2099

9. Driessen CA, Janssen BP, WinkensHJ, van Vugt AH, de Leeuw TL,Janssen JJ. Cloning and expressionof a cDNA encoding bovine retinalpigment epithelial 11-cis-retinol de-hydrogenase. Invest Ophthalmol VisSci 1995 36: 1988-1996

10. Simon A, Hellman U, Wernstedt C,Eriksson U. The retinal pigment epi-thelial-specific 11-cis-retinol dehydro-genase belongs to the family of shortchain alcohol dehydrogenases. J BiolChem 1995, 270: 1107-1112

11. Mertz JR, Shang E, Piantedosi R,Wei S, Wolgemuth DJ, Blaner WS.Identification and characterization ofa stereospecific human enzyme thatcatalyzes 9-cis -retinol oxidation. JBiol Chem 1997, 272: 11744-11749

12. Shang E, Lai K, Packer AJ, Paik J,Blaner WS, de Morais Vieira M,Gouras P, Wolgemuth DJ. Targeteddisruption of the mouse cis-retinoldehydrogenase gene: visual andnonvisual functions. J Lipid Res2002, 43: 590-597

13. Liden M, Romert A, Tryggvason K,Persson B, Eriksson U. Biochemicaldefects in 11-cis-retinol dehydroge-nase mutants associated with fundusalbipunctatus. J Biol Chem 2001,276: 49251-49257

14. Ruiz A, Bok D. Molecular characteri-zation of lecithin-retinol acyltrans-ferase. Methods Enzymol 2000, 316:400-413

15. Rattner A, Smallwood PM, NathansJ. Identification and characterizationof all-trans-retinol dehydrogenasefrom photoreceptor outer segments,the visual cycle enzyme that reducesall-trans-retinal to all-trans-retinol. JBiol Chem 2000, 275: 11034-11043

16. Saari JC. The sights along route 65.Nat Genet 2001, 29: 8-9

17. Morimura H, Saindelle-RibeaudeauF, Berson E, Dryja TP. Mutations inRGR, encoding a light-sensitiveopsin homologue, in patients withretinitis pigmentosa. Nat Genet 1999,22: 393-394

18. Thompson DA, Li Y, McHenry CL,Carlson TJ, Ding X, Sieving PA,Apfelstedt-Sylla E, Gal A. Mutationsin the gene encoding lecithin retinolacyltransferase are associated withearly-onset severe retinal dystrophy.Nat Genet 2001, 28: 123-124

19. Weng J, Mata NL, Azarian SM,Tzekov RT, Birch DG, Travis GH.Insights into the function of Rim pro-tein in photoreceptors and etiologyof Stargardt’s disease from the phe-notype in abcr knockout mice. Cell1999, 98: 13-23

20. Mata NL, Tzekov RT, Liu X, Weng J,Birch DG, Travis GH. Delayed dark-adaptation and lipofuscin accumula-tion in abcr +/- mice: implications forinvolvement of ABCR in age-related

macular degeneration. Invest Oph-thalmol Vis Sci 2001, 42: 1685-1690

21. Allikmets R, Singh N, Sun H, ShroyerNF, Hutchinson A, Chidambaram A,Gerrard B, Baird L, Stauffer D, PeifferA, Rattner A, Smallwood P, Li Y,Anderson KL, Lewis RA, Nathans J,Leppert M, Dean M, Lupski JR. A pho-toreceptor cell-specific ATP-bindingtransporter gene (ABCR) is mutatedin recessive Stargardt macular dys-trophy. Nat Genet 1997, 15: 236-246

22. Acland GM, Aguirre GD, Ray J,Zhang Q, Aleman TS, Cideciyan AV,Pearce-Kelling SE, Anand V, Zeng Y,Maguire AM, Jacobson SG,Hauswirth WW, Bennett J. Genetherapy restores vision in a caninemodel of childhood blindness. NatGenet 2001, 28: 92-95

23. Gottesman ME, Quadro L, BlanerWS. Studies of vitamin A metabolismin mouse model system. Bioessays2001, 23: 409-419

24. Biesalski HK, Frank J, Beck SC,Heinrich F, Illek B, Reifen R, Gollnick,H, Seeliger MW, Wissinger B, Zren-ner E. Biochemical but not clinical vi-tamin A deficiency results from muta-tions in the gene for retinol binding pro-tein. Am J Clin Nutr 1999, 69: 931-936

25. Seeliger MW, Grimm C, Stahlberg F,Friedburg C, Jaissle G, Zrenner E,Guo H, Reme CE, Humphries P,Hofmann F, Biel M, Fariss RN,Redmond TM, Wenzel A. Phenotypein retinol deficiency due to a heredi-tary defect in retinol binding proteinsynthesis. Invest Ophthalmol Vis Sci1999, 40: 3-11

26. Quadro L, Blaner WS, Salchow DJ,Vogel S, Piantedosi R, Gouras P,Freeman S, Cosma MP, ColantuoniaV, Gottesman ME. Impaired retinalfunction and vitamin A availability inmice lacking retinol-binding protein.EMBO J 1999, 18: 4633-4644

27. Gu SM, Thompson DA, SrikumariCR, Lorenz B, Finckh U, Nicoletti A,Murthy KR, Rathmann M, Kumar-amanickavel G, Denton MJ, Gal A.Mutations in RPE65 cause auto-somal recessive childhood severeonset retinal dystrophy. Nat Genet1997, 17: 194-197

28. Maw MA, Kennedy B, Knight A,Bridges R, Roth KE, Mani EJ,Mukkadan JK, Nancarrow D, CrabbJW, Denton MJ. Mutations in thegene encoding cellular retinalde-hyde-binding protein in autosomal re-cessive retinitis pigmentosa. NatGenet 1997, 17: 198-200


Effects of processing and storage on foodcarotenoidsDelia B. Rodriguez-Amaya, Departamento de Ciência de Alimentos, Faculdade deEngenharia de Alimentos, Universidade Estadual de Campinas, C.P. 6121, 13083-970Campinas, SP, Brasil

IntroductionMany carotenogenic foods areseasonal and processing at peakharvest is necessary to minimiselosses, make the products avail-able all year round and permittransportation to places otherthan the site of production.Processing and storage of foodsshould, however, be optimised toprevent or reduce harmful effectsand accentuate the benefits.

Alteration or loss of carotenoidsduring processing and storage offoods occur through physical re-moval (e.g. peeling), geometricalisomerisation and enzymatic ornon-enzymatic oxidation. Neces-sary measures should be takento ensure maximum retention ofcarotenoids. Although industrialprocessing is more oftenfocalised, losses on home prepa-ration can also be, at times evenmore, considerable. On the otherhand, processing may enhancebioavailability.

Retention ofcarotenoids duringprocessing andstorage

Considerable retention or loss ofcarotenoids during processingand storage of food has been re-ported in numerous papers. How-

ever, data are somewhat conflict-ing and often difficult to interpretbecause of the following reasons:(a) processing and storage con-ditions are not, or are only par-tially, described; (b) differentfoods are processed differently,making comparisons of process-ing methods difficult; (c) differentconditions (e.g. time and tem-perature) are used for the samemethod of processing; (d) theprocedure followed for calculat-ing losses is not specified or cal-culation is faulty (1). Additionally,an inherent problem that shouldnot be overlooked is the possi-bility of isomerisation and oxida-tion of carotenoids taking placeduring analysis and/or duringstorage of samples prior to analy-sis. These reactions may be er-roneously attributed to theprocessing or storage of foods.But despite some experimentalinadequacies and discrepanciesin results, some conclusions canbe drawn (1):• Carotenoid biosynthesis may

continue, raising the carotenoidcontent in fruits, fruit vegetablesand root crops even after har-vest, provided these plant ma-terials are kept intact and arenot treated in any way thatwould inactivate the enzymesresponsible for carotenogen-esis. In leaves and other veg-etables, post-harvest degrada-tion of carotenoids appears toprevail, especially at high stor-

age temperature and underconditions that favour wilting.

• Carotenoids are naturally pro-tected in plant tissues; cutting,shredding, chopping and pulp-ing of fruits and vegetables in-crease exposure to oxygen andbring together carotenoids andenzymes that catalyse carote-noid oxidation.

• The stability of carotenoids dif-fers in different foods, evenwhen the same processing andstorage conditions are used.Thus, optimum conditions forcarotenoid retention duringpreparation/processing differfrom one food to another. Carot-enoids per se have differentsusceptibilities to degradation.

• The major cause of carotenoiddestruction during processingand storage of foods isenzymatic or non-enzymaticoxidation. Isomerisation oftrans-carotenoids to the cis-iso-mers, particularly during heattreatment, alters their biologicalactivity and discolours foods,but not to the same extent asoxidation. Enzymatic degrada-tion of carotenoids may be amore serious problem than ther-mal decomposition in manyfoods.

• Reported increases in caroten-oid content during cooking orthermal processing are notlikely to be true increases butare artefacts of the analytical/calculation procedure, due to


loss of carotenoids in fresh sam-ples because of enzymatic ac-tivity during sample preparationfor analysis, greater extractabil-ity of carotenoids from proc-essed samples, and unac-counted loss of water andleaching of soluble solids dur-ing processing.

• In home preparation, losses ofcarotenoids generally increasein the following order: micro-waving < steaming < boiling <sautéing. Deep-frying, pro-longed cooking, combination ofseveral preparation and cook-ing methods, baking and pick-ling all result in substantiallosses of carotenoids.

• Whatever the processingmethod chosen, retention of ca-rotenoid decreases with longerprocessing time, higher pro-cessing temperature and cut-ting or puréeing of the food. Re-ducing processing time andtemperature, and the time lagbetween peeling, cutting or pur-éeing and processing improvesretention significantly. High-tem-perature, short-time processingis a good alternative.

• The heat treatment in blanch-ing may provoke some lossesof carotenoids, but the inactiva-tion of oxidative enzymes willprevent further and greaterlosses during holding beforethermal processing, slowprocessing and storage.

• Freezing (especially quick-freezing) and frozen storagegenerally preserve the carot-enoids, but slow thawing can bedetrimental, particularly whenthe product has not been prop-erly blanched.

• Peeling and juicing result in sub-stantial losses of carotenoids,often surpassing those of heattreatment.

• Traditional sun-drying, althoughthe cheapest and most acces-sible means of food preserva-tion in poor regions, causesconsiderable carotenoid de-struction. Drying in a solar dryer,even of simple and inexpensivedesign, can appreciably reducelosses. Protecting the food fromdirect sunlight also has a posi-tive effect.

• Natural or added antioxidantand sulfiting may reduce carot–enoid degradation.

• Exclusion of oxygen (e.g.through vacuum or hot filling,oxygen-impermeable packag-ing, inert atmosphere), protec-tion from light and low tempera-ture diminish carotenoid de-composition during storage.

Geometrical isom-erisation

Being highly unsaturated,carotenoids are prone to isomeri-sation and oxidation (Figure 1).Isomerisation of trans-carot-enoids, the usual configuration innature, to the cis-isomers is pro-moted by contact with acids, heattreatment and exposure to light.This results in some loss of col-our and alteration of biological ac-tivity. The principal cis-isomers ofβ-carotene are shown in Figure 2.

The release of organic acids dur-ing slicing or juicing of fruits issufficient to provoke trans-cisisomerisation. However, occur-

Figure 1. Possible scheme for the degradation of carotenoid.

trans-carotenoids

epoxy carotenoids

apocarotenoids

hydroxy carotenoids

low molecular mass

compounds

oxidation cis-carotenoids

isomerisation

oxidation


rence of this isomerisation hasbeen better demonstrated in ther-mal processing.

A 10–39% increase in the per-centage of total cis-isomers ofprovitamin A carotenoids wasobserved on heat treatment (can-ning) of several fruits and vegeta-bles (2). Canning of sweet potatocaused the largest increase, fol-lowed by processing of carrot,tomato juice, collard, tomato,spinach, peach and orange juice.The principal cis-isomers in pro-cessed red, yellow and orangefruits and vegetables were13-cis-(and 13’-cis-), although 9-cis- and 15-cis-isomers were alsodetected. In processed greenvegetables (in which β-carotenewas the only provitamin A caro-tenoid detected), 9-cis-β-carot-ene predominated, followed by13-cis-β-carotene, an unidentifiedcis-isomer and 15-cis-β-carotene.

Figure 2. Common geometrical isomers of β-carotene.

Table 1. Cis-trans-β-carotene isomer concentrations (µg/g dryweight) in raw and processed sweet potatoes

Treatment 13-Cis- All-Trans 9-Cis

Raw product 22 418 -Strips (2-min blanch 100ºC) 39 460 -Strips (10-min blanch 100ºC) 70 388 -Puree (lye peeled, Fitzmill comminutor with 0.06” screen) 25 461 -Steam injection (81ºC to gelatinise starch, hold 30 min) 34 461 -Steam injection (100ºC to inactivate amylases) 37 419Canned (still retort, 90 min at 116ºC) 57 323 11Dehydrated (drum dried at 160ºC at 25 rpm with contact time of 1.8–2 sec) 101 249 traceMicrowaved (full power for 7 min until internal temp. of 99ºC) 56 284 traceBaked (conventional oven at 191ºC for 80 min until internal temp. of 99ºC) 69 232 trace

Reference: Chandler and Schwartz (5)

All-trans-β-carotene

9-cis-β-carotene13-cis-β-carotene15-cis-β-carotene


The isomerisation pattern re-ported by Lessin et al. was alsoobserved in earlier studies, the13-cis- being the major cis-iso-mer in processed fruits and veg-etables, except in processedgreen vegetables in which the 9-cis- prevailed (3-5).

In sweet potatoes, heat inducedformation of 13-cis-β-carotene inthe different thermal treatmentsinvestigated, the quantity formedbeing related to the severity andlength of processing (Table 1) (5).Cis-isomers also increased dur-ing heating of carrot juice (6), 13-cis-β-carotene being formed inlargest amount, followed by 13-cis-lutein and 15-cis-α-carotene.

To minimise hydrolytic rancidityin the oil, red palm fruits are steril-ised immediately after harvest toinactivate lipases. This treatment(128ºC, 66 min) provokes sub-stantial isomerisation of α- andβ-carotene, as shown in Table 2for oils from Elais guineensis andE. oleifera fruits (7).

Although the cis-isomer levels ofβ-carotene in cooked (boiled and/or stir-fried) carrot, Indian egg-plant and squash were higherthan those of the correspondingraw vegetables, those of cookedbroccoli, green beans, okra andspinach were lower (8). Sinceboth cis- and trans-carotenoidsundergo oxidation, the latter find-ing could be a reflection of theturn-over of cis-β-carotene.

Lycopene was found to be rela-tively resistant to heat-inducedgeometrical isomerisation duringtypical food processing of toma-toes and related products (9). Invarious thermally processedproducts (juice, paste, soup,sauce), the lycopene cis-iso-mers amounted to 3.56–5.98%,compared to 4.16% in fresh to-mato and 5.37% in peeled to-mato, and the cis-isomer contentdid not reflect the severity of theheat treatment. On the otherhand, appreciable levels of β-carotene cis-isomers did form,the cis-isomer percentage rang-

ing from 55.57 to 85.85% in theprocessed products, comparedto 21.77% in the fresh tomatoand 23.83% in the peeled to-mato.

Enzymatic oxidationThe highly reactive, electron-richcarotenoid molecule suffers oxi-dation under food processing andstorage conditions, the magni-tude of which depends on thecarotenoids present, availableoxygen, exposure to light, tem-perature, presence of enzymes,metals, prooxidants and antioxi-dants.

Enzyme-catalysed oxidation canoccur in the steps prior to heattreatment, during peeling, slic-ing, pulping or juicing. Thus, it isrecommended that foods bethermally processed immedi-ately after these operations.Enzymatic oxidation can alsotake place in minimally proc-essed and in unblanched frozenfoods.

Table 2. Cis-trans isomers of β-carotene and α-carotene (µg/g) in palm fruit oils

From fresh fruits/From sterilised fruitsCarotenoid

E. guineensis E. guineensis E. guineensis E. oleiferaDura Dumpy Psífera Tenera

13-Cis-α-carotene 4.8/87 0.5/5.5 4.5/64 -/144

All-trans-α-carotene 296/228 18/14 164/94 425/342

13-Cis-β-carotene 12/200 8.2/63 13/129 61/352

All-trans-β-carotene 576/255 202/88 363/229 1026/400

9-Cis-β-carotene 12/179 1.2/55 1.7/53 -/241

Reference: Trujillo-Quijano et. al. (7)


Marketing minimally processedfruits and vegetables is an in-creasing trend, stimulated byconsumers’ demand for high-quality, nutritive, fresh-like andconvenient-to-use products.Since drastic processing condi-tions are not employed, minimallyprocessed products are expectedto retain fresh or fresh-like prop-erties and have good nutritivequality. However, tissue disrup-tion by cutting or shredding al-lows substrate/enzyme interac-tions and makes these productsmore susceptible to physiologi-cal/biochemical changes than in-tact raw commodities. Greaterexposure of plant components tooxygen also enhances oxidativedegradation.

In mini-peeled carrots packed inLDPE films and stored at 2ºC, α-carotene and β-carotene levelsdeclined 18 and 14%, respec-tively, within three days after mini-mal processing with no furtherlosses during 14 days of storage(10). In minimally processedJalapeño pepper rings packed inpolyethylene bags and stored at

4.4ºC, α-carotene and β-caro-tene decreased 31 and 24%, re-spectively, after three days insealed perforated bags (air at-mosphere) (11). With modifiedatmosphere (5% O2, 4% CO2),however, losses of thesecarotenoids amounted to only 4and 10%, respectively.

β-carotene, lutein, violaxanthinand neoxanthin concentrations,monitored during five days ofstorage at 7–9ºC were reduced14–42%, 19–32%, 12–20% and8–31%, respectively, in minimallyprocessed endive, kale (Table 3),spinach and a mixture of greenonion and parsley packed inpolyethylene bags (12). As wouldbe expected of an enzymatic re-action, losses of carotenoids oc-curred mainly in the first two daysof storage. Minimal processingconsisted of washing, trimming,cutting, washing in chlorinatedwater, draining (centrifugation)and packaging. Spinach (small-leaf type) consisted of wholeleaves, endive and kale wereshredded, parsley and onionwere finely chopped.

In frozen (-18ºC) Eugenia uniflorapulp, β-cryptoxanthin, γ-caroteneand lycopene were considerablyreduced during the first twomonths of storage at -15ºC, sta-bilising thereafter (13). The extentof loss was much greater thanthat usually seen in thermallyprocessed products. Moreover,carotenoid decomposition in thelatter products is usually insignifi-cant during the first severalmonths, increasing rapidly whenit ensues.

The β-carotene and lutein con-tents of unblanched andblanched (100ºC, 4 min) choppedgreen beans and intact Padrónpepper, all frozen at -22ºC, weremonitored over 12 months (14).Both pigments decreased con-siderably during the first monthin green beans packed in manu-ally sealed and vacuum-sealedpolyethylene bags. Lutein stabi-lised during the next 11 months;β-carotene decreased further inthe second month but stabilisedthereafter. The smaller overalldecrease of β-carotene in blan-ched beans was attributed to de-

Table 3. Carotenoid concentrations (µg/g) of minimally processed kale*

Time afterprocessing (days) β-Carotene Lutein Violaxanthin Neoxanthin

0 29a 45a 20a 13a

1 25b 37b 17b 9b

2 23b 35b,c 16b 9b

3 24b 33c 16b 9b

5 25b 33c 16b 9b

* Shredded kale packed in polyethylene bags, stored at 6–9ºC. Values in the same column with differ-ent letters are significantly different (p≤ 0.05); Reference: Hess and Rodriguez-Amaya (12).


activation of lipoxygenase. Re-duction of lutein, however, wasroughly the same for blanchedand unblanched beans. In con-trast, the β-carotene and luteinlevels in the frozen pepper fluc-tuated around more or less con-stant values over the 12 months.

Papaya slices without previoustreatment were vacuum-packedin plastic bags and frozen in air-blast freezer operating at -40ºC.The bags were left in the freezeruntil the center of the slicesreached -24ºC and then storedat -18ºC for 12 months (15). Thecarotenoid content decreasedsignificantly, the reduction beingmarkedly higher in the femalepapaya slices than the hermaph-rodite papaya slices. The differ-ence was attributed to greaterenzymatic activity in the femalepapaya slices.

Non-enzymaticoxidation

In contrast to the wealth of infor-mation on lipid oxidation,present-day knowledge of carot-enoid oxidation is still fragmen-tary. It is often accompanied byisomerisation, both cis- andtrans-isomers being subject tooxidation (Figure 1). It is gener-ally accepted that the initialstages of oxidation involveepoxidation and cleavage toapocarotenals (Figure 1). Subse-quent fragmentations result incompounds of low molecularmasses, similar to those pro-duced in fatty acid oxidation. Nowdevoid of colour and biologicalactivity, these compounds con-tribute to the desirable flavour ofwine and tea but can be respon-sible for the off-flavour of dehy-drated carrot. Full structural elu-

cidation of the intermediate andfinal products of the oxidativeprocess, as well as delineation ofthe mechanisms for their forma-tion, are urgently needed.

Epoxidation and transformationof the 5,6-epoxide groups to the5,8-furanoid groups of β-caroteneis illustrated in Figure 3. Introduc-tion of an epoxide group at oneof the β-rings reduces the vita-min A activity by about half, whilethe epoxidation of both ringseliminates this activity.

Transformation of the xanthophyllviolaxanthin is often observed infood processing (Figure 4). Inmango (cultivar Tommy Atkins)slices, the carotenoid composi-tion was practically maintainedduring processing (16). The onlysignificant change was the in-crease in luteoxanthin, compat-ible with the conversion of 5,6-

Figure 3. Formation of epoxy carotenoids from β-carotene.

All-trans-β-carotene

O

All-trans-β-carotene-5,6-epoxide All-trans-β-carotene-5,8-epoxide

All-trans-β-carotene-5,6,5',8'-diepoxide



O

O

O

O

O

O

O


to 5,8-epoxide. More evidentchanges occurred on processingmango (cultivar Golden) purée.Auroxanthin, not found in thefresh fruit, appeared whileviolaxanthin and luteoxanthindecreased, again reflecting thetransformation of 5,6- to 5,8-epoxide. In commercially pro-cessed mango juice (threebrands), the notoriously unstableviolaxanthin, the principal carot-enoid of the major mangocultivars in Brazil, was not de-tected while auroxanthin wasfound in appreciable amount (17).

In bottled papaya (cultivar Solo)purée, no significant loss ofβ-carotene, ζ-carotene, γ-caro-tene and lycopene occurred dur-ing processing (18). There wasa small statistically significant de-crease in β-cryptoxanthin andcryptoflavin, an epoxy derivativeof β-cryptoxanthin, appeared af-

ter processing. During 14 monthsof storage, β-carotene andlycopene showed an insignificantdownward trend. β-cryptoxanthindid not change significantly dur-ing the first 10 months, butshowed a small significant de-crease after 14 months. Theepoxy carotenoids auroxanthinand flavoxanthin were formedduring storage.

The apocarotenals that can bederived from β-carotene areshown in Figure 5. Formation ofapocarotenals can occur sequ-entially or at random. The isola-tion of β-apo-8’-carotenal, β-apo-10’-carotenal and β-apo-12’-carotenal, along with β-cyclocitraland acetaldehyde, in a modelsystem suggests sequentialcleavage (19). Apocarotenals arerarely detected in foods, indicat-ing a fast turn-over.

Factors influencingcarotenoid degrada-tionIn model systems, carotenoiddecomposition has been shownto depend on carotenoid struc-ture, nature of the system, avail-able oxygen, exposure to light,water content or activity, tem-perature, atmosphere, presenceof antioxidants, prooxidants, freeradical initiators and inhibitors,and sulphites (20). The situationis more complex in foods, con-sidering the complicated interplayof the factors mentioned above,along with the varied nature andcomposition of foods, processingtreatment, packaging and stor-age conditions, activity oflipoxygenase and other en-zymes, and coupled oxidationwith lipids.

Figure 4. Transformation of violaxanthin during processing and storage of foods.

HO

OH

O

O

HO

OH

O

O

Violaxanthin

Luteoxanthin

HO

OH

O

Auroxanthin

O


Ample evidence that carotenoidsin foods vary in their susceptibil-ity to degradation can be foundin the literature, although discrep-ancies in the trend followed byspecific carotenoids can benoted. The effects of light andtemperature have also been welldemonstrated.

Lutein decreased slightly butβ-carotene was stable duringfreezing of winter squash (21).Under frozen storage, lutein wasstable while β-carotene de-creased 32% after three months.No loss of carotenoids was ob-served on freeze-drying. Duringstorage of freeze-dried squash at30ºC, loss of β-carotene reached15, 20 and 53% after one, twoand three months, respectively.However, after 3 months of stor-age at 3ºC, reduction of β-caro-tene was only 10%.

In acidified, pasteurised carrotjuice stored for three months, re-duction of lutein, α-carotene andβ-carotene concentrations in-creased with increasing storagetemperature and was alsogreater under illumination thanunder dark storage (22). The for-mation of 13-cis-isomers ap-peared to be favoured underlighted storage and the 9-cis-iso-mers in the dark.

In vegetable juice containingmainly tomato and carrot juice,after four days of exposure to 230ft-c of light at 4ºC, only 25% ofthe initial α- and β-carotene re-mained, while 75% of lycopenewas still present (23). Caroteneloss was extensive after eightdays. The control samples (heldin darkness) showed no or negli-gible destruction of carotenoids.β-carotene was also found to be

more sensitive than lycopeneduring heat-based processing oftomato (hot-break extract andtomato paste) (24).

The relative stability of lycopeneobserved above is unexpected,considering that lycopene de-grades rapidly in oil and low-moisture model systems (25, 26).In fact, because of this instabil-ity, loss of lycopene during analy-sis is considered a major analyti-cal problem (27-30).

The lycopene content in tomatopulp was found to decrease dur-ing heating under different pro-cessing conditions (31). The ap-parent rate constant forlycopene degradation increasedwith increase in the concentra-tions of lycopene, acids, sugarsand total solids. After fourmonths of storage, lycopene

Figure 5. β-Apocarotenals derived from β-carotene.

O

O

O

β-apo-8'-carotenal

β-apo-10'-carotenal

β-apo-12'-carotenal


loss was greater in freeze-driedfibre-rich tomato pulp than inoven-dried samples. Lycopenedegradation increased with ex-posure to air, light and high stor-age temperature.

After six weeks of light exposureat room temperature or storageat 6ºC in the dark, 60–70% of all-trans-lycopene of total lycopenewas retained in two commerciallyproduced spray-dried tomatopowders (32). Thus, light and in-crease of storage temperaturefrom 6ºC to room temperaturewere not important factors in thestability of lycopene in these pow-ders. At 45ºC, however, only 40%retention was observed after 6weeks.

Influence ofprocessing onbioavailabilityIt is recommended that strategiesto increase the dietary intake ofcarotenoid-containing foods in-clude measures to enhancebioavailability (33). For a longtime the major concern aboutprocessing in relation tocarotenoids had been preventinglosses. In recent years, attentionhas shifted to the effect ofprocessing on the bioavailabilityof carotenoids.

Cis-isomers have long been at-tributed lower vitamin A activitythan the trans-provitamin Acarotenoids. In recent years,trans-β-carotene was found to bepreferentially absorbed over 9-cis-β-carotene in humans (34-36)and ferrets (37). On the otherhand, cis-lycopene was observedto be more bioavailable thantrans-lycopene in ferrets (38).

Aside from geometrical isomeri-sation, processing has anothereffect on bioavailability. Carot-enoids in nature are protected bythe cellular structure, the destruc-tion of which renders the carot-enoids vulnerable to degradationas discussed above. On the otherhand, this natural protection lim-its the bioavailability. Processingdenatures proteins and breaksdown the cell walls, making therelease of carotenoids from thefood matrix easier.

Indeed, enzymatic disruption ofthe matrix enhanced thebioavailability of β-carotene fromwhole-leaf and minced spinachthe serum total β-carotene re-sponse over a 3-week period inhuman subjects (n=10 for con-trol group; n=12 per spinachgroup) was significantly differentbetween the whole leaf and theenzymatically liquefied spinachgroups, and between the mincedand the liquefied spinach groups(39). The lutein response, how-ever, did not differ among thespinach groups. In another studyinvolving eight healthy females,daily consumption of processedcarrots and spinach over a 4-week period resulted in an in-crease in plasma β-carotene con-centration, averaging three timesthat associated with the ingestionof the same amount of β-caro-tene in the raw vegetables (40).

Determining the carotenoid in thechylomicrons of five subjectsgiven a single dose of fresh to-mato or tomato paste, ingestedtogether with corn oil, consump-tion of tomato paste resulted in2.5-fold higher total and all-trans-lycopene peak concentrationsand 3.5-fold higher total area un-der the curve than consumptionof fresh tomato (41). In an earlier

study, ingestion of heat-pro-cessed tomato juice (cooked inan oil medium) resulted in a 2- or3-fold increase in lycopene se-rum concentrations one day af-ter ingestion (42). An equivalentconsumption of unprocessed to-mato juice caused no rise inplasma concentrations. Caroten-oid response in triglyceride-richlipoproteins after single con-sumption (n=11) and plasmacarotenoid concentrations afterfour days of daily consumption(n=33) showed that matrix dis-ruption of canned peeled, wholetomatoes by mechanical homog-enisation and/or heat treatmentenhanced carotenoid bio-availability (43).

Current knowledge thereforesuggests that processing condi-tions should be optimised to pre-vent appreciable losses ofcarotenoids while enhancingtheir bioavailability.

SummaryThe major reactions undergoneby the highly unsaturatedcarotenoids during processingand storage of foods are geo-metrical isomerisation and oxida-tion. Isomerisation of trans-carotenoids to cis-carotenoids,promoted by contact with acids,heat treatment and exposure tolight, diminishes the colour andalters the biological activity. Themajor cause of carotenoid loss,however, is enzymatic and non-enzymatic oxidation, which de-pends on the availability of oxy-gen and the carotenoid structure.It is stimulated by light, heat,metals, enzymes and peroxidesand is inhibited by antioxidants.Data on percentage losses ofcarotenoids during food process-ing and storage are somewhat


conflicting, but carotenoid degra-dation is known to increase withthe destruction of the food cellu-lar structure, increase of surfacearea or porosity, length and se-verity of the processing condi-tions, storage time and tempera-ture, exposure to light, permeabil-ity to O2 of the packaging. Con-trary to lipid oxidation, for whichthe mechanism is well estab-lished, the oxidation of carot-enoids is not well understood. Itinvolves initially epoxidation andcleavage to apocarotenoids.Subsequent fragmentations re-sult in a series of compounds oflow molecular masses. Com-pletely losing their colour and bio-logical activities, the carotenoidsgive rise to volatile compoundswhich contribute to the aroma/fla-vour, desirable in tea and wineand undesirable in dehydratedcarrot. Processing also influencethe bioavailability of carotenoids,through geometrical isomerisa-tion and disruption of the cellularstructure.

AcknowledgmentThe author acknowledges withgratitude the financial supportgiven by MCT-FINEP-CNPqthrough the project PRONEX No

4196091500.

References1. Rodriguez-Amaya DB. Carotenoids

and food preparation: The retentionof provitamin A carotenoids in pre-pared, processed, and stored foods.Arlington: Opportunities for Micronu-trient Intervention (OMNI), 1997

2. Lessin WJ, Catigani GL, SchwartzSJ. Quantification of cis-trans iso-mers of provitamin A carotenoids infresh and processed fruits and veg-etables. J Agric Food Chem 1997,45: 3728-3732

3. Panalaks T, Murray TK. The effect of

processing on the content of caro-tene isomers in vegetables andpeaches. Can Inst Food Sci TechnolJ 1970, 3: 145-151

4. Sweeney JP, Marsh AC. Effect ofprocessing on provitamin A in veg-etables. J Am Diet Assoc 1971, 59:238-243

5. Chandler LA, Schwartz SJ. Isomeri-zation and losses of trans-β-carotenein sweet potatoes as affected byprocessing treatments. J Agric FoodChem 1988, 36: 129-133

6. Chen BH, Peng HY, Chen HE.Changes of carotenoids, color, andvitamin A contents during process-ing of carrot juice. J Agric Food Chem1995, 43: 1912-1918

7. Trujillo-Quijano JA, Rodriguez-Amaya DB, Esteves W, Plonis GF.Carotenoid composition and vitaminA values of oils from four Brazilianpalm fruits. Fat Sci Technol 1990, 92:222-226

8. Godoy HT, Rodriguez-Amaya DB.Occurrence of cis- isomers ofprovitamins A in Brazilian vegetables.J Agric Food Chem 1998, 46: 3081-3086

9. Nguyen ML, Schwartz SJ. Lycopenestability during food processing. ProcSoc Exp Biol Med 1998, 218: 101-105

10. Howard LR, Dewi T. Minimalprocessing and edible coating effectson composition and sensory qualityof mini-peeled carrots. J Food Sci1996, 61: 643-645, 651

11. Howard LR, Hernandez-Brenes C.Antioxidant content and market qual-ity of jalapeño pepper rings as af-fected by minimal processing andmodified atmosphere packaging. JFood Qual 1998, 21: 317-327

12. Hess CH, Rodriguez-Amaya DB. Ef-fect of minimal processing, maturityand season on the principalcarotenoids of leafy vegetables. JAgric Food Chem 2002 (submitted)

13. Cavalcante ML, Rodriguez-AmayaDB. Alteração da composição decarotenóides durante fabricação eestocagem da polpa de pitangaEugenia uniflora. Cienc Tecnol Ali-ment 2002 (submitted)

14. Oruña-Concha MJ, González-CastroMJ, López-Hernández J, Simal-Lazano J. Effects of freezing on thepigment content in green beans and

padrón peppers. Z Lebensm UntersForsch 1997, 205: 148-152

15. Cano MP, de Ancos B, Lobo G,Monreal M. Effects of freezing andcanning of papaya slices on theircarotenoid composition. Z LebensmUnters Forsch 1996, 202: 279-284

16. Godoy HT, Rodriguez-Amaya DB.Changes in individual carotenoids onprocessing and storage of mango(Mangifera indica) slices and purée.Int J Food Sci Technol 1987, 22: 451-460

17. Mercadante AZ, Rodriguez-AmayaDB. Effects of ripening, cultivar dif-ferences, and processing on thecarotenoid composition of mango. JAgric Food Chem 1998, 46: 128-130

18. Godoy HT, Rodríguez-Amaya DB.Comportamento dos carotenóidesde purê de mamão (Carica papaya)sob processamento e estocagem.Cienc Tecnol Aliment 1991, 11: 210-220

19. Padula M, Rodriguez-Amaya DB.Degradation of β-carotene in a low-moisture model system at 30ºC. For-mation of non-volatile and volatileproducts. J Agric Food Chem (sub-mitted)

20. Rodriguez-Amaya DB. Stability ofcarotenoids during storage of foods.In: Charalambous G, editor. Shelf-lifestudies of foods and beverages.Chemical, biological, physical andnutritional aspects. Amsterdam:Elsevier Science Publishers, 1993:591-628

21. Kon M, Shimba R. Changes in car-otenoid composition during prepara-tion and storage of frozen and freeze-dried squash. Nippon ShokuhinKogyo Gakkaishi 1989, 36: 619-624

22. Chen HE, Peng HY, Chen BH. Sta-bility of carotenoids and vitamin Aduring storage of carrot juice. FoodChem 1996, 57: 497-503

23. Pesek CA, Warthesen JJ. Photo-degradation of carotenoids in a veg-etable juice system J Food Sci 1987,52: 744-746

24. Abushita AA, Daood HG, Biacs PA.Change in carotenoids and antioxi-dant vitamins in tomato as a func-tion of varietal and technological fac-tors. J Agric Food Chem 2000, 48:2075-2081

25. Henry LK, Catignani GL, SchwartzSJ. Oxidative degradation kinetics of


lycopene, lutein, and 9-cis and all-trans-β-carotene. J Am Oil Chem Soc1998, 75: 823-829

26. Ferreira JEM. Cinética e fatores queinfluenciam na degradação decarotenóides em sistemas modelose alimentos. Master´s thesis.Universidade Estadual de Cam-pinas, Campinas, Brasil

27. Hart DJ, Scott KJ. Development andevaluation of an HPLC method forthe analysis of carotenoids in foods,and the measurement of the carot-enoid content of vegetables and fruitscommonly consumed in the UK.Food Chem 1995, 54: 101-111

28. Scott KJ, Finglass PM, Seale R, HartDJ, Froidmont-Görtz I. Interlab-oratory studies of HPLC proceduresfor the analysis of carotenoids infoods. Food Chem 1996, 57: 85-90

29. Riso P, Porrini M. Determination ofcarotenoids in vegetable foods andplasma. Int J Vitam Nutr Res 1997,67: 47-54

30. Konings EJM, Roomans HHS.Evaluation and validation of an LCmethod for the analysis ofcarotenoids in vegetables and fruit.Food Chem 1997, 59: 599-603

31. Sharma SK, Maguer ML. Kinetics oflycopene degradation in tomato pulpsolids under different processing andstorage conditions. Food Res Int1996, 29: 309-315

32. Anguelova T, Warthesen J. Lycopenestability in tomato powders. J FoodSci 2000, 65: 67-70

33. Olson JA, Parker RS, Reddy V,Rodriguez-Amaya DB, Smitasiri S,Tsou SCS. The bioavailability of di-etary carotanoids. Current concepts.A report of the International VitaminA Consultative Group (IVACG).Washington DC, 1999

34. Gaziano JM, Johnson EJ, RussellRM, Manson JE, Stampfer MJ,Ridker PM, Frei B, Hennekens CH,Krinsky NI. Discrimination in absorp-tion or transport of β-carotene iso-mers after oral supplementation witheither all-trans - or 9-cis -β-carotene.Am J Clin Nutr 1995, 61: 1248-1252

35. Stahl W, Schwarz W, von Laar J, SiesH. All-trans-β-carotene preferentiallyaccumulates in human chylomicronsand very low density lipoproteinscompared with 9-cis geometrical iso-mer. J Nutr 1995, 125: 2128-2133

36. Ben-Amotz A, Levy Y. Bioavailabilityof a natural isomer mixture comparedto synthetic all-trans-β-carotene inhuman serum. Am J Clin Nutr 1996,3: 729-734

37. Erdman JW, Thatcher AJ, HofmannNE, Lederman JD, Block SS, LeeCM, Mokady S. All-trans β-caroteneis absorbed preferentially to 9-cis-β-carotene, but the latter accumulatesin the tissues of domestic ferrets(Mustela putorius puro). J Nutr 1998,128: 2009-2013

38. Boileau AC, Merchen NR, WassonK, Atkinson CA, Erdman JW Jr. Cis-lycopene is more bioavailable thantrans-lycopene in vitro and in vivo in

lymph-cannulated ferrets. J Nutr1999, 129: 1176-1181

39. Castenmiller JJM, West CE, LinssenJPH, van het Hof KH, Voragen AGJ.The food matrix of spinach is a limit-ing factor in determining thebioavailability of β-carotene and to alesser extent of lutein in humans. JNutr 1999, 129: 349-355

40. Rock CL, Lovalvo JL, Emenhiser C,Ruffin MT, Flatt SW, Schwartz SJ.Bioavailability of β-carotene is lowerin raw rather than in processed car-rots and spinach in women. J Nutr1998, 128: 913-916

41. Gärtner C, Stahl W, Sies H.Lycopene is more bioavailable fromtomato paste than from fresh toma-toes. Am J Clin Nutr 1997, 66: 116-122

42. Stahl W, Sies H. Uptake of lycopeneand its geometrical isomers is greaterfrom heat-processed than fromunprocessed tomato juice. J Nutr1992, 122: 2161-2166

43. van het Hof KH, de Boer BCJ,Tijburg LBM, Lucius BRHM, Zijp I,West CE, Hautvast GAJ, West-strate JA. Carotenoid bioavail-ability in humans from tomatoesprocessed in different ways deter-mined from the carotenoid re-sponse in the triglyceride-rich lipo-protein fraction of plasma after a sin-gle conusumption and in plasma af-ter four days of consumption. J Nutr2000, 130: 1189-1196


Using immunisation contactsto deliver vitamin ATracey Goodman, EPI Team, Department of Vaccines and Biologicals,World Health Organization, Geneva, Switzerland

StatusChildren’s Summit Goal: Toachieve the sustainable elimina-tion of vitamin A deficiency by2010.• Globally, 136 countries have

a vitamin A deficiency (VAD)problem of public health sig-

nificance. 140–250 millionchildren under 5 years are atrisk.

• Issue of child survival, notjust blindness; delivery ofvitamin A supplements shownto reduce all cause mortalityby 23%, and reduce measlesand diarrhea morbidity.

• In 2000, 61 countries in-cluded vitamin A with polio ormeasles national immunisationdays (NIDs).

• 49 countries distributedvitamin A with routine immuni-sation contacts.

• 34 of these countries usedboth strategies.


Key issues• While much success has been

achieved linking vitamin A de-livery with NIDs the use of rou-tine immunisation contacts hasnot yet been fully realised.

• For sustainability, integration ofvitamin A with routine immuni-sation services (that is, post-partum maternal doses ofvitamin A given with first immu-nisation contact, and vitamin Agiven to children with measlesimmunisation at 9 months) isneeded.

Challenges1) Advocacy to increase imple-mentation: Need to seize op-portunities to promote vitamin A

as part of the global effort tostrengthen routine immunisationsystems.

2) Monitoring and reporting:Of the 49 countries distributingvitamin A with routine immunisa-tion contacts, only 21 countriesprovided vitamin A coverage onthe WHO/UNICEF Joint Report-ing Form for the year 2000, andonly 10 had coverage above80%. This points to difficulties inimplementation and monitoringwhich partners (particularly WHOand UNICEF) need to addressthrough strong technical support.

3) Collaboration with nationalnutrition programs: Successfulimplementation depends on goodcollaboration between national

immunsation and nutrition pro-grams. High-level Ministry ofHealth support is needed to en-sure the active engagement of alldepartments and the develop-ment of a national plan for theelimination of vitamin A deficiency.

Looking to thefuture:

• Increasing immunisation-linked opportunities to delivervitamin A: In April 2002, WH0-coordinated research trialscommenced in Tanzania andGhana to evaluate the ex-panded delivery of vitamin Awith DTP 1, 2 and 3 contacts.(results expected in December2003).


Enriching breast milk with vitamin APhilip Harvey, Nutrition Advisor, MOST, The USAID Micronutrient Program, and Re-search Associate, Bloomberg School of Public Health, Johns Hopkins University

Vitamin A and childsurvival

Three meta-analyses of largefield trials published almost adecade ago provided the ratio-nale for public health interven-tions that increase vitamin A in-take as strategies to reduce childmortality. Beaton et al. (1993)presented the best known ofthese and determined that im-proving vitamin A status reducedmortality in children aged 6–59months by an average of 23%.

Two other important findings fromthis work are less well known.First, the mortality reduction re-sulted from improved vitamin Aintake, not just from high-dosecapsules – in fact the interven-tion with the greatest mortalityreduction (54%) was low-doseweekly supplementation. Anotherfield trial was based upon MSGfortification. Second, the mortal-ity reduction was independent ofage, that is the 23% reductionwas constant across all agesfrom 6–59 months. Because mor-tality rates are higher in youngchildren than in older ones, theconstant 23% reduction meansthat more lives are saved inyounger children. In the eight fieldtrials analysed by Beaton et al.70% of the lives saved were inchildren 6–24 months old (seeTable I). The implication of thisfinding is that vitamin A interven-tions will have greater impact in

terms of number of lives savedby focusing on younger children.

Vitamin A in breastmilk

Since vitamin A is so importantto child survival, it is surprisingthat children, even in rich coun-tries, are born with virtually nostores of the vitamin. Thus breastmilk, as the infant’s first and ide-ally only food, is absolutely criti-cal to vitamin A nutrition. Havinghigher vitamin A concentration

than almost all complementaryfoods, breast milk remains theprimary source of the vitaminthrough the first twelve months,and in many countries remains amajor source throughout the sec-ond year of life. An infant’s intakeof vitamin A from breast milk isdetermined by the concentrationof vitamin A in the milk and by thevolume consumed.

The concentration of vitamin A incolostrum is particularly high butthis decreases rapidly over thefirst two or three weeks of lacta-

Breastfeeding mother from Mali.


tion. It is not widely recognisedthat the vitamin A concentrationof mature human milk is depend-ent upon the mother’s vitamin Astatus and her current intake ofthe vitamin. The concentration ofvitamin A in mature human milkin developing countries is onlyabout half that in developedcountries (Newman, 1994). Inareas where vitamin A intake islow and deficiency is common,breast milk will not necessarilyprovide sufficient vitamin A tomeet the needs of the infant,even when the breast-feedingpractices of the mother are ideal.Reviewing the importance ofmaternal vitamin A status foryoung children, Underwood(1994) concluded that subclinicalvitamin A deficiency problemswere becoming manifest from sixmonths of age forward, evenamong breast-fed infants, be-cause lactating women had inad-equate vitamin A status. Thebreast milk may have providedenough vitamin A for immediatefunctional requirements of theinfant including growth, but notenough to build any stores. Build-ing a store of the vitamin by sixmonths is a key protection for the

infant against infections such asmeasles and diarrhoea that de-plete vitamin A at a time whenintakes of the vitamin may de-crease.

The volume of breast milk con-sumed by the infant is deter-mined by the breast-feedingpractices of the mother. Exclu-sive, frequent breast-feeding forsix months will result in the great-est consumption of milk andshould be encouraged. In addi-tion to increasing intake of vita-min A, increasing breast milk con-sumption enhances protectionagainst illness by providing im-mune factors and a hygienicsource of nutrition. Reducing theincidence of infections improvesvitamin A status because infec-tions, in addition to causing lossesof vitamin A, decrease food intake,and also interfere with vitamin Aabsorption (Linkages: Facts forFeeding, Breastfeeding and Vita-min A, 20001).

Table I. Impact of age and mortality rate on vitamin A effect expressedas lives saved per 1000 children covered (data from Beaton et al.,1993)

Age (months) Mortality Lives saved/rate/1000 1000 covered

6–11 27.8 6.2

12–23 25.0 5.8

24–35 12.0 2.8

36–47 4.8 1.1

48–59 4.1 0.9

Baseline

0 – 2 months

3 – 4 months

5 – 6 months

May '76 Nov. '76

Survey period

May '77 Nov. '77

Pe

rc

en

t b

re

as

t m

ilk

sa

mp

les

> 3

0µ

g r

eti

no

l/d

l

100

80

60

40

20

Figure 1: Prevalence of adequate breast milk vitamin A, by period of lacta-tion, Guatemala Sugar Fortification, (adapted from Arroyave et al., 1979).


Effective strategiesfor enriching breastmilk with vitamin Aare available

Three options for enrichingbreast milk are available: post-partum dosing, fortification, andincreasing diet diversity. At thistime, the evidence of effective-ness for the first two of these isstronger than that for the third.

a) Postpartum dosing

Postpartum dosing increasesbreast milk vitamin A primarily byimproving the vitamin A status ofthe mother. It is a critical compo-nent of a comprehensive vitaminA strategy that often does not re-ceive the focussed effort neededto achieve adequate coverage.Combined with appropriatebreast-feeding practices it willensure that breast milk providesadequate vitamin A to both meetthe immediate needs of infantsand establish the stores neededto support survival in the crucialsecond six months of life (MOSTFAQ 42). Placebo-controlledstudies of the impact on breastmilk retinol by single postpartumdoses of 200,000 IU to 300,000IU have been conducted in Bang-ladesh, India, Indonesia, andThailand. Larger and longer last-ing improvements in milk vitaminA content and vitamin A status ofinfants were observed whenhigher doses were used. The lackof impact on vitamin A status ofinfants reported from some stud-ies using 200,000 IU has beenattributed to the dose being in-

adequate. Soon to be releasedIVACG guidelines will recom-mend doubling the current post-partum dose to 400,000 IU (twodoses of 200,000 IU at least oneday apart) delivered as soon af-ter delivery as possible, but notmore than six weeks after deliv-ery (see SIGHT AND LIFE News-letter 1/2001, pages 20–23).

b) Fortification

Consumption of foods fortifiedwith vitamin A increases breastmilk retinol both by increasingevery day intake of the vitaminand by improving status. The ef-ficacy of increasing breast milkvitamin A through fortification of

sugar was demonstrated in acontrolled study in El Salvador byArroyave et al. (1974). The effec-tiveness of this approach wasdemonstrated subsequentlythrough an INCAP study evalu-ating the impact of the nationalsugar fortification program in ru-ral Guatemala (Arroyave et al.,1979). Figure 1 shows the dra-matic impact fortification had onbreast milk vitamin A. In severalstudies authors have observedvitamin A concentrations in milkdecreasing with duration ofbreast-feeding and this has beeninterpreted as the vitamin being“drained” from maternal stores.By presenting the vitamin A lev-els in milk by period of lactation,Arroyave et al. identified that thegreatest impact was in motherswho had been lactating for 5–6months, the group that had the

1 Available at the Linkages web site at www.linkagesproject.org2 See Frequently Asked Questions on the MOST Project website at

www.mostproject.org

Prolonged breastfeeding.


lowest vitamin A levels at base-line. The INCAP evaluation alsodocumented increased concen-trations of serum retinol amongpreschool children resulting fromthis national fortification program(Arroyave et al., 1981). In a studyin Indonesia, MSG was fortifiedwith vitamin A and marketedthrough ordinary channels in five“program” villages. Five nearbyvillages served as controls. After12 months of intervention, serumand breast milk levels of vitaminA had increased dramatically inthe program villages but did notchange in the control villages(Muhilal et al., 1988).

c) Increasing diet diversity

Interventions that increase dietdiversity are appealing becausethey will improve overall food se-curity and the intake of many, notsingle, micronutrients. However,the evidence of their effective-ness, or even efficacy, is notstrong. A recent compilation ofexperiences by Helen Keller In-ternational/Asia-Pacific (2001)highlighted the broader benefitsof promoting homestead foodproduction including income gen-eration and nutritional benefits forwomen. Homestead food produc-tion in Bangladesh was shown toincrease intakes of vitamin A inboth women and children, but“harder” biochemical evidence ofeffectiveness is not yet available.Ruel and Levin (2000) reviewedthe literature on the impact offood-based strategies on vitaminA deficiency but reported beingunable to find data with sufficient

scientific rigor to allow firm con-clusions to be drawn about effec-tiveness. The lack of strong evi-dence that these strategies mightreduce vitamin A deficiency doesnot necessarily mean that the in-terventions have no impact, butrather that these impacts are ex-tremely difficult to measure. Re-cent small studies in Tanzania(Lietz et al., 2000) and Hondu-ras (Canfield et al., 2001) havedemonstrated the potential ben-efits for vitamin A status of sup-plementing pregnant and lactat-ing women with red palm oil. Diet-based strategies hold enormouspotential for broadly-based ben-efits and warrant further invest-ments for their development andrigorous evaluation.

ConclusionEnriching breast milk with vitaminA and promoting exclusivebreast-feeding for the first sixmonths are critically importantcomponents of any integrated in-tervention to reduce mortality re-sulting from vitamin A deficiencyduring the period when mortalityrates are very high.

ReferencesArroyave G, Beghin I, Flores M et al.Efectos del consumo de azúcarfortificado con retinol, por la madreembarazada y lactante cuya dieta ha-bitual es baja en vitamina A. ArchLatinoam Nutr 1974, 24: 485-512

Arroyave G, Aguilar JR, Flores M et al.Evaluation of sugar fortification with vi-tamin A at the national level. Institute ofNutrit ion of Central America andPanama – Pan American Health Or-ganization (PAHO), 1979, ScientificPublication No. 384

Arroyave G, Mejia LA, Aguilar JR. Theeffect of vitamin A fortification of sugaron the serum vitamin A levels of pre-school Guatemalan children: a longitu-dinal evaluation. Am J Clin Nutr 1981,34: 41-49

Beaton GH, Martorell R, Aronson KJ etal. Effectiveness of vitamin A supple-mentation in the control of young childmorbidity and mortality in developingcountries. ACC/SCN State-of-the-ArtSeries Nutrition Policy Discussion Pa-per No. 13. UNCC/SCN, New York,1993

Canfield LM, Kaminsky RG, Taren DLet al. Red palm oil in the maternal dietincreases provitamin A carotenoids inbreast milk and serum of the mother-infant dyad. Europ J Nutr 2001, 40; 1:30-38

Helen Keller International/Asia-Pacific.Homestead Food Production – A strat-egy to combat malnutrition and poverty.Helen Keller International, Jakarta, In-donesia, 2001

Lietz G, Henry CKJ, Mulokozi J et al.Use of red palm oil for the promotion ofmaternal vitamin A status. Food NutrBull 2000, 21; 2: 215-218

Muhilal, Murdiana A, Azis I et al. Vita-min A fortified monosodium glutamateand vitamin A status: a controlled fieldtrial. Am J Clin Nutr 1988, 48: 1265-1270

Newman V. Vitamin A and breast-feed-ing: a comparison of data from devel-oped and developing countries. FoodNutr Bull 1994, 15

Newman V. Vitamin A and Breastfeeding:A comparison of data from developedand developing countries. San Diego,Wellstart International, 1993

Ruel MT, Levin CE. Assessing the po-tential for food-based strategies to re-duce vitamin A and iron deficiencies: areview of recent literature. InternationalFood Policy and Research Institute,2000, SFCND Discussion Paper No. 92

Underwood BA. Maternal vitamin A sta-tus and its importance in infancy andearly childhood. Am J Clin Nutr 1994,59 (suppl): 517S-524S

www.sightandlife.org


Vitamin A, growth faltering in infancyand gut integrityDr Christine Northrop-Clewes, Northern Ireland Centre for Food and Health,University of Ulster, Coleraine, Northern Ireland, UK

SummaryIt is well established that vitaminA is needed for epithelial differ-entiation, the production of gob-let cells and the maintenance ofan effective epithelial barrieragainst pathogenic attack. Stud-ies from The Gambia now sug-gest that failure to maintain theintegrity of the epithelia in the gutis closely linked to the widely ob-served problem of growth falter-ing. The events leading to thisdiscovery are outlined in thisshort review.

Growth faltering is a commonproblem in socially deprived ar-eas of the world and may becaused by a combination of fac-tors. Infection has been impli-cated and diarrhoea is often oneof the first signs. If diarrhoea isaccompanied by mucosal dam-age then catch-up growth follow-ing an episode cannot occur un-til the injury is repaired.

We studied the gut integrity of120 Gambian infants using thedual sugar permeability test. In-fants were recruited at 2 monthsof age and followed for the next13 months. Gut integrity wasmeasured monthly and we foundthe integrity of the mucosa pro-gressively deteriorated followingthe introduction of weaning food.Seasonally, the data showed thatintegrity was least impaired from

April to June, coinciding with thetime of maximum vitamin A (VA)intake – the mango season. Theresults suggest that VA status mayinfluence gut integrity during thevulnerable weaning period.

Growth falteringGrowth faltering is a commonproblem in many developingcountries and in socially deprivedareas throughout the world. Datafrom The Gambia illustrates fac-ets of the problem which arecommon to many countries. In-fants are born with a mean ex-pected weight-for-age of approxi-mately 93%, which improves dur-

ing the first 3 months of life. How-ever, between 3 to 6 months aprecipitous fall in mean expectedweight- and length-for-age oc-curs, which stabilises at about75% of expected values when theinfants are12 to15 months of age(Figure 1) (1). The precipitous fallin weight and length gain, knownas growth faltering, is associatedwith the introduction of compli-mentary weaning foods andclosely linked to worsening gutintegrity. The process appears tobe complex, and causes sug-gested have included disease,feeding patterns, specific nutrientdeficiencies, growth factors and/or psycho-social conditions.

95

90

85

80

75

70

0 6 12 18

Age (months)

% e

xp

ec

ted

we

igh

t-fo

r-a

ge

24 30 36

100

Figure 1: Growth performance of Gambian infants expressed as percent ofexpected weight-for-age according to NCHS standards.


Infection andgrowth faltering

Infections and infestations havebeen implicated as some of themain causes of growth faltering.In overcrowded, unhygienic ordeprived environments, both indeveloped and developing coun-tries, even trivial acute infectionsfollowing in quick successionmay not allow children sufficienttime for catch-up growth betweenepisodes of disease. In develop-ing countries, conditions such asmalaria, diarrhoea, respiratoryinfections, Helicobacter pyloriand rotavirus are commonly as-sociated with growth faltering.

Diarrhoea, in particular, is oftenone of the first signs of the onsetof growth faltering and usuallyoccurs shortly after weaningfoods are introduced. Episodesof diarrhoea cause short-termgrowth faltering in both weightand height and the ability of chil-dren to catch-up with their ex-pected growth trajectory aftersuch episodes can vary depend-ing on the cause of the diarrhoea.

It is important that diarrhoea beregarded as a symptom not a dis-ease. The pathophysiology of di-arrhoea differs according to the“cause”, hence the impact of theillness on weight and heightgrowth and the extent of mucosaldamage will also vary. Episodesassociated with a systemic in-flammatory reaction can result insevere growth faltering during theacute phase of the illness but inthe absence of mucosal injury,catch-up growth could be rapid.If the diarrhoea is accompaniedby mucosal damage then fullcatch-up might not be expecteduntil the injury is repaired.

Measuring mucosaldamage using thedual sugar perme-ability test

Little is known about the timetaken for restoration of normalmucosal structure and functionfollowing injury because of diffi-culties of measurement. How-ever, non-invasive techniquesbased on the permeation ofpoorly absorbed, non-metabo-lised sugars are available meth-ods of assessing the integrity ofthe small intestine. Most of myown experience in this field hasbeen using two sugars, lactuloseand mannitol. The sugars perme-ate the mucosa by unmediateddiffusion and the rate is deter-mined by molecular size (cross-sectional diameter not weight) ofthe probes, lactulose is 9.5 Å insize and permeates more slowlythan mannitol (6.7 Å). The differ-ential excretion, following an oraldose of two sugars of differing

molecular size, can be used as ameasure of mucosal integrity.

Under normal circumstances, asa child grows, the surface areaof the gut increases, the amountof mannitol absorbed and ex-creted into urine increases andthe ratio of lactulose:mannitol(L/M) decreases. In industrialisedcountries, the L/M ratio of a nor-mal infant will fall from 0.12 to0.02 over the first 12 months oflife. In the presence of disease,however, bacteria attach to themucosal surface and alter cellpermeability. The villous structureof the gut becomes flattened andthe surface area decreases. Inthese circumstances, the amountof mannitol absorbed and ex-creted decreases and the L/Mratio increases.

Intestinal disease,growth and the dualsugar permeabilitytest in Gambian in-fantsTo explore the relation betweenintestinal disease and growthperformance, the dual sugar per-meability test was used in a pro-spective longitudinal study in TheGambia (2). Infants (n=120) wererecruited as they reached 2months and followed through thenext 13 months to 15 months ofage. Weight and length weremeasured monthly and morbid-ity was recorded weekly. Gut in-tegrity was measured using thedual sugar permeability test on amonthly basis. Briefly, the testinvolved giving a solution of 400mg of lactulose (disaccharide)and 100 mg of mannitol (mon-osaccharide) in 2 ml of water.Children received 2 ml per kg

Baby with urine bag.


body weight up to a maximumdose at 10 kg weight. Urine wascollected over the following 5hours using a urine bag. Urinarylactulose and mannitol weremeasured using enzymatic tech-niques and the L/M ratio was cal-culated as an expression of mu-cosal integrity.

Results showed that for the first3 months of life, growth was nor-mal as expected (Figure 1). Be-yond this, both weight and lengthdeteriorated and by 14 months ofage, mean length and weight Z-scores (±SD) were –2.13 (±0.88)and –2.03 (±0.99), respectively(i.e. approximately 75% of ex-pected values for reference chil-dren of the same age).

Intestinal permeability ratios werenormal and very close to thoseof infants of similar age in the UK(L/M=0.12) up to 3 months, butbeyond this age the L/M ratiorose progressively, peaking in the9–12 month age group (L/M=0.5). Intestinal permeability tolactulose did not change with in-creasing age suggesting that themain alteration in the L/M ratiowas due to a change in manni-tol. There was a marked declinein mannitol absorption from 3months of age onwards and thereduction in mannitol uptake in-dicated a decrease in mucosalabsorptive area as a result ofpartial villous atrophy. The resultsimply that a gradual deteriorationin small bowel mucosa took placethroughout the first year of lifeand this deterioration stronglycoincided with poor growth. Sta-tistically, the relationship can beexplained by age-corrected re-gression equations betweenchange in weight (kg/month) orlength growth (cm/month) andthe log of the permeability ratio

(approximately 1000 datapoints), which suggested that~40% of growth faltering in bothweight and length can be ex-plained by abnormal L/M ratios.The effect of diarrhoea on gut in-tegrity was short-term and notsignificant. Abnormal permeabil-ity ratios were measured in 700out of 922 tests (76%) but infantsonly had diarrhoea for 14% of thetime. When regression equationsbetween change in weight growth(kg/month) and percentage oftime with diarrhoea were calcu-lated, no significant relationshipwas found. Our data thereforeshowed no long-term relationshipbetween diarrhoeal disease andgrowth but that a high prevalenceof intestinal damage was a ma-jor determinant of poor growth.

Vitamin A and gutintegrity

VA is known to play a role in main-taining integrity of epithelial tis-sues such as the gut mucosa andin assisting in the body’s re-sponse to inflammatory stress. InThe Gambia, there is a markedseasonal fluctuation in the avail-ability of VA, as most VA is de-rived from β-carotene during themango season. Therefore, inview of the seasonality of VA in-take, the longitudinal data on gutintegrity and growth were re-ana-lysed (3).

Figure 2 shows a combined his-togram in which changes ingrowth rate (mean monthly

Dec

0.65

0.55

– 0.1

– 0.2

– 0.3

– 0.4

– 0.5

– 0.6

0

0.45

0.35

Feb Apr Jun

Month

L/M

(g

eo

me

tric

me

an

)

Z-S

co

re

in

cre

me

nt

Z-Score

L/M (age corrected)

Aug Oct Dec

0.25

Figure 2. Seasonal changes in weight Z-scores (top) and gut permeability(bottom) in Gambian infants. Each bar represents mean values for 50-60infants. Z-score bars are means of differences between respective monthlydata less values from previous month.


change in weight z-score) andgut integrity (L/M ratio) were plot-ted against month of the year.Intestinal permeability was foundto be least impaired from April toJune, the time of maximum VAintake. The poorest L/M ratioswere found during the rainy sea-son (July to September). Thedata therefore suggested that gutintegrity and growth can be ex-plained in terms of food availabil-ity (April to June) and diseaseprevalence during the rainy sea-son (July to October) (4).

During November the main har-vest occurs and food is plentifuluntil the end of May. The dry sea-son is from November to May andis the healthiest time for Gambianpeople, although respiratory dis-ease and rotavirus do occur dur-ing this time period. Rain fallsfrom June to October and coin-cides with the period of hardestwork in the fields and of the high-est prevalence of diarrhoea andmalaria. Figure 2 shows thegreatest weight loss and poorestgut integrity occurring betweenJune and September. Food isalso in short supply from June toSeptember and miscellaneousleaves may be used to makesauces to supplement the mainstaple. The leaves probably sup-ply some VA but by far the larg-est supply of VA is obtained dur-ing the mango season (April toJune), consequently the VA sup-ply of carotenoid-rich food is veryseasonal. In this context it is ofinterest to note that Quadro et al.working in Brazil infants found astrong inverse correlation be-tween serum vitamin A and urineL/M ratios (r=–0.46, p=0.12) anda highly positive correlation be-tween serum retinol and urinarymannitol (r=0.66, p<0.01) (7).The first results confirm our ob-

servations of better gut integrityin Gambian infants during themango season, and that poor VAstatus is associated with reducedmucosal surface area.

Additional data illustrating theclose link between infection andgut integrity was obtained frommeasuring an acute phase pro-tein, α-1-antichymotrypsin (ACT).Figure 3 shows that the preva-lence of sub-clinical infection wasat its lowest from April to Junecorresponding to the time of bestgut integrity, most rapid growthand also with the plentiful supplyof mangoes.

Role of vitamin A inmaintaining gut in-tegrityAlthough VA deficiency is notconsidered to be a clinical prob-lem in The Gambia, several stud-ies have shown large seasonalfluctuations in plasma retinol con-centrations and in the dietary in-take of VA (5, 6). Fluctuatingplasma values in Gambian in-fants indicate that VA status maynot always be adequate to pre-vent the deterioration in gut per-meability observed during wean-ing. However, we do not know

Girl with mango.

Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Month

An

tich

ym

otr

yp

sin

(g

/l)

1.2

1.0

0.8

0.6

0.4

Figure 3. Seasonal changes in α-1-antichymotrypsin.


what causes the initial loss of gutintegrity. Before the introductionof weaning foods, Gambian in-fants have normal gut integrityand growth is near to normal, butboth deteriorate subsequently.Very few cases of abnormal gutintegrity are found in Western in-fants, but bacterial contaminationof weaning foods is much lowerthan in The Gambia and nutri-tional status in Western infants isprobably better, hence both fac-tors are probably important indetermining gut sensitivity todamage. The introduction of lo-cally-produced weaning foods toan immature infant may thereforeinitiate tissue damage, perhapsdue to dietary antigens in combi-nation with bacterial contamina-tion leading to inflammation, in-creased bacterial translocationand an increased risk of systemicinfection.

Gambian infants are fed a formof cereal gruel made from milletor rice as a first weaning food.Food antigens like lectins, occurr-ing in common dietary staplessuch as cereal grains and leg-umes, can have potent anti-nutritional properties, influencingthe structure and function of bothenterocytes and lymphocytes.Lectins are glycoproteins whichcan bind to the surface glycanson gut brush border epithelialcells causing damage to the baseof the villi, disarrangement of thecytoskeleton, increasing endocy-tosis and shortening of the micro-villi resulting in abnormal perme-ability. Such damage to the mu-cosa may facilitate the passageof food antigens and pathogenicbacteria. Once damaged a newbout of infection or further expo-sure to dietary antigens wouldprevent repair and precipitate fur-ther damage.

Food availability during the dryseason probably stimulatesgrowth but the increase in dietaryVA may be particularly importantin reducing levels of infection asreflected by the ACT concentra-tions (Figure 3). The lowestmonthly mean ACT was in April,the height of the mango season,and the ACT values for April, Mayand June were not significantlydifferent. The L/M ratios mirroredthe ACT concentrations. Themechanism by which VA influ-ences infection is not clear. A di-rect effect of VA on immune cellsis possible but gut tissue isunique in being able to use nutri-ent from both the serosal and lu-minal side of the mucosa. It ispossible that dietary VA may actdirectly on the gut enterocytes torestore integrity thereby prevent-ing further bacterial translocationand increasing resistance to fur-ther infection.

ConclusionThe gut integrity of infants in de-veloping countries is often abnor-mal and this is closely linked tofailure to grow. We found bio-chemical measurements of gutintegrity were best at the time ofyear when dietary VA was mostabundant. However, the mecha-nism for this interaction is notknown. VA may have a direct ef-fect on gut cells or increased in-take may increase circulatingconcentrations of retinol, whichmay have systemic effects. Vita-min A is also known to be impor-tant for the proper functioning ofthe immune system. In infants theimmune system is immature, butundoubtedly developing rapidlyduring the first 12 months of life.Interaction between immune tis-sue, vitamin A and gut integrityhas yet to be fully described.

References

1. Lunn PG, Northrop-Clewes CA,Downes RM. Recent developmentsin the nutritional management of di-arrhoea 2. Chronic diarrhoea andmalnutrition in The Gambia: studieson intestinal permeability. Trans RSoc Trop Med Hyg 1991, 85: 8-11

2. Lunn PG, Northrop-Clewes CA,Downes RM. Intestinal permeability,mucosal injury and growth faltering inGambian infants. Lancet 1991, 338:907-10

3. Lunn PG, Northrop-Clewes CA,Downes RM. Seasonal fluctuations invitamin A status and health indicatorsin Gambian infants. Proc Nutr Soc1994, 53: 144A

4. Bates CJ, Prentice AM, Paul AA. Sea-sonal variations in vitamins A, C, ri-boflavin and folate intakes and sta-tus of pregnant and lactating womenin a rural Gambian community: somepossible implications. Europ J ClinNutr 1994, 48: 660-668

5. Nathanail L, Powers HJ. Vitamin Astatus of young Gambian children:biochemical evaluation and conjunc-tival impression cytology. Ann TropPaediatr 1992, 12: 67-73

6. Thurnham DI, Northrop-Clewes CA,McCullough FSW, Das BS, Lunn PG.Innate immunity, gut integrity and vi-tamin A in Gambian and Indian in-fants. J Infect Dis 2000, 182 (Suppl1) S23-28

7. Quadro L, Gamble MV, Vogel S, LimaAAM, Piantedosi R, Moore SR,Colantuoni V, Gottesman ME,Guerrant RL, Blaner WS. Retinol andretinol-binding protein: gut integrityand circulating immunoglobulins. JInfect Dis 2000, 182 (Suppl 1) S97-S102.


Many countries now have suc-cessful ongoing community-based vitamin A supplementationprograms. The increased empha-sis on these programs has beenfueled by the demonstration thatsuch programs can improve childsurvival in environments wherevitamin A deficiency is prevalent.However, the real challenge nowlies in how to sustain high sup-plement coverage over time incountries where fortification orpromotion of vitamin A-rich foodsthat can impact on status areunlikely to be appropriate strate-gies for many years to come.Community-based supplementdistributors can play an importantrole in motivating participation insupplementation programs, andin creating the demand for suchprograms within the community.What attributes and circum-stances make some distributorsmore successful than others inproducing high coverage for sup-plementation programs?

One study addressed this ques-tion using data about male vil-lage-based distributors and theircoverage rates within the bi-an-nual government supplementa-tion program in Aceh province,Indonesia, in 1983 (1). This studyfound that the most successfuldistributors were farmers withminimal education, and that

smaller villages further from themain roads and without anystores had higher coverage thatlarger, more urbanized villages.The study did not identify anycharacteristics of the programparticipants that resulted inhigher coverage.

Maternal supplementation withiron folate, vitamin A or othermicronutrients poses a differentset of coverage challenges sincedaily, or at least weekly supple-mentation is most appropriatefrom both a safety and efficacyperspective during pregnancy.

Identifying the characteristics ofa successful distributor is likelyeven more important for sustain-ing coverage with a more fre-quent dosing regimen than it isfor the twice yearly campaignstyle approach that supports achild survival impact (2). Wetried to answer the question ofwhat makes a successful ante-natal distributor in the context ofa community trial to examine theimpact of weekly maternal vita-min A or β-carotene supplemen-tation on maternal and infanthealth and survival in Sarlahidistrict, Nepal (3).

What makes a successfulsupplement distributor?Joanne Katz, Keith P. West Jr., Lee Wu, Subarna K. Khatry, Elizabeth K. Pradhan, ParulChristian, Steven C. LeClerq, Sharada Ram Shrestha.The Center for Human Nutrition and the Sight and Life Research Institute of the De-partment of International Health, the Johns Hopkins Bloomberg School of PublicHealth, Baltimore, Maryland, the Nepal Nutrition Intervention Project Sarlahi (NNIPS),and Nepal Netra Jyoti Sangh, Kathmandu, Nepal

Women involved in the study in Sarlahi, Nepal.


The Nepal Nutrition InterventionProject Sarlahi (NNIPS) is a se-ries of randomized communitytrials examining the role of differ-ent micronutrient supplements onhealth and survival of women andchildren in a rural subsistenceenvironment in South Asia. Thefirst trial examined the impact ofthrice yearly large-dose vitaminA supplementation on child sur-vival (2). The second of these tri-als involved weekly supplemen-tation of 45,000 women of child-bearing age and its impact onmaternal and infant survival (4),(5). The third and fourth trialsexamine the impact of daily sup-plements of other micronutrientsfor women and children, respec-tively.

To undertake weekly supplemen-tation in the second study, weidentified and trained a cadre ofover 400 local village-basedwomen distributors who would beresponsible for supplementing agroup of an average of 110

(range from 32 to 292) women intheir neighborhood. The distribu-tor visited each woman on her listweekly and gave the supplementdirectly to her. She then recordedwhether the supplement wastaken, whether the woman re-fused to take it, or whether nosupplement was given becauseshe was unable to find thewoman at home during thatweek. Distributors spent about 4

hours per week delivering sup-plements, and were paid a rela-tively small amount of monetarycompensation, the equivalent ofUSD 15-20 per month. The em-ployment was part-time and thetiming flexible, so as to allow thedistributors to fulfill their house-hold obligations, and to visit par-ticipants when they were mostlikely to be at home. In addition,the distributors met every Fridayto review their work, discussproblems and their solutions,hand in completed forms, receivenew forms, report pregnanciesand deliveries, and replenishsupplement stores. Supplemen-tation continued for three years,from 1994 through 1997.

All women who applied for the jobof supplement distributor wereinterviewed before any employ-ment decision was made. Demo-graphic and socio-economiccharacteristics were obtainedfrom each applicant. Character-istics of the neighborhood forwhich the distributor was respon-sible were identified by projectsupervisors prior to the start ofthe trial. The coverage level foreach distributor was defined asthe percentage of doses actually

Table I. Predictors of low and high weekly supplement coverage,Sarlahi, Nepal, 1994-1997

Low coverage High coverage< 50% > 70%

Weekly market present 18.2% 9.7%Literacy 98.2% 94.4%Low socio-economic status 27% 33%Age < 20 years 9.6% 12.7%Mean hrs/week housework 42.4 38.2Mean hrs/week distributing 5.5 4.5Mean no. women supplemented 114 101

One of the over 400 local village-based women responsible for supplemen-tation and collection of data in Sarlahi, Nepal.


consumed out of the total numberof possible doses for all womenon the distributor’s list over theduration of the trial. The cover-age ranged from 16% to 86%,with the average being 61% of allpossible doses actually con-sumed. High coverage was de-fined as 70% or more, and lowcoverage as less than 50% of allpossible doses consumed.

As shown in the Table I, distribu-tors with high coverage were lessliterate than those with low cov-erage (98% versus 94%).Women with high coverage re-ported spending one hour lessper week distributing supple-ments, but they also had an av-erage of 13 fewer women to sup-plement each week, compared tothose with low coverage. Dis-tributors with low coverage re-ported doing 5 more hours perweek of housework than thosewith higer coverage. Villages witha weekly market had lower cov-erage than those without such amarket. A measure of householdsocio-economic status that in-cluded ownership of land, cattle,ox-carts and type of housing wasnot found to be associated witheither low or high coverage, af-ter taking literacy, age, workloadand presence of a weekly mar-ket into account.

This study found strikingly simi-lar characteristics of predictedcoverage among village-basedmale distributors of twice yearlyvitamin A supplements in Indone-sia as among female distributorsof weekly supplements in Nepal.Those with lower levels of edu-cation had better performancethan those with more education,perhaps because they could in-teract more comfortably with theprogram participants, whoselevel of education was closer totheir own. Similarly, coveragewas lower in communities thathad a weekly market or had vil-lage stores, perhaps reflectingvillages where there were moredistractions for participants anddistributors alike. Work condi-tions were somewhat associatedwith low coverage in that thosewith more competing work de-mands at home had lower cov-erage rates. Those with low cov-erage also had more women tosupplement, and consequentlyreported spending more time dis-tributing supplements. A lowerworkload at home and on the jobdid not appear to predict highcoverage, but a higher workloaddid seem to have a negative im-pact on coverage.

There is increasing interest byUNICEF and others in daily ante-natal micronutrient supplementa-tion. Creative ways of designing,

implementing and sustainingsuch programs at the communitylevel will be needed if this type ofsupplementation can be shownto have a positive impact on ma-ternal and infant health. Studieslike this can be helpful in identi-fying the types of communityworkers who are most likely tobe successful program imple-menters.

References

1. Tarwotjo I, West KP, Mele L, et al.Determinants of community-basedcoverage: periodic vitamin A supple-mentation. Am J Public Health 1989,79: 847-849.

2. West KP, Pokhrel RP, Katz J, LeClerqSC et al. Efficacy of vitamin A in re-ducing preschool child mortality: arandomized double-masked commu-nity trial in Nepal. Lancet 1991, 338:67-71.

3. Katz J, West KP Jr, Wu L, Khatry SK,et al. Determinants of maternal vita-min A and β-carotene supplementa-tion coverage among village basedwomen distributors in Nepal. Am JPublic Health 2002, 92: 1105-1107.

4. West KP Jr, Katz J, Khatry SK, et al.Double-blind, cluster randomised trialof low dose supplementation with vi-tamin A or β-carotene on mortality re-lated to pregnancy in Nepal. BMJ1999, 318: 570-575.

5. Katz J, West KP Jr, Khatry SK, et al.Low-dose vitamin A or β-carotene sup-plementation does not reduce earlyinfant mortality: A double-masked,randomized, controlled communitytrial in Nepal. Am J Clin Nutr 2000,71: 1570-6.


Vitamin A program in India –why the controversy?Dr Vinodini Reddy, Former Director National Institute of Nutrition,Hyderabad 500 007 A.P, India

A Vitamin A supplementation pro-gram has been in operation inIndia since 1970. Under this pro-gramme, sponsored by the Min-istry of Health and Family Wel-fare (GOI), children aged be-tween 9 months to 3 years aregiven six monthly doses of vita-min A, and the administration ofthe first two doses is linked withroutine immunisation. Althoughthe supplementation programmewas initially started as a short-term measure to prevent blind-ness in children, it has been go-ing on for the last three decadesand its continuation has becomea subject of national debate. Therecent reports of child deaths af-ter the administration of vitaminA during a mass campaign inAssam triggered a fresh contro-versy over the vitamin A program(1–3). The controversy is notconfined to the campaign ap-proach for vitamin A distribution,but the very existence of vitaminA deficiency (VAD) as a publichealth problem in India and theneed for supplementation arequestioned (4). Such debates of-ten confuse the policy makersand cause a set-back to the on-going programme, which is al-ready suffering from tardy imple-mentation. An attempt is madehere to review the available dataand answer some of the ques-tions raised by the critics.

Is VAD a publichealth problem inIndia?Clinical deficiency: Severe defi-ciency of vitamin A is known toproduce corneal xeropthalmia/keratomalacia and blindness inchildren. Such cases are rarelyseen in a community survey andrequire a large sample size foraccurate estimates of prevalence.Hospital records show a signifi-cant decline in keratomalaciacases in the last two decades (5)and clinicians vouch for its rarity(6). However, clinical signs of mildxeropthalmia like Bitot’s spots andnight blindness are still seenamong children in deprived com-

munities. The first repeat surveyof the National Nutrition Monitor-ing Bureau (NNMB) conductedduring 1988–1990, in the samevillages as those surveyed earlierduring 1975–1979, showed thatthe prevalence of Bitot’s spots hasdeclined from 1.8% to 0.7% (7).But the second repeat survey con-ducted in 1996–1997 showed nofurther improvement (8) and theprevalence is still above 0.5%(Figure 1), the WHO cut-off levelfor a public health problem. Thenational averages do not give afull picture because the preva-lence rates vary widely, not onlybetween the states but also withina state. Nevertheless, they pro-vide useful information on timetrends.

2.0

1.6

1.2

0.8

0.4

0

1977 1990 1996

0.70.7

1.8

Year

%

Figure 1. Prevalence of Bitot’s spots in pre-school children.


India Nutrition Profile (1999) isoften quoted to show low preva-lence of clinical deficiency in thepopulation, but the prevalencerates of Bitot’s spots published inthis report cannot be used be-cause they are based on pooleddata of all age groups (9). In afew states like Haryana, Assamand Orissa, for which the data onpreschool children are givenseparately, the prevalence is rela-tively higher. A survey in fivenorth-eastern states (Assam,Bihar, Orissa, West Bengal andTripura) showed the prevalenceof Bitot’s spots to be 0.7–2.2%and that of night blindness 1.2–4.0%, indicating a public healthproblem in all the five states (10).The survey also showed highprevalence of night blindnessamong pregnant women (3.2–16%). The district-wise data col-lected in the state of UttarPradesh showed Bitot’s spots in5.6% of children (11). There wasa wide variation in the prevalencebetween the districts and evenwithin a district from cluster tocluster, ranging from 0.2% to13.7%. A recent survey of the In-dian Council of Medical Research(ICMR) (1998) covering 16 dis-tricts, mostly in northern andeastern regions, showed that theprevalence of Bitot’s spotsranged from 0–4.7% and that ofnight blindness from 0.4–4.8%(12). Low prevalence of Bitot’sspots observed in a number ofdistricts surveyed is used to ar-gue that VAD is no longer a pub-lic health problem, but the preva-lence of night blindness, thougha subjective sign, cannot be ig-nored. If both indicators are used,VAD is a significant problem in 7districts and if the prevalence ofcorneal scars (>0.05%) is alsoconsidered, 11 out of 16 districtshave a significant problem. It

must be recognised that all theavailable clinical and biochemi-cal indicators are subject to limi-tations. And therefore WHO hasrecommended that at least 2 in-dicators should be used for as-sessing the vitamin A status of apopulation (13).

Sub-clinical deficiency: It is wellrecognised that xeropthalmiarepresents an advanced state ofdeficiency. In communities whereclinical signs of VAD are seen,sub-clinical deficiency can beexpected to be more common.Large-scale data on serum reti-nol levels are not available toassess the extent of biochemicaldeficiency. But the communitystudies carried out in AndhraPradesh (14), Tamilnadu (15) andUttar Pradesh (11) indicate that30–50% of children have retinollevels below 20 µg/dl, the WHOcut-off indicating a public healthproblem. These observations arecorroborated by the dietary data.Green leafy vegetables, milk andmilk products are the majorsources of vitamin A in Indian di-ets. Surveys carried out in differ-ent parts of the country show lowconsumption of these foods (16).The average intake of vitamin Ais around 300 µg in women and120 µg in children, and more than80% have intakes less than 50%of the recommended dietary al-lowance (RDA).

Thus the available data show thatthough the severe forms of blind-ing malnutrition have declined inthe last two decades, mildergrades of VAD still exist in manyparts of India. National surveysprovide only state level informa-tion and the limited data availablefrom district surveys show a widevariation between the districts.The magnitude of the public

health problem varies dependingupon the areas surveyed and theindicators used.

Is mild VAD a publichealth concern?

Apart from causing ocular signsVAD is known to produce sys-temic changes, of which the mostsignificant effects are alterationsin epithelial integrity and immunestatus. Evidence for an associa-tion between VAD and infectionwas documented by Scrimshawet al. some 30 years ago (17).Since then, supporting data fromanimal experiments and observa-tional studies in humans havebeen published (18). Positiveassociation between mildxeropthalmia and the risk of res-piratory infection was reported inIndian children (19), while Indo-nesian children showed an asso-ciation with both diarrhoea andrespiratory infection (20). Chil-dren with clinical signs of VADwere found to be at greater riskof death than those without (21).A subsequent intervention trial inIndonesia showed a 34% reduc-tion in mortality among childrenreceiving six monthly doses of200,000 IU vitamin A (22). Thiseffect was seen even in childrenwithout clinical signs, highlightingthe importance of sub-clinicaldeficiency. Controlled trials inother countries also resulted in asignificant reduction in mortality-19% in Ghana (23) and 30% inNepal (24). The reduction wasattributed to a fall in deaths re-lated to diarrhoea and measles.However, studies in India (25)and Sudan (26) using the samedose showed no effect. Trials ofweekly supplements in India (15)and food fortification in Indone-sia (27) showed higher reduction


in mortality, indicating that thebeneficial effect was due to im-provement in vitamin A status bywhatever means. A meta-analy-sis of data from eight interventiontrials in pre-school childrenshowed an average of 23% re-duction in total mortality (28).However, this conclusion hasbeen challenged because theresults are not consistent (29).Subsequent studies in infantsless than 6 months old have alsoshown variable results. Adminis-tration of a single dose of 50,000IU of vitamin A to neonates in In-donesia resulted in a significantreduction in mortality risk (30),while a similar trial in Nepalshowed no effect (31). In a WHOmulticentre trial in Peru, Ghanaand India, vitamin A supplements(25,000 IU) given along with DPTimmunisation at 6, 10 and 14weeks did not affect morbidity ormortality (32).

There are a number of potentialexplanations for the variability inresults across trials. These in-clude age of the children and thedosage schedule; smaller andfrequent doses seem to be moreprotective than large periodicdoses. High prevalence of infec-tions resulting in vitamin lossesand depletion of stores canshorten the protective period ofsupplements. Vitamin A is likelyto have a greater effect in areaswhere VAD is highly prevalent.Other factors like concomitantnutritional deficiencies and ac-cess to healthcare can alsomodify the mortality effect. Thusthe impact of vitamin A may varydepending upon environmentalconditions. An average 23% re-duction in mortality may not beapplicable to all ecological set-tings, but the positive impact ofvitamin A in some situations can-not be denied.

After reviewing the studies on vi-tamin A and mortality, a NationalConsultation on the Benefits andSafety of Vitamin A Administra-tion, held in New Delhi in Sep-tember 2000, concluded that thedata are “not robust” enough torecommend vitamin A supple-mentation for the purpose of mor-tality reduction in children (33). InIndia, infant deaths comprise upto 80% of under-five mortality insome states and therefore it isargued that an intervention withpossible effects only beyond in-fancy will not be of much valuefor reducing child mortality (34).

It is true that vitamin A is not apanacea for all the illnesses thataffect children in developingcountries. However, the need forimproving vitamin A status can-not be denied. The fact that amajority of the population sub-sists on inadequate diets, with

1977

1990

1996

50

40

30

20

10

0

Vitamin A Milk and

milk-products

GLV

22 21191313

22

37 33 42

% R

DA

60

Figure 2. Vitamin A intakes in pre-school children.


vitamin A intakes less than halfthe recommended level and asignificant proportion of childrenhaving clinical and sub-clinicaldeficiency is a matter of publichealth concern. The aim of theNational Nutrition Policy is notonly to prevent blindness in chil-dren, but also to eliminate VADas a public health problem. Thereis thus a need to accelerate theintervention efforts to achieve thegoal.

What are the appro-priate strategies forVAD control?Multiple approaches including vi-tamin A supplementation, foodfortification, dietary diversificationand public health measures havebeen suggested for preventionand control of VAD. Although pi-lot projects have demonstratedtheir efficacy and feasibility, large-scale implementation of theseprograms have met with limitedsuccess. This has led to consid-erable debate as to which of theinterventions is most cost-effec-tive and sustainable. The choiceis not simple. Each one has itsstrengths and limitations. Formaximum impact and efficacy,each strategy should be consid-ered in the context of a country’sneeds/priorities and its capacityto implement and sustain an in-tervention.

Vitamin A supplementation is thequickest way of improving the vi-tamin A status of a population andis the choice of strategy in areaswhere the problem is widelyprevalent. Improving the diet,even if it is difficult to achieve inthe short term, is of paramountimportance, as it contributes toimproving the overall nutritional

status. Food fortification with vi-tamin A has proved to be an ef-fective strategy for reducing VADin some countries. A right mix ofinterventions tailored to the localcircumstances is more likely tosucceed in achieving the objec-tive.

In India, the National Vitamin AProphylaxis Program was startedwith the primary aim of reducingblindness in children, which wasa significant problem at that time.Under this program sponsored bythe Ministry of Health and Fam-ily Welfare, children aged be-tween 1 and 5 years were givenoral doses of 200,000 IU vitaminA every 6 months. Evaluationstudies in the late 1970s revealedpoor implementation of the pro-gram and inadequate coveragein most of the states (35). Theprogram was reviewed severaltimes since then, and efforts weremade to correct existing deficien-cies. Currently, vitamin A is givenonly to children aged less than 3years who are at greater risk, andadministration of the first twodoses is linked with routine im-munisation to improve coverage.100,000 IU of vitamin A are givenalong with measles vaccine at 9months of age and 200,000 IUwith DPT booster at 15 months(36).

In recent years, there has beenconsiderable debate on the con-tinuation of the vitamin A supple-mentation program. Sincekeratomalacia/blindness is nolonger a significant problem, it isargued that there is no need forsupplementation and that milderforms of deficiency can be tack-led through alternate strategiesaiming at dietary improvement(29). It is true that dietary inter-vention is the most logical ap-

proach. Right from the beginning,supplementation was conceivedas an interim measure to be dis-continued once the dietary im-provement was achieved. Unfor-tunately, the dietary situation hasnot changed in the last three dec-ades (Figure 2). Vitamin A intakeof children is less than half theRDA even today, with a signifi-cant proportion of them havingclinical evidence of deficiency.Under these circumstances, it isnot wise or ethical to withdraw thebenefits of supplementation.

There is also a controversy aboutthe universal approach currentlyadopted, because VAD is notuniformly spread throughout thecountry (29, 34). The cost of avitamin A supplement is esti-mated to be Rs. 3.20 (0.06 USD)per child per year, which is a neg-ligible proportion of the totalhealth expenditure (37). A selec-tive approach, covering only thedistricts where VAD is a publichealth problem, would be a morecost-effective strategy. It requiresdistrict mapping for VAD signs allover the country. This is possibleif the states take responsibility forconducting surveys and monitor-ing the program. When such dataare not available, priority shouldbe given to backward areas,identified by the ecological indi-cators.

The mode of delivery of the vita-min has also been a subject ofintense discussion. Under thenational programme, children aregiven vitamin A along with rou-tine immunisation (measles, po-lio and DPT). While the interna-tional agencies have been vigor-ously promoting supplementationlinked with routine as well ascampaign-based immunisation, itis regarded not as a short-term


measure but as a low-cost sus-tainable strategy to combat VADin developing countries (38). Ef-forts are also made to expand theprogram to cover pregnant andlactating women, and infants be-low 6 months, though studieshave failed to demonstrate clearbenefits in these groups (39).These efforts have met great re-sistance in the Indian context. Inrecent years, Pulse Polio Immu-nisation (PPI) has been imple-mented as a national campaign,offering an opportunity for deliv-ering vitamin A. But the IndianAcademy of Paediatrics disap-proved linking vitamin A with PPI,primarily due to lack of sufficientevidence for the benefit of sup-plements in infancy, chances ofdestabilisation of routine servicesand the fact that PPI is a tempo-rary program (40). Of the twostates which included vitamin Ain the PPI campaigns during1990–2000, improved coveragewas achieved in Orissa but notin Uttar Pradesh due to poor lo-gistic support (11). Consideringthe inconsistent results and thefact that PPI itself is coming toan end, the National Consultationon Vitamin A also recommendedthat vitamin A should not belinked with PPI. Instead, the on-going program of supplementa-tion linked with routine immuni-sation should be strengthened toachieve high coverage (>90%)for at least the first two doses(33). There is also a need tostrengthen the education compo-nent of the program to improvethe diet as a long-term goal.

Dietary improvement is, undoubt-edly, the most logical and sustain-able strategy to prevent VAD. Itscontribution to improvement inoverall nutrition justifies contin-ued efforts in this direction. There

is a general consensus on this atboth the national and interna-tional levels. However, past ef-forts concentrated on supple-mentation and not much attentionwas paid to planning and imple-mentation of food-based pro-grammes. It is often stated thatgreen leafy vegetables (GLV) andfruits are available in plenty dur-ing the season and well within theeconomic reach of even the poor(29). Availability alone, however,does not ensure programmaticsuccess. This requires a changein dietary habits and increasedaccess to vitamin A-rich foods. Inrecent years, efforts have beenmade to achieve these objectivesthrough educational and horticul-tural interventions. However,these are mostly small-scaleprojects and are yet to be incor-porated into national pro-grammes. Even these projectshave failed to demonstrate a sig-nificant impact on vitamin A sta-tus because they focussed onGLV as the main source of vita-min A (41). Bioavailability of β-carotene is lower from GLV thanfrom other vegetables and fruits.Young children cannot consumeleafy vegetables in sufficientquantities to meet the vitamin Arequirement. Based on feedingtrials with selected vegetables, afactor of 26 (instead of 6) hasbeen suggested for conversion ofβ-carotene to vitamin A (42).However, this is debated be-cause bioavailability of carotenevaries widely and depends notonly on the food source but alsoon the way it is prepared, as wellas on the level of other dietarycomponents like fibre and fat. Adetailed discussion of this issueis beyond the scope of this pa-per. But it must be admitted thatpromotion of GLV alone is un-likely to eliminate VAD. Dietary

diversification programmes mustinclude a variety of vegetablesand fruits as well as animal foodslike milk and eggs. We should notjust settle for something “cheap”,but make all efforts to improve thequality of diet.

What went wrongwith the vitamin Acampaign inAssam?

The reported deaths of over adozen children and a largenumber of children falling sickafter vitamin A administration dur-ing a mass campaign in thenorth-eastern state of Assam hascaused considerable anxiety andconcern among health profes-sionals (1-3). The campaign wasstopped immediately and an in-quiry was set up by the Govern-ment. Some doctors blamed thestock of vitamin A supplied. How-ever, testing of vitamin A samplesfrom batches used in the cam-paign showed nothing wrong withthe vitamin supplied (43). Theyconformed to the standards ofquality specifications, so the re-ported adverse reactions werenot attributable to the quality ofthe product supplied.

Some nutritionists have ques-tioned the campaign approachadopted by the state, when thenational guidelines recommendvitamin A administration alongwith routine immunisation (44).Unfortunately, the national immu-nisation coverage is also low(49%). According to NFHS-2, thenational coverage for at least onedose of vitamin A (linked with im-munisation) is only 30% and inAssam, it is even lower at 15.4%(45). Recently, some of the states


in India including Assam haveinitiated a vitamin A campaign,with UNICEF support, to improvethe coverage. This is the thirdround of vitamin A distribution inAssam, and the first two roundsin this state as well as otherstates of Andhra Pradesh,Karnataka and Orissa were un-eventful. During this round,UNICEF has replaced the tradi-tional 2 ml spoons with 5 ml cupsfor administering vitamin A. It ispossible that this switch in themethod and inadequate trainingof health workers might have ledto overdosing in some cases.Though the cup had 2 ml mark-ings, health workers cannot beexpected to measure the doseaccurately, especially in a masscampaign where hundreds ofchildren are covered in a day.

Administration of large doses ofvitamin A is known to produceside effects like headache, vom-iting and bulging fontanel in 1–2% of children, but these symp-toms are mild and disappearwithin 48 hours (46). Accordingto the newspaper reports, up to15,000 children, out of the 3 mil-lion who received vitamin A dur-ing the campaign, became ill(47). This is much less than whatis expected (up to 60,000) withvitamin A dosing.

The Assam episode started withthe death of a two-year-old childfrom the Tea garden community,after consuming vitamin A. Thistriggered panic amongst the par-ents, and thousands of peoplerushed with their children to thenearest health centre, some ofthem complaining of fever, vom-iting and diarrhoea. Normally,these symptoms do not attractmass attention. But the mediahas sensationalised the event in

Assam leading to a wave of massconcern. All deaths and illnessesthat occurred in children duringthe following week were attrib-uted to vitamin A. There is noevidence that vitamin A will causedeath even if a child had receivedtwice the amount (400,000 IU).This is the dose recommendedby the WHO for the treatment ofxeropthalmia (48). Vitamin A pro-grammes have been in operationfor the past several years not onlyin India, but also in 60 other coun-tries. So far, not a single case ofdeath attributable to vitamin Adosing was reported. Lethal doseof vitamin A is not known, but areview of the case reports of chil-dren getting 300,000–900,000 IUdo not suggest severe toxic ef-fects that could be fatal (49). It isnot surprising that the investiga-tion conducted by the State De-partment of Health and UNICEFrevealed that in most of the casesdeath was due to causes unre-lated to vitamin A (50). Thesewere cardiac failure, severeanaemia, high fever, foreign bodyaspiration etc. Considering thecurrent mortality rate of 28/1000in children aged 1–4 years (45),15 deaths reported in the weekfollowing vitamin A administrationare far less than the expectednumber.

Inadequate training of healthworkers, lack of supervision andnegligence of children who devel-oped symptoms might have con-tributed to the confusion. Thereare important lessons to be learntfrom this episode. A communitymay lose faith in government-sponsored public health pro-grammes if adequate precau-tions are not observed. Majorprecautions for vitamin A areavoiding massive doses in younginfants and ensuring that the

dose limit is not exceeded andthat the administration is carriedout by trained health workersunder strict supervision. Ad-equate steps should be taken toeducate the community about thebenefits of vitamin A supplemen-tation and the possibility of tran-sient side effects. Extra precau-tions are needed for treating sickchildren. WHO has recom-mended that sick children whoare at greater risk, particularlythose with measles and severeprotein-energy malnutritionshould be given an additionaldose of vitamin A (48). However,this approach can create prob-lems if adequate precautions arenot taken. If a child who is seri-ously ill dies after receiving thedose, vitamin A may be blamedas the cause of death (as it hap-pened in Assam). Such casesshould be referred to the nearesthealth centre for full treatment.Efficient management is crucialfor success of any public healthprogram.

ConclusionVAD still exists as a public healthproblem in many parts of Indiaand there is a need for continuedefforts to improve vitamin A sta-tus of the population. It is unfor-tunate that the Assam episodeled to so much controversy,putting an end to the vitamin Acampaign even in other states.However, this should be viewednot as a set-back, but as an op-portunity to strengthen the ongo-ing programme of supplementa-tion linked with routine immuni-sation and accord higher priorityto dietary approaches as a long-term sustainable solution.


References

1. Mudur G. Deaths trigger fresh con-troversy over vitamin A programmein India. BMJ 2001, 323: 1206

2. Sharma DC. UN vitamin A campaignin India under fire. Lancet 2001, 358:1791

3. Probe ordered into vitamin A deaths.The Times of India, New Delhi. 14November 2001

4. Kapil U. Administration of massivedose of vitamin A and related deathsin India. Electronic responses toMudur, BMJ 2001, 323: 1206

5. Bhattacharya AK, ChatopadhyayaPS. Bulletin of the Calcutta Schoolof Tropical Medicine 1986, 34: 44-47

6. National Nutrition Monitoring Bureau.Report of repeat survey (1989–1990). National Institute of Nutrition,Hyderabad

7. Ghosh S. Combating vitamin A defi-ciency – A rational public health ap-proach. NFI Bulletin. January 2001,vol 22, No. 1

8. National Nutrition Monitoring Bureau.Report of second repeat survey –rural (1996-1997). National Instituteof Nutrition, Hyderabad

9. India Nutrition Profile, Ministry ofHuman Resource Development.Government of India, 1998

10. Chakravarty I. Ghosh K. Micronutri-ent malnutrition – present status andfuture remedies. J Ind Med Assoc2000, 98: 539

11. Vir SC. Linkage of vitamin A massivedose supplementation with pulsepolio immunisation – an overview. Areport on benefits and safety of ad-ministration of vitamin A to preschoolchildren and pregnant and lactatingwomen. Ed. Chapel U, Srivastava,New Delhi

12. Report of District Nutrition Project.Indian Council of Medical Research,1999

13. Indicators for assessing vitamin Adeficiency and their application inmonitoring and evaluating interven-tion programmes. World Health Or-ganization, Geneva, 1996

14. Bhaskaram P et al. Effect of subclini-cal vitamin A deficiency and admin-istration of vitamin A as a single dose

on immune functions in children. NutrRes 1989, 9: 1017

15. Rahmatullah L, Underwood BA,Thulasiraj RD, Milton RC,Ramaswamy K, Rahmatullah R,Babu G. Reduced mortality amongchildren in southern India receivinga small weekly dose of vitamin A.N Engl J Med 1990, 323: 929-935

16. National Nutrition Monitoring Bureau.Report on food and nutrient intakesof individuals – rural. 2000, NationalInstitute of Nutrition, Hyderabad

17. Scrimshaw NS, Taylor CE, GordonJE. Interactions of nutrition and in-fection. World Health Organization,Geneva, 1968

18. Sommer A, West KP. Vitamin A defi-ciency, health, survival and vision.New York: Oxford University press;1996

19. Milton RC, Reddy V, Naidu AN. Mildvitamin A deficiency and childhoodmorbidity – an Indian experience. AmJ Clin Nutr 1987, 46: 827-829

20. Sommer A, Katz J, Tarwotjo I. In-creased risk of respiratory diseaseand diarrhea in children with pre-ex-isting mild vitamin A deficiency. Am JClin Nutr 1984, 40: 1090-1095

21. Sommer A, Hussaini G, Tarwotjo I,Susanto D. Increased mortality inchildren with mild vitamin A defi-ciency. Lancet 1983, 2: 585-588

22. Sommer A, Tarwotjo I, Djunaedi etal. Impact of vitamin A supplementa-tion on child mortality. A randomisedcontrolled community trial. Lancet1986, 1: 1169-1173

23. Ghana VAST Study Team. Vitamin Asupplementation in northern Ghana:effects on clinic attendances, hospi-tal admissions and child mortality.Lancet 1993, 342: 7-12

24. West KPJ, Pokhrel RP, Katz J et al.Efficacy of vitamin A in reducing pre-school child mortality in Nepal. Lan-cet 1991, 338: 67-71

25. Vijayaraghavan K, Radhiah G,Prakasam BS, Sarma KVR, ReddyV. Effect of massive dose vitamin Aon morbidity and mortality in Indianchildren. Lancet 1990, 336: 1342-1345

26. Herrera MG, Nestel P, El Amin A,Fawzi WW, Mohamed KA, Weld L.Vitamin A supplementation and childsurvival. Lancet 1992, 304: 207

27. Muhilal, Permeisih D, Idradinata YR,Muherdiyantinsih, Karyadi D. VitaminA fortified monosodium glutamateand health, growth and survival ofchildren: a controlled field trial. Am JClin Nutr 1988, 48: 1271-1276

28. Beaton GH, Martorell R, Aronson KJet al. Effectiveness of vitamin A sup-plementation in the control of youngchild morbidity and mortality in de-veloping countries. ACC/SCN Stateof the Art Series. Nutrition policy dis-cussion paper No. 13, 1993. WorldHealth Organization, Geneva

29. Gopalan C. Prevention of micronu-trient malnutrition. NFI Bulletin, Oc-tober 2001, vol 22, No. 4

30. Humphrey J, Agoestina T, Wu L etal. Impact of neonatal vitamin A sup-plementation on infant morbidity andmortality. J Pediatr 1996, 128: 489-496

31. West KP, Katz J, Shresta SM et al.Mortality of infants <6 months of agesupplemented with vitamin A: arandomised, double-masked trial inNepal. Am J Clin Nutr 1995, 62: 143-148

32. WHO/CHD Immunisation-linked vita-min A supplementation study group.Randomised trial to assess benefitsand safety of vitamin A supplemen-tation linked to immunisation in earlyinfancy. Lancet 1998, 352: 1257-1263

33. A report on national consultation onbenefits and safety of vitamin A ad-ministration to pre-school childrenand pregnant and lactating women.Conclusions and recommendations.Ministry of Health & Family Welfare,New Delhi, 2000

34. Choudhary P. Does India need vita-min A mega dose supplementationfor children? A report on national con-sultation on benefits and safety ofvitamin A administration to preschoolchildren and pregnant and lactatingwomen. Ed. Kapil U, Srivastava. Min-istry of Health and Family Welfare,New Delhi, 2000

35. Vijayaraghavan K, Rao NP. An evalu-ation of the National Prophylaxis Pro-gramme against blindness due to vi-tamin A deficiency. Nutr Rep Int 1982,25: 341-441

36. Report of the workshop to reviewprograms for control of vitamin A de-ficiency in India. Ministry of Healthand Family Welfare, New Delhi, 1997


37. Pandav CS, Anand K, Gupta S,Murthy GV. Cost of vitamin A and ironsupplementation to at risk popula-tion. Indian J Pediatr 1998, 65: 849-856

38. Vitamin A Global Initiative; a strategyfor acceleration of progress in com-bating vitamin A deficiency. UNICEF/MI/WHO/CIDA/USAID, 1998

39. Reddy V. Vitamin A supplementationof lactating mothers and young in-fants – no clear benefits. Nutrisearch,Bulletin of IAP Subspecialty Chap-ter on Nutrition, 2001; vol 8, No. 1

40. IAP policy on linking vitamin A topulse polio programme. IndianPediatr 2000, 37: 727

41. Viajayaraghavan K, Nayak U, BamjiMS, Ramana GNV, Reddy V. Home-gardening for combating vitamin A

deficiency in rural India. Food andNutrition Bulletin,1997, 18: 337-343

42. de Pee S, West CE, Permaesih D,Maruti S, Muhilal, Hautvast JG. Or-ange fruit is more effective than aredark green leafy vegetables in in-creasing serum concentration of reti-nol and β-carotene in school childrenin Indonesia. Am J Clin Nutr 1998,68: 1058-1067

43. Lab clean chit to vitamin A. The Tel-egraph, Guwahati, 22 November2001

44. Kapil U. Administration of massivedose of vitamin A and related deathsin India. BMJ 2001, 323: 1206

45. National Family Health Survey(NFHS-2) 1998–1999. InternationalInstitute for Population Sciences,Bombay

46. Vijayaraghavan K, Rao NP, SarmaKVR, Reddy V. Impact of massivedoses of vitamin A on incidence ofnutritional blindness. Lancet 1984, 2:149

47. India Times News. 13 November2001

48. Sommer A. Vitamin A deficiency andits consequences: A field guide todetection and control. World HealthOrganization, Geneva, 1996

49. Bauernfeind JC. The safe use of vi-tamin A. A report of the Internationalvitamin A Consultative Group. Wash-ington, DC, 1980

50. UNICEF-sponsored program goneawry. India’s National Magazine, TheHindu. 8-21 December 2001, Issue25


A combined approach to vitamin A deficiencyin ThailandEmorn Wasantwisut, Institute of Nutrition, Mahidol University, Thailand

Historical back-ground: 1960–1990

A survey conducted in 1960 bythe United States Interdepart-mental Committee on Nutritionfor National Defense (ICNND)indicated that Thailand had a vi-tamin A deficiency problem (1).This was further confirmed byvarious community surveys andhospital records and led to therecognition of vitamin A defi-ciency as one of the seven na-tional nutrition problems in Thai-land’s Fourth National Economicand Social Development Plan(NESDP) during 1977–1981.Since the problem of vitamin Adeficiency occurred primarily inpocket areas and its prevalencetrailed behind those of protein-energy malnutrition, iron-defi-ciency anemia and iodine defi-ciency disorders, the nationalnutrition programs were notaimed specifically at vitamin Adeficiency. Rather, vitamin A con-siderations were integrated intoThailand’s health and nutritionpolicies, plans and programsalong with other nutritional prob-lems. Under the Fifth NESDP(1982–1986), Thailand launchedan intensive programme nation-wide to reduce poverty, improveprimary healthcare services, andincrease household food securityamong rural poor families (2).Nutrition programs became a partof the Poverty Alleviation Plan,which linked together the activ-

ities of four major ministries:Health, Agriculture, Educationand Interior. The strategies in-cluded programs such as growthmonitoring, nutrition education,horticulture, supplementary feed-ing, school lunch etc. These ef-forts led to a marked decline inclinical vitamin A deficiency suchthat in 1985 the World HealthOrganization (WHO) classifiedThailand as a country where vi-tamin A deficiency was not a pub-lic health problem, although spo-radic cases might occur (3).

By the end of the fifth NESDP,case reports of xerophthalmiabecame rare and the country be-gan to enter a transition from se-vere to moderate degrees of de-ficiency (4). This was confirmedby a 1990 prevalence survey ofvitamin A deficiency in northernand northeastern Thailand whichfound no case of xerophthalmia,but approximately one-fifth ofpreschool children in these re-gions manifested low liver stores(relative dose response test) andabnormal conjunctival epithelium

Figure 1. Ivy gourd plant (Coccinia indica).


(5). Since vitamin A deficiencyproblems in the north and north-east regions of Thailand are mar-ginal, an intervention to promoteconsumption of locally availablevitamin A-rich foods seems mostappropriate. Despite the fact thatvitamin A-rich foods such as yel-low and orange fruits and vegeta-bles, dark green leafy vegeta-bles, liver, eggs and whole milkare readily available in most ar-eas, they are underutilised dueto such factors as consumptionbehaviour, seasonal variationand food appeal. Recent experi-ence in northeast Thailand on thesocial marketing of the ivy gourdplant (Coccinia indica as shownin Figure 1), which is rich in pro-vitamin A carotenoids, demon-strated that significant changesin dietary habits can be achievedin a relatively short time (6). Afollow-up study of the social mar-keting project showed a sus-tained improvement in the con-sumption of ivy gourd and othervitamin A-rich foods as well asdietary fat, leading to a significantincrease in serum retinol concen-trations in preschool children (7).

Xerophthalmia inlower southernThailand: astepwise and com-bined approachWhereas the problem in the northand northeast regions appears tobe marginal, a hospital-basedrecord in Yala province, southernThailand, during 1988–1991 re-vealed alarming evidence of 31cases of xerophthalmia among3–15 months old infants (8).These infants were diagnosedwith severe protein-energy mal-nutrition together with diarrhoea

and pneumonia. They receivedlittle or no breast-feeding and in-stead were given non-fortifiedsweetened condensed milk. Asurvey in 1992 in the lower south-ern region confirmed the serious-ness of the situation among pre-school children (2–6 years old)as evidenced by keratomalacia,low serum retinol and depletedliver stores (9). The surveyhelped to identify priority areasfor interventions. To counteractthe problem, the Ministry of Pub-lic Health launched a stepwiseand combined approach.

Supplementation

A universal distribution of high-dose vitamin A capsules waslaunched in 1992 for all childrenunder five years of age residingin the three southernmost prov-inces of Yala, Pattani andNarathivat. The capsules weresupplied by the Task ForceSIGHT AND LIFE and the RoyalThai Government. Vitamin A cap-sules were distributed every sixmonths and the supplementation

program covered the period from1992 to 1998. Besides healthworkers, traditional birth attend-ants were also trained to admin-ister these supplements. In addi-tion, the Ministry of Public Healthstrengthened supportive meas-ures such as maternal and childcare, immunisation, control of in-fection etc through workingclosely with the regional and lo-cal health officers. These com-bined efforts resulted in no newreported cases of xerophthalmia(10).

Fortification

Consumption of non-fortifiedsweetened condensed milk wasa common practice and an impor-tant risk factor for infants in theendemic area, especially amongthe families of migrant rubberplantation workers. This productwas attractive, due to its readilyaccessible nature, low cost andconvenience. To effectively curbthe problem, the Ministry of Pub-lic Health officers in collaborationwith researchers at the Institute

Figure 2. A meeting with mothers in lower southern Thailand on indigenousvitamin A-rich foods.


of Nutrition, Mahidol University(INMU), compiled a case for vi-tamin A fortification of all brandsof sweetened condensed milk.The major thrust behind thismovement was the indication thatxerophthalmia involving the cor-nea occurred when the mothersor guardians changed from a for-tified to a non-fortified brand ofmilk because of the lower cost ofthe latter. The rationale to fortifysweetened condensed milk withvitamin A was to prevent any childfrom becoming blind as a resultof being fed this food because oflack of knowledge. A meeting todiscuss this matter with themanufacturers resulted in a will-ingness to cooperate in the forti-

fication program. In 1993, theCommittee under the Food andDrug Administration passed aregulation that sweetened con-densed milk be fortified with vita-

min A at a dose of 330 retinolequivalents (RE) per 100 g (11).

Dietary diversification

In 1995, a survey of vitamin Adeficiency among preschool chil-dren in the lower southern regionrevealed no new cases ofxerophthalmia. In addition, vita-min A status improved markedlyas evidenced by serum retinolconcentrations and liver stores ofvitamin A estimated by the modi-fied relative dose response test(12). The severity of the situationhad declined. Therefore, the Min-istry of Public Health in collabo-ration with the INMU researchteam decided to plan a dietarydiversification program to pro-mote consumption of local foodsrich in vitamin A. Since the lowersouthern provinces are inhabitedby a Thai Muslim population, aformative research was first con-ducted to collect data on poten-tial sources, availability and con-sumption patterns of indigenousfood sources. These data wereconfirmed with mothers (Figure2), child caretakers and commu-nity elders. The food-based re-search (1996–1999) emphasisedtwo activities: recommendation ofvitamin A recipes for consumptionby pregnant women and devel-

Figure 3. Education material on vitamin A deficiency foruse by local health officers.

Figure 4. Reemerged case of xerophthalmia in ahill tribe child of Northern Thailand.


opment of vitamin A-rich snack(local fish chips enriched withchicken or beef liver) targeted atchildren (13). The outcomes ofboth research components wasadopted for promotion by theHealth Promotion Center insouthern Thailand as part of aspecial public event (Vitamin ADay), regular counseling andeducation programs (an exampleof education material for localhealth officers is shown in Figure3). A follow-up survey is beingplanned this year to assess thesituation.

The challengesWhile the vitamin A deficiencyproblem in lower southern Thai-land seems to be under control,a new challenge emerged in theupper northern Thailand.

In 1998, a hospital-based recordin the northern region reportedcases of xerophthalmia amongthe Karen hill tribe preschool chil-dren (Figures 4, 5) in remote vil-lages. These children were ad-mitted to the hospital with symp-toms of severe diarrhea and/orpneumonia together with a mod-

erate degree of protein-energymalnutrition. Based on the previ-ous experiences in the lowersouthern provinces, the Ministryof Public Health immediatelylaunched a distribution of high-dose vitamin A capsules in en-demic areas together with effortsto strengthen other supportivepublic health measures. In addi-tion, a committee at a provinciallevel has been formed to inte-grate related activities amongvarious sectors of health, agricul-ture, education and interior min-istries. The efforts, so far, haveresulted in no new reportedcases of xerophthalmia in thearea. Besides, the Ministry ofPublic Health has also supportedan ongoing research program incollaboration with the INMU re-search team to explore ways toimprove diet and nutritional sta-tus in this population.

It is apparent that the challengesfacing Thailand are to effectivelyprevent the eruption of sporadiccases of vitamin A deficiency andto successfully improve vitaminA nutrition among vulnerablepopulations in a sustainable man-ner. An ongoing effort to develop

a surveillance system to includevitamin A, an incorporation of vi-tamin A into a multiple micronu-trient intervention program, a set-up of program monitoring andevaluation components etc areparts of the tasks undertaken bythe Ministry of Public Health incollaboration with academic insti-tutes like INMU and other part-ners to bring the vitamin A defi-ciency problem under control,once and for all.

References

1. US Interdepartmental Committee onNutrition for National Defense. King-dom of Thailand nutrition survey Oc-tober–December, 1960. Washington,DC: Department of Defense, 1962

2. Tontisirin K, Kachondham Y,Winichagoon P. Trends in the devel-opment of Thailand’s nutrition andhealth plans and programs. Asia PacJ Clin Nutr 1992, 4: 100-107

3. World Health Organization. Preven-tion and control of vitamin A defi-ciency, xerophthalmia and nutritionblindness: summary of a proposal fora ten-year program of support tocountries. Geneva: WHO, 1985

4. Dhanamitta S, Viriyapanich T,Kachonpadunkitti Y. Vitamin A defi-ciency in Thailand. In: Yasumoto K,Itokawa Y, Koichi H, Sanno Y, eds.Proceedings of the Fifth Asian Con-gress of Nutrition, Osaka, Japan.Tokyo: Center for Academic Publica-tions, 1988: 198-201

5. Nutrition Division. Report on theprevalence of inadequate vitamin Anutriture in preschool children ofnorth and northeast Thailand. Bang-kok: Ministry of Public Health andInstitute of Nutrition at Mahidol Uni-versity, 1991

6. Smitasiri S, Attig GA, Dhanamitta S.Participatory action for nutrition edu-cation: social marketing vitamin A-rich foods in Northeast Thailand. EcolFood Nutr 1992, 28: 199-210

7. Smitasiri S, Sa-ngobwarchar K,Kongpunya P, Subsuwan C, BanjongO, Chitchumroonchokchai C,Rusamisopaporn W, Veeravong S,Dhanamitta S. Sustaining behav-

Figure 5. The girl is blind in one eye. She had a VAD prob-lem in younger years.


ioural change to enhance micronu-trient status through community- andurban-based intervention in north-east Thailand: vitamin A. Food NutrBull 1999, 20: 243-231

8. Poolpinyo T. Xerophthalmia inpediatric patients in Yala Hospital.12th Reg Med J 1992, 3: 19-20

9. Nutrition Division. Vitamin A defi-ciency among preschool children infive southernmost provinces of Thai-

land. Bangkok; Thailand, Ministryof Public Health, 1995

10. Thainuea V, Wasantwisut E, AttigGA. Thailand’s battle against nu-tritional blindness. World Health1995, 5: 27

11. Wasantwisut E, Chittchang U,Sinawat S. Moving a health sys-tem from a medical towards a di-etary approach in Thailand. FoodNutr Bull 2000, 20: 157-160

12. Nutrition Division. Formative evalu-ation of vitamin A deficiency controlamong preschool children in the fiveprovinces of the southernmost Thai-land. Bangkok, Thailand: Ministry ofPublic Health, 1997

13. Chittchang U, Jittinandana S,Sungpuag P, Chavasit V, Wasant-wisut E. Recommending vitamin A-rich foods in southern Thailand. FoodNutr Bull 1999, 20: 238-242


Progress and challenges in controllingvitamin A deficiency in the PhilippinesFlorentino S. Solon, MD, President and Executive Director, Nutrition Center of thePhilippines, Taguig Metro Manila, Philippines

The Philippines has made fairlygood progress in the control ofvitamin A deficiency (VAD) in thepast 15 years, from 1982 to 1998.The Food and Nutrition ResearchInstitute (FNRI) of the Depart-ment of Science and Technology(DOST) has been conductingNational Nutrition Surveys (NNS)every five years, starting in 1975,

followed in 1982, 1987, 1993 and1998. The 1993 NNS revealedthat the prevalence of clinicalsigns of VAD, i.e. a combinationof night blindness (XN) and Bi-tot’s spots (X1B), among pre-school children (6–60 monthsold) decreased from 3.5% in1982 to 0.50% in 1993 (Figure 1)(1-3). This figure is slightly lower

than the 1995 World Health Or-ganization’s (WHO) estimatedoverall prevalence for developingcountries, which is 0.6% amongpreschool children (4). The trendshowed a 2.5 percentage point(pp)-reduction over a 10-yearperiod (or a 78% reduction in 10years), better than the WHO es-timated trend change of 0.43 pp/10 years for developing countries(Table 1) (5).

Most deficiencies are “sub-clini-cal” based on serum retinol con-centration. The FNRI nationalprevalence estimate of deficientconcentration (<0.35 µmol/l)among preschool childrenshowed a decrease in proportionfrom 10.4% in 1993 to 8.2% in1998 (6). However, this figure ishigher than the 5% cut-off thatidentifies VAD as a public healthproblem. The sub-clinical VADprevalence of deficient and lowconcentration (<0.70 µmol/L) hasincreased from 35.8% in 1993 to38.0% in 1998 (Figure 2).

Sub-clinical VAD (<0.70 µmol/l)among preschool children ispresent in all of the 16 regions inthe country (Figure 3). Further,eight provinces and five munici-palities in Metro Manila havebeen identified as areas of high-risk regions (7). On the otherhand, prevalence of sub-clinicalVAD among pregnant women in-creased from 1993 to 1998 whilethat among lactating women

Table 1.Trends in the prevalence of clinical signs of VAD in thePhilippines

Indicator Prevalence Trend% Change1982 1993 (pp/10 years) per 10 years

Total X1B, XN 3.20 0.50 -2.50 -78.0

Source: The Micronutrient Initiative (MI), (1998). Progress in controllingvitamin A deficiency

1982

1.8

1.4

0.7

0.2

0.4

0.1

1987

Year

1993

% p

re

va

len

ce

0

2

1

night blindness

Bitot's spots

Figure 1. Prevalence of clinical vitamin A deficiency among pre-school chil-dren in the Philippines 1982, 1987, 1993 (source: Food and Nutrition Re-search Institute. 1982, 1987 and 1993 National Nutrition Surveys).


showed no change (Figure 4).Maternal night blindness (XN) of10% was also reported in the1998 survey (8).

A general decrease in the con-sumption of various foods is ob-served from 915 g/day in 1982to 803 g/day in 1993 (7). Specifi-cally, vitamin A-rich food intakein rural areas was only 74% ad-equate, mostly coming from foodof plant origin (9). In addition, pre-cipitating events, particularly di-arrhoea, respiratory disease,measles, and protein-energymalnutrition are still the leadingmorbidity among preschool chil-dren in the country. In spite ofthese contributory factors that areassociated with the occurrence ofVAD, including the political andeconomic upheaval the countrywas experiencing over the years,vitamin A status improvement hasbeen encouraging.

The nationwide fight against VADbegun in 1974 upon the enact-ment of the “Nutrition Act of thePhilippines”, which mandated theformulation of the Philippine Nu-trition Program (PNP) with thespecific objective of controllingand preventing protein-energymalnutrition, VAD, iron deficiencyanemia and iodine deficiency dis-orders. The national governmentagencies in partnership with non-government organisations, im-plemented a combination of di-rect and indirect nutrition inter-ventions.

p

serum retinol level

<0.35 µmol/l

10.4 8.2

35.838.0

<0.70 µmol/l

% p

re

va

len

ce

0

40

20

30

10

1993

1998

Figure 2. Prevalence of sub-clinical vitamin A deficiency among pre-schoolchildren 1993 and 1998 (source: Philippine Nutrition Facts and Figures,FNRI, 2001).

Figure 3. Prevalence of sub-clinical VAD (serum retinol <0.70 µmol/l) amongchildren, 6 months to 5 years old, by region, Philippines, 1998 (source:Philippine Nutrition Facts and Figures, FNRI, 2001).


Nutrition programdevolved to localgovernment unitsThe government renewed itscommitment to fight malnutritionand developed the PhilippinePlan of Action for Nutrition(PPAN) in 1993. In the sameyear, the power and authority ofthe national department of agri-culture, welfare and health, in-cluding their nutrition program,were devolved to the local gov-ernment units (LGUs) (10). Thismeans more than 1000 localchief executives of the provincial,municipal and barangay (village)levels will plan and manage their

Pregnant women

16

22.2

16.416.5

Lactating women

% p

revale

nce

0

25

10

15

20

5

1993

1998

Figure 4. Prevalence of sub-clinical vitamin A deficiency among pregnantand lactating women 1993 and 1998 (source: Philippine Nutrition Factsand Figures, FNRI, 2001).

Figure 5. Short course on vitamin A and nutrition with information, educa-tion and communication as the centerpiece.

nutrition programs to solve theirmalnutrition problems. Tostrengthen the delivery system,local chief executives employbarangay workers with specifictasks and service areas: mid-wives (1:5000 population),barangay nutrition scholars (1 perbarangay) and barangay healthworkers (1:20–30 households) toeffectively deliver vitamin A andother nutrition services.

The NCP, a private, non-profitorganisation, launched an inten-sive retraining program for fieldpersonnel to strengthen the au-tonomous status of the LGUs inimplementing effective nutritionprograms. SIGHT AND LIFE sup-ported NCP’s Short CourseTraining (SCT) for the planningand management of a BarangayProgram of Action for Nutrition(BPAN), which includes vitaminA interventions (11). The mainpurpose of the training is to equipand develop local nutrition pro-gram managers and villagehealth and nutrition workers withupdated knowledge and skills for


Impressions from the “Short Course Training on nu-trition and vitamin A”

A: Introducing the use of the Nutri-Guide handbook as take-home reference IEC materials after the Nutrition Edu-cation among the mothers of malnourished children

B: Governor Pablo García of Cebu Province, Chairman ofthe Provincial Nutrition Council, together with his Nutri-tion Action Officer and Dr Florentino Solon reviewed andapproved the Cebu Plan of Action for Nutrition (CPAN)and committed to support the devolved local govern-ment unit in his province for capacity-building in themanagement of their barangay nutrition programs

C: Advocacy on a public-private partnership for a betternutrition program

D: Container gardening (in urban poor areas) of carot-ene-rich vegetables in coconut husk promoting theFood Always In The Home (FAITH) approach.

From left to right: mustard (Brassica juncea), spring on-ion, swamp cabbage (Ipomoea batatas aquatica), andmalabar nightshade or “alugbati” (Basella alba)

E: Cooking demonstration using nutritious recipes takenfrom Nutri-Guide

F: Fun-learning activities (puzzle game) on vitamin AG:“Pabasa sa Nutrisyon” or nutrition-reading session of

Nutri-Guide as a means of communicating nutritioninformation to mothers of malnourished children in thecommunity

C

D

E

F

G

B

A


effective delivery of vitamin A andother nutrition services (Figure 5).The SCT has reached 26 prov-inces and cities and trained 435provincial and municipal nutritionmanagers and 1230 villagehealth and nutrition workers.Twenty-nine more provinces aretargeted this year for SCT.

To support the LGUs’ implemen-tation of the nutrition program,heightened efforts were made ona nationwide scale for measlesimmunisation and vitamin A cap-sule (VAC) supplementation. Amicronutrient day for VAC sup-plementation was observed inApril and October of every yearsince 1993. The average cover-age is about 87% or about 8 mil-lion preschool children each year.

The food fortification programwas developed, which wasstarted with the successful forti-fication of margarine with vitaminA (12). The manufacturer of theproduct was the first to receivethe Department of Health’s sealof approval, locally called theSangkap Pinoy Seal (SPS), forproperly fortified food. The re-cently approved Food Fortifica-tion Law mandates the fortifica-tion of staple foods such as flour,cooking oil and sugar with vita-min A and encouraged fortifica-tion of processed foods. To date,there are 47 processed food prod-ucts fortified with vitamin A with theSPS. However, there is a low levelof awareness of fortified foods ingeneral, and food products withSPS in particular (13).

Conclusion and rec-ommendations

The prevalence of clinical VAD inthe Philippines has decreased by

78% in 10 years (1982–1993).Sub-clinical VAD (<0.35 µmol/l)was reduced to 8.2% in 1998from 10.4% in 1993. But the VADsituation in the country is still athreat to children’s health andsurvival. The challenge is to re-duce the prevalence of sub-clini-cal VAD (<0.70 µmol/l) amongpreschool children to a level(≤15%) that will not constitute aproblem of public health signifi-cance. The same challenge istrue for the high prevalence ofclinical and sub-clinical VADamong pregnant women.

It is recommended therefore thatthe coverage of the vitamin Asupplementation among pre-school children be intensifiedespecially in high-risk provinces.The weekly administration of 2low-dose vitamin A capsules (of10,000 IU each) to pregnantwomen starting at the 4th monthof pregnancy should be put inplace. Likewise, an increase inthe coverage of high-dose sup-plementation among lactatingwomen is recommended.

Both government and private or-ganisations should develop infor-mation and communication strat-egies that would increase publicawareness and consciousness offortified foods especially thosewith SPS. It is also recommendedthat modification of the diet tofoods rich in vitamin A among in-fants, preschool children andwomen of reproductive age aswell as promotion of breast-feed-ing be pursued vigorously at thelocal government level. There-fore, capacity-building efforts forlocal government nutrition work-ers should continue.

If political will to implement nutri-tion policy, plans and programs

and legislative support continueto the next decade, virtual elimi-nation of VAD is not far behind.

References

1. Food and Nutrition Research Insti-tute. 2nd National Nutrition Survey:Philippines, 1982. Food and NutritionResearch Institute, Taguig, MetroManila, Philippines, 1984

2. Tanchoco CC, Cilindro P, Pingol M,Magbitang JA, Mendoza S, Flores E,Velandria F. 3rd National NutritionSurvey: Philippines, 1987. Part B An-thropometric and Clinical Survey.Food and Nutrition Research Insti-tute, Taguig, Metro Manila, Philip-pines, 1989

3. Valendria FV, Magbitang JA,Tanchoco CC, Mendoza TS, OrenseCL, Tangco JB, Mendoza SM,Duante CA, dela Cruz EO, Abarra LV.4th National Nutrition Survey: Phil-ippines, 1993. Part C. Clinical Nutri-tion Survey. Food and Nutrition Re-search Institute, Taguig, Metro Ma-nila, Philippines, 1995

4. World Health Organization. Globalprevalence of vitamin A deficiency.Micronutrient Deficiency InformationSystem (MDIS). Paper number 2.WHO/NUT/95.3. WHO, Geneva,1995

5. MI/UNICEF/Tulane. Progress inControlling Vitamin A Deficiency. Areport by MI, UNICEF and TulaneUniversity, 1998

6. Madriaga JR, Cheong RL,Desnacido JA, Marcos JM, CabreraIZ, Perals LA. Prevalence of vitaminA deficiency among specific Filipinopopulation groups. Philippine Jour-nal of Nutrition, 2001, 48: 29-43

7. Food and Nutrition Research Insti-tute. Philippine Nutrition Facts andFigures. Food and Nutrition Re-search Institute, Taguig, Metro Ma-nila, Philippines, 2001

8. Villavieja G, Cerdeña C, Molano W,Laña R, Boquecosa J, Raymundo B,Nones C, Abaya H, Palafox E,Chavez M, Burayag G, Pine C,Recuenco J, Saturno D, de losReyes C. 4th National Nutrition Sur-vey: Philippines, 1993. Part A. FoodConsumption Survey. Food and Nu-trition Research Institute, Taguig,Metro Manila, Philippines, 1995


9. Villavieja GM, Palafox EF, CerdeñaCM, Laña RD, de los Reyes CM,Shekar M. Maternal night blindnessas an indicator of vitamin A deficiencyin the Philippines. Philippine Journalof Nutrition, 2001, 48: 103-16

10. Local Government Code, 1st ed.Central Law Book Publishing,Quezon City, Philippines, 1992

11. Solon FS. Short Course Training inVitamin A and Nutrition. SIGHT ANDLIFE Newsletter 1/2001

12. Solon FS, Solon MS, Mehansho H,West KP, Sarol J, Perfecto C, NanoT, Sanchez L, Isleta M, WasanwitsutE, Sommer A. Evaluation of the ef-fect of vitamin A-fortified margarineon the vitamin A status of preschool

Filipino children. European Journalof Clinical Nutrition 1996, 50: 720-23

13. Villavieja GM, Sario IS, Laña RD,Cerdeña CM, Tarrayo ER, NonesCA. Awareness and usage of forti-fied foods in the Philippines. Philip-pine Journal of Nutrition 2001, 48:147-62


Successful vitamin A supplementationin NicaraguaJosé O. Mora1 and Josefina Bonilla2, MOST, the USAID Micronutrient Program

IntroductionEven though clinically evident vi-tamin A deficiency (VAD) has notbeen identified as a significantpublic health problem in LatinAmerica, sub-clinical VAD in chil-dren under 5 years of age (se-rum retinol <20 µg/dl) has beenfound to be a serious problem ina number of countries. In the late1990s, the regional prevalence ofsub-clinical VAD from nationalsurveys amounted to about 25%in children (1). Estimated nationalprevalence rates in three coun-tries exceeded the regional av-erage: El Salvador (36%), Nica-ragua (31%) and Peru (30%).High VAD prevalence in CentralAmerican countries was foundsince the mid-1960s, but it wasnot until the mid-to-late 1970sthat some governments formallyrecognised VAD as a seriouspublic health problem and beganto address it. Universal or tar-geted supplementation, usuallylinked to immunisations (2), wasadopted as a short-term re-sponse for at least a temporaryimprovement in vitamin A statuswhile long-term interventions(e.g. food fortification) were im-plemented. The greatest advan-tage of adding vitamin A distribu-tion to immunisation campaignsis that the additional cost is small,whereas the impact on child sur-vival can be significant.

A recent review by the PanAmerican Health Organization(PAHO) documented achieve-ments in ten Latin Americancountries where vitamin A supple-mentation was incorporated intoimmunisation activities, with in-creased involvement of humanresources from regular healthprograms and growing interest instrengthening implementationthrough integrated efforts andregular monitoring (PAHO, 2001).Despite some progress, by 2001only five countries had country-wide programs, and a number ofprogrammatic constraints pre-cluded achievement of consist-ently high coverage among chil-dren. Nicaragua, a small countrywith about 5 million inhabitants(about 800,000 children under 5years of age), has been an out-standing exception. This reportbriefly describes the positive ex-perience with vitamin A supple-mentation in Nicaragua utilisingan effective strategy that is likelyto succeed in other VAD coun-tries.

Nicaragua experi-ence with vitamin AsupplementationBackground

VAD was found a significantproblem in Nicaragua since themid-1960s but specific actionswere not taken then. In 1993 theNicaraguan Ministry of Health

(MOH), with USAID assistance,carried out a national study toassess the prevalence of sub-clinical VAD in children and ofanemia in women and children,and to estimate family and indi-vidual food consumption. Thestudy revealed that about 60% ofthe children 12–59 months of ageand 70% of the families con-sumed less than the recom-mended amounts of vitamin A perday, and 31% of the children hadsub-clinical VAD. With these find-ings, the MOH nutrition groupengaged in creating awarenesson the health and developmentimplications of micronutrient de-ficiencies, including the serious-ness of VAD and the need to act.Sensitisation efforts targeted alllevels of the public and privatesector, academic institutions,politicians and the general popu-lation. This resulted in strong po-litical commitment to addressVAD as a priority problem.

Supplementation throughNational Health Campaigns(NHCs)

After contemplating different op-tions, the MOH adopted supple-mentation as an emergency andtemporary measure to controlVAD while universal fortificationof a staple food could be estab-lished3. Vitamin A supplementswere officially included in theMOH list of essential medicines.A vertical supplementation pro-gram for vitamin A alone was not

1. Technical Advisor2. Nicaragua Resident Advisor


seen warranted. The challengewas to secure high coverage ofchildren 6–59 months twice ayear. Despite some initial con-cerns about sustainability of theapproach, it was decided that in-corporation of vitamin A supple-mentation into the very success-ful National Immunisation Cam-paigns (NICs, “Jornadas Nacion-ales de Vacunación”) offered thebest programmatic option.

NICs, carried out four times peryear in the 1980s, were reducedto three times in the early 1990s.In order to secure high coveragetwice per year, the scope of theNICs was expanded into an inte-grated package of preventivemother/child primary healthcareservices to be implemented twice(rather than three times) per year.In addition to distribution of vita-min A and iron/folate supple-ments, the package includes rou-tine immunisations, anti-hel-minthics medications, health edu-cation, oral rehydration salts,contraceptives, chloride for wa-ter treatment, and anti-lousemedications. Therefore, twice ayear National Health Campaigns– (NHCs, “Jornadas Nacionalesde Salud”), spearheaded by im-munisations, substituted for theNICs. This required establishinga semi-annual cycle of districtactivities improving facility usagefor preventive services, as wellas community outreach usingschools and households of com-munity leaders and/or “briga-distas” as delivery posts. Thepolicy decision was made earlyin 1994 and later formalised in the5-year National MicronutrientPlan 1996–2000. Technicalguidelines were developed for

the services to be provided, in-cluding vitamin A supplementa-tion targeted to children and post-partum women following WHOrecommendations.

Under the MOH decentralisationprocess, the health sector inNicaragua encompasses 17 Dis-tricts or Integrated Local HealthSystems (“Sistemas Locales deAtención Integral en Salud,SILAIS”) which enjoy high man-agement and budgetary au-tonomy. MOH central units pro-vide technical guidance, trainingand supervision to districts. Im-plementation of the NHCs is aresponsibility of the districts.MOH central units are responsi-ble for setting the stage for coor-dinating and supporting NHCsimplementation twice per year (inMay and October) by securingsufficient supplies and providingtraining as needed to the districtsand these, in turn, to the localhealth services. Media commu-nications support is also providedto districts to timely sensitise andmobilise communities, and toenlist the long established largecadre of community volunteers(“brigadistas”) in support of theNHCs.

During the NHCs, communities(particularly women and children)are massively mobilised by en-gaging media, municipal authori-ties, the church and other com-munity groups, with very activeparticipation of primary schoolteachers, secondary school anduniversity health science stu-dents, community volunteers, tra-ditional birth attendants, the mili-tary and non governmental or-ganisations (NGOs). The need totake advantage of the variety ofprimary healthcare services pro-vided at local health facilities is

emphasised. Each NHC maytake one week in urban areasand as many as four weeks inrural isolated areas where this ispractically the only opportunity forpeople’s contact with the publichealth system.

Vitamin A supplementation is onlyone, albeit a very important one,of the services provided. It is tar-geted to children 6–59 monthsand post-partum women, al-though the latter are not coveredby the NHCs. While most immu-nisation coverage is achieved inthe first round of the year, thesecond round provides an oppor-tunity for booster doses and forreaching children not covered inthe first round with the full set ofprimary healthcare services.Each campaign is carefullyplanned jointly by the centralMOH and the districts, andfunded almost entirely from regu-lar budgetary allocations. Up to1998, the MOH procured vitaminA supplements using its own re-sources. Since then, supple-ments have been mostly donatedby the Canadian governmentthrough the Micronutrient Initia-tive (MI), UNICEF, Wisconsin Li-on’s Club, and the JapaneseGovernment, in response to spe-cific requests based on estimatedneeds prepared by the districts.In order to increase the coverageachieved through the NHCs, thedistricts are encouraged to tapany ongoing opportunities forcontacts with mothers and chil-dren to ensure additional supple-ment delivery through routinehealth services.

A simple but effective supervisionand monitoring system has beenestablished which, in addition tooversee implementation, periodi-cally provides information on

3.Universal fortification of sugar withvitamin A formally began in 2000.


population coverage achieved byeach district through both NHCsand additional routine distribu-tion. Supplement delivery is reg-istered on each child’s healthcard and recorded on immunisa-tion tally sheets that are monthlycompiled at health units and sub-mitted to the district offices, andthese, in turn, to the appropriateMOH central units. The Ex-panded Program of Immunisa-tions (EPI) and the Departmentof Statistics enter and processthe information to produce amonthly immunisation and vita-min A coverage report that is con-solidated every six months.Semi-annual reports, with cover-age rates by age group and dis-trict, are distributed and dis-cussed at the central and districtlevel in post-campaign evaluationmeetings where the relative cov-erage ranking of each district isexamined and options for im-provement discussed. Public andprofessional recognition encour-ages health staff to achieve highrates of coverage.

Population coverage

Vitamin A supplementation cov-erage rates for children 6–59months of age from 1994 to 2001,by year and round, are shown inFigure 1. Coverage has gradu-ally increased in both roundssince 1994 and levels higher than70% have been sustained since1999, with levels above 80% inthe last two years. The averagecoverage rate by round from1997 to 2001 amounted to 79%in first rounds and 78% in sec-ond rounds. The latter is a re-markable achievement, as get-ting high second-round coveragerates has been a formidable chal-lenge for many countries. Only 1–2% of the total coverage hasbeen achieved through non-NHCroutine health service distribu-tion.

Biological impact

The ultimate biological impact ofvitamin A supplementation wouldbe expected as changes in se-

rum retinol levels and, eventually,in infant and child mortality rates.A 2000 National MicronutrientSurvey carried out about fourmonths after the second NHC of1999, with USAID/MOST techni-cal and financial support, re-vealed a dramatic reduction(72%) in the prevalence of vita-min A deficiency (VAD) in children12–59 months of age, from31.1% in 1993 to 8.6% in 2000(Figure 2). This significant im-provement may be mostly attrib-uted to the cumulative effect ofvitamin A supplementation, as aresult of the consistently highcoverage rates in children overthe six-year period preceding thesurvey, given the absence ofother specific interventions in thesame period. Successive roundsof supplementation may havegradually increased serum retinollevels over time. According toconventional knowledge, most ofthe effect of a large dose of vita-min A on serum retinol of childrenis expected to vanish after 3–4months (6-7); however, studieson the long-term cumulative im-pact of repeated supplementa-tion rounds have not been re-ported.

Alternative explanations, e.g. sig-nificant changes in the socio-eco-nomic conditions of the popula-tion and the possible impact ofsugar fortification may be reason-ably ruled out, as no evidenceexists of improved social andeconomic conditions during theinterim period and by the time ofthe survey in early 2000 the sugarfortification program was juststarting. As shown in other coun-tries where sugar consumption ispractically universal, fortificationwould be expected to have a sig-nificant mid- to long-term impacton the vitamin A status of the

1994

51 51 50

20

78

70

64 65

82

72

9491

87

80

50

62

1995 1996 1997 1998 1999 2000 2001

% c

ove

rag

e

100

80

60

40

20

0

first round

second round

Source: Ministry of Health, Nicaragua EPI and Department of Statistics

Figure 1. Coverage of vitamin A supplementation in children 6-59 monthsold, Nicaragua 1994-2001.


population. Once fortification isfully established, supplementa-tion may need to be targeted onlyto the youngest children (e.g.under two years) who are lesslikely to benefit from fortificationbecause of their low sugar intake.

Based on the results of experi-mental studies (8), a reduction ininfant and/or child mortality wouldbe expected as the ultimate bio-logical impact of supplementa-tion, particularly in countries withserious VAD and high levels ofchild mortality. Interpretingchanges in infant/child mortalityrates estimated from nationalsurveys is complicated by meth-odological problems in estimat-ing mortality rates and by themany interrelated factors thatmay influence child mortality infree living populations. Attributionof eventual changes to specificfactors is particularly difficult indeveloping countries with a secu-lar trend towards consistent de-cline in mortality rates. Recenttrends in estimated infant andchild mortality rates in Nicaragua(9) for five-year periods from1973/78 to 1993/98 are shown inFigure 3. Both infant and childmortality consistently declined by60–63% in the 20-year period(about 3% per year). There wasa downward trend in the rates ofdecline by 5-year periods up to1988–1993, e.g. from 30–33%(about 6% per year) between1973–1978 and 1978–1983 to 4–9% (less than 1-2% per year)between 1983/88 and 1988/93.However, this trend reversed(back to higher rates: 20–22%,about 4% per year) in the period1988/93 to 1993/98. Interestingly,this acceleration in the rate ofmortality decline coincides withthe implementation of vitamin Asupplementation and, although

there might be several potentialexplanations for such finding, asignificant contribution of vitaminA supplementation seems highlyplausible.

Key elements forsuccess

A number of factors have beenkey to successful implementationof vitamin A supplementation inNicaragua:• Effective sensitisation at all lev-

els of society, the health sys-tem and the community to gen-erate awareness of vitamin Adeficiency as a priority prob-lem.

• Strong government politicalcommitment expressed inpolicy and budgetary decisionsand technical guidelines.

• Integration of the supplemen-tation strategy into ongoingnutrition and health activities.

• Well trained and motivatedstaff who have the necessaryknowledge and skills.

• Program ownership by healthdistricts and local units.

• Skilled management of pro-grams and timely supply ofsupplements.

• Building on a strong health in-frastructure and communitysupport.

• A supervision and monitoringsystem providing timely feed-back to health services.

• Effective communication andbehaviour change strategies.

ConclusionsNicaragua provides a successfulexample of periodic, active, insti-tutionalised, integrated distribu-tion of vitamin A supplementswith consistently high coverage.Integrating supplementation aspart of a package of basic healthservices to be delivered twice ayear through National HealthCampaigns, Weeks or Days is aviable, affordable and effectiveoption to facilitate achievement ofconsistently high coverage rates,and is more likely to be widelyaccepted and endorsed by healthauthorities than specific cam-paigns for vitamin A distributionalone. As national immunisation

1993

31.1

8.6

2000

% p

reva

len

ce

40

30

20

10

0

Figure 2. Prevalence (%) of vitamin A deficiency (serum retinol < 20 µg/dl)in children 12-59 months old, Nicaragua, 1993 and 2000.


days (NIDs) are scaled down orphased out in many countries,NHCs offer an effective alterna-tive strategy to sustain the deliv-ery of vitamin A to young childrenat the high coverage ratesneeded to realise its full poten-tial to reduce mortality. Twiceyearly delivery of vitamin A sup-plements through synchronisedNHC distribution yields excellentresults, as shown in Nicaragua.Vitamin A supplementation canbe made a key component of anintegrated package of preventiveservices designed to improvechild survival by establishing asemi-annual cycle of district ac-tivities designed to improve facil-ity usage for preventive services,thus high coverage of several keychild survival interventions canbe achieved all together.

The NHCs can be complementedby routine healthcare services toincrease coverage, maintain staffmotivation and strengthen long-term sustainability. All routinehealth service contacts offer op-portunities to increase coveragewith vitamin A supplements (post-natal clinic visits, immunisation,growth promotion, other Motherand Child Health clinic contacts,and sick child attendance). Al-though, in principle, integration ofsupplementation within regularhealth services is a desirablegoal, particularly when the cam-paign approach is not feasible,this strategy alone has notproved effective in reaching con-sistently high coverage rates.Moreover, health facility attend-ance for preventive services tendto drastically decline for olderchildren, making it difficult toachieve adequate coverage ofpreschool children. However, itoffers a sound opportunity to en-hance the coverage attained

1973/78

30%

21%

20%

4%

9%

22%

25%

33%

1978/83 1983/88 1988/93 1993/98

Death

rate

x 1

000 liv

e b

irth

s

100

80

60

40

20

0

infant mortality

child mortality

Figure 3. Trends in infant and child mortality, Nicaragua, 1973-1998 (source:Nicaragua Demographic and Health Survey 1998). Percent figures are ratesof decline from previous period.

through NHCs and would in-crease the long-term sus-tainability of vitamin A supple-mentation.

References

1. Mora JO, Gueri M, Mora OL. VitaminA deficiency in Latin America and theCaribbean: An overview. Pan Am JPublic Health 1998, 4(3): 178-86

2. WHO/UNICEF. Integration of vitaminA supplementation with immuniza-tions: policy and programme implica-tions. Report of a meeting, 12–13January 1998, UNICEF New York.World Health Organization, Geneva,1998

3. PAHO. Integrated vision for vitamin Asupplementation in the Americas.Regional meeting report, 2–4 May2001. Managua, Nicaragua. Pan AmHealth Org HPP/HPN/MN/49-17.Washington, DC, 2001

4. MINSA/Nicaragua. Encuestanacional sobre deficiencia demicronutrientes en Nicaragua, 1993.Informe final. Ministerio de Salud,Managua, Nicaragua, 1994

5. MINSA/Nicaragua. Plan nacional demicronutrientes: Nicaragua, 1996–2000. Ministerio de Salud, Managua,Nicaragua, 1994

6. West KP Jr, Sommer A. Periodic,large oral doses of vitamin A for theprevention of vitamin A deficiency andxerophthalmia: a summary of experi-ences. The Nutrition Foundation Inc,Washington, DC, 1984

7. Flores H, Campos F, Araujo CRC,Underwood B. Assessment of mar-ginal vitamin A deficiency in Brazilianchildren using the relative dose re-sponse procedure. Am J Clin Nutr1984, 40: 1281-1289

8. Beaton GH, Martorell R, L’Abbe KAet al. Effectiveness of vitamin A sup-plementation in the control of youngchild morbidity and mortality in devel-oping countries. Final report to CIDA.University of Toronto, Canada 1992

9. INEC/MINSA/DHS. Encuestanicaraguense de demografía y salud,1998. Instituto Nacional deEstadística y Censos, INEC,Ministerio de Salud, MINSA, MacroInternational Inc. Managua, Nicara-gua, 1999


Vitamin A deficiency in Micronesia*Frits van der Haar, Emory University, Dept. of International Health, Atlanta, GA, USA

On 8–11 May 2002 in New York,the United Nations General As-sembly held a Special Sessionfor Children to review progressmade since the World Summit forChildren in 1990. The report bythe UN Secretary-General MrKofi Annan, entitled “We the Chil-dren” (1), shows the significantprogress made in the 1990s inlarge-scale vitamin A capsule dis-tribution, which is estimated tohave prevented 1 million childdeaths between 1998 and 2000alone. The report, however, alsopoints to significant challengesahead in continued distributioncampaigns and it indicates thatinitiatives aimed at fortified foodwill be essential.

While in New York, Heads ofState and Government weresigning off on a vision and spe-cific goals for social and eco-nomic development in the newMillennium (2), including the sus-tainable elimination of vitamin Adeficiency (VAD) by 2010. Cor-rection of the severe VAD prob-lems in the Federated States ofMicronesia (FSM) should receivehigh attention among the priori-ties following the renewed globalcommitment.

A clinic-based study in 1987 inChuuk, one of four FSM states,found evidence of abnormal vi-tamin A status by conjunctivalimpression cytology among half

of the 36–83 months old childrenattending the out-patient clinic(3). This initial exploration wasfollowed by a state-wide study in1988–89, resulting in similar find-ings (4). Then in 1992 in a studyof children aged 18–24 monthsand 3–6 years, over 50% of the

children were found to have VADas defined by a serum retinol ≤0.70 µmol/l (20 µg/dl) (5). Simi-lar results were found in a com-munity-based study in Pohnpeiwith 362 children 24-47 monthsof age (6). In response, the FSMhealth service started periodic

0.3

0.2

0.1

0

0 0.35 0.70

Re

lati

ve

fre

qu

en

cy

1.05 1.40 1.75

Serum retinol (µmol/l)

Chuuk

Pohnpei

Yap

Kosrae

NHANES

Figure 1. Serum retinol distribution.

A view of Pohnpei island with the area of the city centre of Kolonia.

* see also article by Lois Englbergerin the SIGHT AND LIFE Newsletter2/2002, pages 28-32


vitamin A supplementationamong children up to 12 years ofage in Chuuk and PohnpeiStates.

Prior to extending the supple-ment policy nationwide, the FSMDepartment of Health, assistedby UNICEF and the Center forDisease Control, Atlanta, (CDC),surveyed the VAD situationamong young children in Yap andKosrae, the remaining two FSMstates. Proportionate-to-popula-tion random sample surveyswere carried out during Januaryand February 2000 among 218and 267 children aged 24–59months in Yap and Kosrae, re-spectively. Body height andweight were measured to esti-mate wasting and stunting, usingWHO/CDC references (Z-scores< -2 SD below the reference me-dian). Venous blood was drawnfor HemoCue estimation of hae-moglobin, and the serum sepa-rated for retinol analysis at CDCby HPLC. The mean serum reti-nol was 0.712 µmol/l (95% C.I.:0.691, 0.737); 0.628 µmol/l inKosrae and 0.799 µmol/l in Yap(p<0.001), respectively. VADamong children was 48.8%, witha higher (p<0.001) prevalence inKosrae (63.3%) than Yap(33.8%) (7).

The retinol frequency distribu-tions found of FSM children arecompared in Figure 1 with theserum retinols among 48–71months old, apparently healthyUS children (NHANES III, 1988–94). Although the respective lo-cations on the serum retinol scalediffer somewhat, all the distribu-tions among FSM children showa marked downward shift com-pared to US children, illustratingan associated risk of morbidityand mortality among the FSM

child populations (8). The preva-lence of wasting (3.8%), stunting(16.6%) and anaemia (11.2%)among children aged 2–4 yearsin Kosrae and Yap did not differsignificantly between the twoStates, nor were they much dif-ferent from prevalences reportedamong children of Chuuk andPohnpei in 1992–93. In contrastto cross-sectional surveys inother countries with severe vita-min A deficiency (9,10) the poorvitamin A status in FSM childrendoes not co-occur with similarhigh prevalences of other malnu-trition indicators.

As already instituted for childrenof Chuuk and Pohnpei, universalvitamin A capsule distribution 2–3 times annually is a most practi-cal response for the children ofYap and Kosrae. However, inview of the scale and common-ness of VAD in each State amongthe young children – the mostvulnerable group often used asproxy for the whole population –a more comprehensive approachmay be indicated for FSM to ad-dress the widespread problem.Fine-tuned to local conditions ineach State, a national policyshould devise a thoughtful com-bination of public health meas-ures, promotion of more nutri-tious diets – including local vita-min A-rich foods – for all agegroups, and vitamin A fortificationof commonly eaten foods, tocomplement the ongoing capsuledistribution among young chil-dren.

References1. Annan KA. We the Children. Meeting

the promises of the World Summit forChildren. New York, UNICEF, 2001.Accessible at http://www.unicef.org/specialsession/

2. A World Fit for Children. Draft out-come document of the PreparatoryCommittee for the Special Session ofthe General Assembly on Children.New York, United Nations, 2001. Ac-cessible at http://www.unicef.org/specialsession/

3. Lloyd-Puryear MA, Humphrey JH,West KP Jr, Aniol K, Mahoney J,Keenum DG. Vitamin A deficiency andanemia among Micronesian children.Nutr Res 1989, 9: 1007-1016

4. Lloyd-Puryear MA, Mahoney J,Humphrey JH, Mahoney F, Siren N,Moorman C, West KP Jr. Xerophthal-mia, vitamin A deficiency in Micro-nesia: A statewide survey in Chuuk.Nutr Res 1991, 11: 1101-1110

5. Mahoney F. Hepatitis B vaccinationprogram and vitamin A deficiency inChuuk. Weno, Chuuk: Center for Dis-ease Control and Prevention, andChuuk State Department of HealthServices, 1992

6. Auerbach S. Report of Pohnpei ChildHealth Survey. Findings presented tothe Federated States of Micronesiaand Pohnpei State Department ofHealth Services. Palikir, Pohnpei: USPublic Health Service and FSM De-partment of Health Services, 1994

7. Centers for Disease Control and Pre-vention. Vitamin A deficiency amongchildren – Federated States of Micro-nesia, 2000. MMWR 2001, 50(24):509-512

8. Humphrey JH, West KP, Sommer A.Vitamin A deficiency and attributablemortality among under-5-year-olds.Bull WHO 1992, 70: 225-232

9. Bloem M. Interdependence of vitaminA and iron. An important associationfor programmes of anaemia control.Proc Nutr Soc 1995, 54: 501-508

10.Sommer A, West KP. Vitamin A Defi-ciency: Health, survival and vision.New York, Oxford University Press1996, pp 150–188


The contribution of the “carotenoid world”George Britton, University of Liverpool, School of Biological Sciences, Liverpool, UK*

In a way it feels strange to findmyself among all the other cor-respondents, most of whom havedevoted their entire working livesto the cause of fighting vitamin Adeficiency. I have come to it lateafter years of working in the fieldof carotenoid chemistry and bio-chemistry. My interest in the prob-lem of vitamin A deficiency waskindled by Delia Rodriguez-Amaya during some highly enjoy-able visits to Brazil. Then, like somany others, I came under theinfluence of the vision and inspi-ration of Jim Olson during timewe spent together at the Latin-American Congress on FoodCarotenoids organised by Deliain Campinas in 1998. This led meto my first, and so far only, IVACGmeeting in Durban in 1999,where I had the privilege of tak-ing part in Jim’s wonderful littlespecial interest workshop on pro-vitamin A carotenoids in food.

In this first encounter with theworld of vitamin A deficiency(VAD), my immediate impressionwas of two strongly held andforcefully promoted views. Onegroup of people felt strongly thatincreasing the intake of provita-min A carotenoids from food canmake a major contribution to im-proving vitamin A sufficiency inpopulations, whereas anothergroup believed that this approachcan never be effective; the onlyeffective solution lies in supple-mentation or fortification with vi-tamin A or even β-carotene. Withthe benefit of inexperience, it waseasy to take the simple view thatany and every approach that cancontribute to improving the vita-min A status of an individual or apopulation is valuable and shouldbe used. Since then neither timenor thought nor reading nor dis-cussion have changed this view.It seems logical that the basic

vitamin A status of a populationcan be maintained and improvedby increasing consumption ofβ-carotene-containing vegeta-bles and fruit, with supplementa-tion and fortification then beingused when required, to give arapid improvement in populationsseen to be at risk.

In addition to this, in the West, adiet rich in fruit and vegetables isrecommended because it pro-vides many other vitamins andmicronutrients, and is associatedwith reduced risk of cancer, heartdisease and other degenerativediseases, as well as maintenanceand stimulation of the immunesystem. Surely everyone de-serves the benefits that in-creased consumption of fruit andvegetables would bring.

Can the carotenoid world andcarotenoid research make a

* e-mail: [email protected]. See also: www.carotenoidsociety.orgThe photographs of animals and plants coloured through carotenoids were given by courtesy ofMr Jonathan Taylor, Roche Vitamins, Basel.

Scarlet ibis Poppies


practical contribution to the fightagainst vitamin A deficiency? Theexpertise that is available for theanalysis of carotenoids has beenused and could be used in anumber of ways. Possibilities in-clude (i) Helping to optimise andstandardise analytical methodsfor general use; (ii) Establishinga “pyramid structure” with simplequantitative analysis in the fieldas the base and progressingthrough local or regional analyti-cal centres to national or interna-tional centres where sophisti-cated equipment is available andcomplex problems, includingstructure elucidation, can besolved; (iii) Using this to compilea comprehensive data base ofcarotenoid occurrence and con-centrations in local plants in allregions. This would have possi-

ble benefits in two directions, firstby identifying new provitamin Asources (new species, varieties)in relation to the fight again VADand second by revealing poten-tial sources for commercial pro-duction that would increase gen-eral commercial activity andstandard of living through localenterprises; (iv) Providing a soundanalytical basis for selecting thebest varieties for cultivation, evalu-ating growth conditions for opti-mum yield and carotenoid con-tent, and for determining and un-derstanding the effects of storing,processing and cooking on caro-tenoid stability and bioavailability.

In pursuing this work, we must bereasonable and realistic aboutwhat is actually needed and use-ful. With the HPLC methods now

available, it is easy to obtain veryprecise data for the carotenoidcontent and composition offoods. The practical value of theprecise figures is questionable,however. The numerical valuescome from the analysis of par-ticular samples of a given vari-ety, collected in one place, hav-ing been grown under unspeci-fied or optimised conditions andstored in some way for an un-specified time. Tabulated datashould be seen as a useful indi-cator of what may or may not begood sources of carotene, but itcannot be assumed that the fig-ures given are even close tothose for a real food sample pro-duced under often difficult localconditions. This emphasises theneed for carotenoid researchersto be aware that not only environ-mental and climatic conditions butalso local traditions, customs andculture must be taken into accountwhen trying to find practical solu-tions. There is no substitute forexperience in the field. With thisin mind, it would be particularlyuseful, for example, to develop asimple method to give a rapid,reliable and sufficiently preciseindication of provitamin A carotenecontent of the food materials thatare actually being consumed.

MushroomStick insects

Striped bug Butterfly


It will also be very beneficial ifcarotenoid researchers can beencouraged to keep VAD inmind when evaluating othercarotenoid studies, and to ex-tract from the mass of dataavailable the information thatis really useful and relevant inthe context of VAD. People whoare working in the field and try-ing to encourage increased pro-duction and consumption of pro-vitamin A carotenoids, for exam-ple via cottage gardens, are notgoing to read the primary litera-ture or assimilate details of ana-

lytical procedures and tables ofprecise figures. They should beable to rely on “experts” to dothis for them in an unbiased wayand then to give them guidancethat they can act upon in prac-tice.

Sadly, apart from visionariessuch as Jim Olson, few carote-noid researchers outside the re-gions affected have given morethan a passing thought to theglobal problem of vitamin A defi-ciency. As the carotenoid fieldhas diversified, new aspectshave aroused public interest,been seen as exciting and chal-lenging, and generated commer-cial activity, especially in re-sponse to the ever-increasingreports that carotenoids mayhave many health benefits. Asfar as VAD is concerned, a typi-cal view might be that “It is wellknown that β-carotene is a ma-jor dietary source of vitamin A, itis converted into vitamin A bycleavage, it is present in fruit andvegetables, and it is easy to de-termine precisely how much ispresent in the various sources.We know the answers; it’s up tothem to get on with it. We’ve gotmore interesting and challengingproblems to tackle”.

Can this attitude be changed? Ihope so and I believe so, and Iwould like to think that a key rolecan be played in this by the rela-tively newly formed InternationalCarotenoid Society, of which Ihad the honour to be the firstPresident. The InternationalCarotenoid Society was estab-lished to fill the need for a focusfor research, education and otheractivities in the broad carotenoidfield and, especially, to provide aforum for contact and communi-cation between carotenoid re-searchers from different disci-

Brazilian tanager

Poison arrow frog Starfish

Redheaded blackbird


plines and with complementaryexpertise, and from different partsof the world. A major aspect ofthis which is now being promotedstrongly, is the establishment ofregional branches of the Society,to encourage contact and inter-action between people in the re-gion with interest in carotenoids,and to stimulate communicationbetween workers from differentregions who have similar inter-ests, so that all can benefit fromdialogue and progress. Brancheshave been set up, or are beingset up, in Latin-America (contactperson Delia Rodriguez-Amaya,UNICAMP, Brazil), South-EastAsia and the Pacific (contact per-son Pongtorn Sungpuag,Mahidol University, Thailand),and the SAARC countries of theIndian sub-continent (contactperson Umesh Goswami,Gauhati University, India). We areopen to approaches from caro-tenoid researchers in other re-gions, to explore the possibilityof additional branches or alli-ances.

Regional meetings, such as theLatin-American Congress andthe South-East Asia and PacificRegional Meeting have brought

been very successful catalystsfor the foundation of regionalbranches and activities. Practicalworkshops have proved particu-larly useful; more are projectedin the near future.

The International Carotenoid So-ciety as a whole and through itsbranch activities will not ignorethe problem of VAD. I will be verypleased to hear at any time fromanyone who has questions aboutcarotenoids and the Society,ideas for activities or suggestionsof how the ‘carotenoid world’could get involved and contributeto the valuable work that is beingdone in the fight against VAD.

together many interested peoplefrom all over the region and have

Flamingos

Coltsfoot


Carotenes as dietary precursors of vitamin A:their past and their future*Noel W. Solomons, MD, Scientific Coordinator, Center for Studies of Sensory Impair-ment, Aging and Metabolism (CeSSIAM), Guatemala City, Guatemala

James Allen Olson became aguiding light of the CarotenoidResearch Interaction Group(CARIG). Hence, it is more thanappropriate that the CARIGshould institute a permanentmemorial in his name on theacademic platform of Experi-mental Biology. As for me, as aprofessional, and for the Centerfor Studies of Sensory Impair-ment, Aging and Metabolism(CeSSIAM) in Guatemala, wewere attracted to CARIG not be-cause of the emerging issues ofcarotenoids as prophylaxis forchronic diseases, but rather be-cause of their role as precursorsof vitamin A. This was also a con-cern of Jim Olson, and it is a spe-cial honour to be invited to givethe first James Allen Olson Me-morial Perspectives on Carot-enoids, lecture.

Jim Olson was a special spirit. Inan obituary article I published inthe European Journal of ClinicalNutrition after his untimely deathin September 2000, I wrote,“James Allen Olson was a uniquegiant – a gentle giant – in ournutrition community. His interests

bridged and spanned the chem-istry, biology and public healthinterests of both retinoids andcarotenoids, dominated both top-ics, and assumed leadership.”(1). In this spirit of dual concern,Jim Olson created a cocktail re-ception called VARIG (Vitamin AResearch Interaction Group) atFASEB, and eventually this hasmerged to the CARIG-VARIG re-ception, mingling those whoseprimary professional concernwas retinoids with those with acarotenoid bent.

Finally, Present Knowledge inNutrition, published by the ILSIPress, is perhaps the secondmost important of the compre-hensive general-nutrition text-books. Last year, I completed thetask requested of me by yet an-other founding father of CARIG,Rob Russell. As co-editor of thePresent Knowledge in Nutrition,VIII, he invited me to write thechapter on “Vitamin A andCarotenoids” (2). This was thefirst time that the chapter hadcombined both entities under oneroof, and Jim Olson had been theperennial author of the vitamin A

chapter for this textbook. Afterproclaiming my unworthiness forthe task, I was convinced by DrRussell to undertake it, but wasconfronted with an organisationalquandary. How do I separate andstreamline the discussion ofcarotenoids as provitamin A pre-cursors of retinoids and that ofintact, absorbed carotenoids asbioactive agents? I may not havegotten it right, but once again Iwas counselled by the simple, butprofound, distinction that waspromoted by Jim Olson with re-gard to food constituents, that offunctions and actions. Functionsare: “an essential role played bythe nutrient in growth, develop-ment, and maturation.” Actionsare: “demonstrable effects in vari-ous biologic systems that may ormay not have general physiologicsignificance.” (3). Here, we aregoing to be talking about function.

What is past is pro-logue

The chemical identificationof dietary vitamin A

The year of 1913 was a landmarkyear for vitamin A research, as itwas the date when the retinolform of the vitamin, a colourless,lipid-soluble compound, was dis-covered simultaneously in twolaboratories by McCollum andDavis (4) and by Osborne and

* This was presented in April in New Orleans in the mini-symposium oncarotenoids at the annual meeting of the American Society for NutritionalSciences at the Experimental Biology 2002 meeting as the first JamesAllen Olson Memorial Perspectives on Carotenoids Lecture, sponsoredby the Carotenoid Research Interaction Group (CARIG) of which Prof.Olson had been a motive force and founding member.


Mendel (5). In 1919, Steenbocksuggested a linkage between ayellow pigment in plants and theretinoid compound known as vi-tamin A. It was not until 1930 thattwo distinct investigators –Capper (6, 7) and Moore (8) –confirmed the existence of provi-tamin A activity in the carotenoidsof plants.

1965 was another key year astwo groups identified the 15-15'dioxygenase enzyme, which ap-parently introduced molecularoxygen into the centre of the sym-metrical β-carotene molecule toproduce two molecules of retinal(retinaldehyde) (9, 10). More re-cent insights include confirmationin vitro (11) and in vivo (12) thatthe conversion is typically stoi-chiometric. A diagrammatic rep-resentation of the chemicalscheme is shown in Figure 1 (13).The most recent advance, bring-ing us to the present, has beenthe cloning of the dioxygenase(14, 15). With this has come evi-dence of the regulation of thedioxygenation, consistent withany assumption of homeostaticmaintenance of total-body vita-min A status (13).

Eccentric cleavage to apo-carotenals by oxidation orenzymatic mechanisms can pro-duce retinoic acid (Figure 1). Anenzyme specific for 9,10 cleav-age by inserting molecular oxy-gen has been characterised (16,17). We must accept that the op-eration of this pathway must yielda maximum of one retinoid moi-ety for each parent molecule, butthat it must be regulated so asnot to produce any risk of exces-sive vitamin A accumulation.

For the two other common provi-tamin A moieties, α-carotene and

cryptoxanthin, and for minor con-tributors as well, we have littleknowledge of the bioconversionprocess. Once again, however,we must accept that the opera-tion of this pathway can yield onlya maximum of one vitamin A moi-ety from each provitamin A mol-ecule, and that it must be regu-lated so as not to produce anyrisk of excessive vitamin A accu-mulation.

The evolutionary signifi-cance of carotenoids forplants and animals

Most naturalists believe that pho-tosynthesis by the chloroplasts ofgreen plants is the single mostessential evolutionary landmark toallow for life as we know it onEarth for both the Plant Kingdomand the Animal Kingdom. It pro-duced a renewable origin andsource of calories, trapping theenergy of the sun into the foodchain. At the same time, it re-leased oxygen, which would allowfor efficient metabolism of energy.Solar radiation and oxygen, how-ever, were double-edged swords.They permit efficiency energytrapping in plants, but they stimu-late the formation of damagingfree-radicals and reactive oxygenspecies. Carotenoids are nature’ssunscreen, providing the anti-oxi-dant protection for photosynthesis.

All retinoids in nature and in thefood chain originally come fromplant carotenoids. Photosyn-thesizer (green) plants are au-tonomous and self-sufficient.Herbivores eat green plants(plant-based nutrients). Terres-trial carnivores generally eat her-bivores, whereas sharks (elas-mobranchs), higher marine fish,and marine mammals consumeother carnivores. Omnivores eat

plants, herbivores, carnivoresand other omnivores.

Humans are the classical omni-vores in evolution. The interest-ing question arises as to whetherhumans would adapt to the di-etary vitamin A problem in thespirit of an herbivore (i.e. a highlyefficient converter of plant precur-sors) or the spirit of a carnivore(i.e. largely dependent on pre-formed vitamin A).

Malnutrition and nutrientoverload as evolutionarydysadaptation

If we consider evolution to besynonymous with adaptation, wewould expect that evolutionwould always be tending towardsa situation in which the nutrientrequirements are adequately met– but not exceeded – by the ha-bitual diet. As such, in the equi-librium evolutionary state, nospecies should be subject tomalnutrition or nutrient overload.That is, by consuming enougheucalyptus leaves, and only eu-calyptus leaves, a koala shouldbe nutritionally replete; similarly,a queen bee should have all herenergy and micronutrient needssatisfied by an ad libitum diet ofroyal jelly and honey.

In nature, temporarily imbalancescan occur that put pressure onthe nutritional stability. Season-ality of food availability can pro-duce cyclical nutrient deficien-cies, but presumably this doesnot endanger the survival of aspecies. There can, however, bea prolonged scarcity of the tradi-tional dietary elements due toplagues among the foodspecie(s), competition for thefoods by other consumers in theecological niche, or overpopula-


tion by the index species, itself,leading to over-hunting or over-grazing. Alternatively, abruptchange can occur in the nutrientcomposition of food. These phe-nomena produce a kind of “fam-ine” situation which can be re-solved rapidly by recovery of thefood supply, or migration to ar-eas of richer sources. If neitherof these is an option, natural se-lection can proceed; those mem-bers of the herds with lower re-quirements will demonstrate in-creasing reproductive fitness,shifting the genetic pool towardlower requirements.

Similarly, a species in evolutionmight confront the situation of adrift of increasing nutrient concen-tration in their food(s) of choice,

leading to a situation of nutrientoverload bordering on toxicity.Again, genetic selection can fa-vour reproductive fitness amongthose with the higher tolerances,and lead eventually to a geneticshift to a population with toleranceto the new dietary levels.

For humans, cultural andtechnological advancestrump the natural evolu-tionary order

Following the aforementionedlogic, human diets should notproduce entrenched micronutri-ent deficiencies, but the exist-ence of xerophthalmia is evi-dence that they do. Anthropolo-gists and paleonutritionists as-sure us that the evolved tradi-

tional hunter-gatherers of prehis-tory were generally well-nour-ished (18, 19). The nutrient re-quirements of the evolvinghunter-gatherers were adaptedto their dietary selection when alltraditional foods were abundant,although seasonality effects werelikely. As humans evolved first tothe pastoralist and then to agrar-ian societies, distortions in dietaryselection disrupted the harmonyof their evolved nutrient require-ments (19). The micronutrient de-ficiencies we combat today are aconsequence of the agrarianrevolution, which produced pri-mary staples (plant foods such ascereal grains and tubers) of lownutrient density.

Figure 1. Overview of the main steps in vitamin A formation: Central cleavage at the 15,15’ carbon-carbon doublebond leads to two molecules of retinal, which subsequently can be reduced to retinol and stored as retinyl esters inthe liver or other tissues. As an alternative pathway the asymmetric cleavage pathway is shown on the right side.β-apo-carotenals of various lengths can be shortened through a series of β-oxidation-like steps to retinoic acid.


Humans cultural dysadap-tation can also producenutritional excess

On the other side of human nu-tritional imbalance is a propensityto have nutrient excess evolve inthe agricultural and technologicaleras. Obesity is an example ofexcess energy storage. Hypervi-taminosis A is the nutrient excessof relevance to this discussion.Preformed vitamin A (retinoids)can be toxic. Carnivores, espe-cially those at the top of the ma-rine food chain such as sharks,walruses, narwhals, and polarbears, are most resistant to anytoxic effects of retinoids. Omni-vores are intermediate in toler-ance, as a large percentage oftheir vitamin A can come fromplant sources. Herbivores aremost sensitive to retinoid toxic-ity, as preformed vitamin A isnever part of a plant-based diet.

A series of adverse conse-quences of excessiveexposure to vitamin A

With intakes of >500 mg of pre-formed retinyl esters, as occurredwhen European Arctic explorersconsumed liver of marine mam-mals, a severe and often fatalacute hypervitaminosis A syn-drome will result. With self-medi-cation or unwise prescription of7500 RE (retinol equivalent) pre-formed vitamin A daily, chronichypervitaminosis with neurologi-cal and hepatic consequencescan occur. Rothman et al. (20)have estimated that daily intakeof 3000 RE of retinol is sufficientto produce teratogenesis. Finally,the paradox of why the highestrates of osteoporosis are seen incountries with the highest percapita consumptions of calciumwas resolved in Sweden by the

suggestion that intake of the vi-tamin A in the calcium sources,milk, dairy products and fish,above the level of 1500 RE dailybegins to produce significantbone demineralization (21, 22).On the other side of the ledger,precursors of vitamin A(carotenoids) are regulatedhomeostatically in their conver-sion to vitamin A and cannot pro-duce hypervitaminosis A (23).

Rating the diet forits vitamin A con-tent:Conversion factors fordietary vitamin A

If one wants to know the totalamount of vitamin A available ina diet, one has to perform calcu-lations with certain assumptions.This was done by estimating thefoods consumed and assigninga value to the chemical constitu-ents of the foods. In foods of ani-mal origin the predominant formof vitamin A is the retinoid form(retinyl esters), although eggs,viscera, animal fat, and milk con-tain important amounts of provi-tamin A. Plant foods, have onlypigment sources, with thecarotenoids β-carotene, α-carot-ene, and β-cryptoxanthin beingthe most common members ofthis family with the capacity to beprecursors of vitamin A.

Retinol equivalents

Initially, dietary vitamin A was ex-pressed in terms of the weight ofthe compounds of interest infoodstuffs. This soon moved,however, to the expression of In-ternational Units (IU). The reali-sation that bioconversion of di-etary provitamin A carotenoids

was neither stoichiometric norequivalent across different chem-istries led to a rationalisation ofthe quantitative expression offood vitamin A value. In 1967, anexpert panel of the United Na-tions’ agencies devised a systembased on the retinol equivalent(24). By this convention, one REwas defined as equal to 1 µg ofall-trans-retinol, to 6 µg of all-trans-β-carotene, and to 12 µg ofother provitamin A carotenes. Atthe level of description of popu-lation nutrient consumption,these assumptions went withoutmajor challenge for 25 years.However, when it came to popu-lation action in the renewed pub-lic health battle against hypovi-taminosis A that arose from thefindings of Sommer and col-leagues (25), these conversionfactors began to receive scrutiny.

Critique of the assump-tions of retinol equivalencyof provitamin A sources

The 1967 retinol equivalents sys-tem has been used to interpret thevitamin A in the food supply. Theestimates from U.N. sources, re-produced by McLaren and Frigg(26) (Figure 2), are based on reti-nol equivalents. Common sensequestions begin to emerge whenone takes note of the small differ-ence in the daily vitamin A supplyfor affluent countries and the Afri-can region, and juxtaposes thiswith the fact of far higher rates ofhypovitaminosis A and xeroph-thalmia in the latter area. My col-league, Jesus Bulux and I pon-dered a series of observations thatled us, in 1993, to challenge theconventional bioconversion fac-tors (27). These included the factthat the range of hepatic vitaminA stores was lower in herbivoresthan in carnivores. Among hu-


mans, hepatic liver reserves werelower in vegans than in omni-vores. Hypovitaminosis A wasmost common in populations sub-sisting on primarily plant-baseddiets. In the most vulnerable popu-lation (preschoolers), getting ac-ceptance and consumption ofdark green leafy vegetables(DGLV) is problematic, and itwould be more difficult if programscalled upon youngsters to con-sume even more. In our review,we said: “Evidence from feedingstudies shows an almost univer-sally poorer intake of intactcarotenoids from plant sources asopposed to pure, chemicalsources. With notable exceptions,the bioconversion of plantcarotenoids to preformed vitaminA also seems to be inefficient.” Wewere overestimating vitamin Aavailability, underestimating risk,and overselling the promise of

plants to protect a population fromhypovitaminosis A and its conse-quences.

A team of investigators from theWageningen Agricultural Univer-sity placed it a bit more bluntly inthe title of a paper that appearedtwo years later in The Lancet:“Lack of improvement of vitaminA status with increased consump-tion of dark green leafy vegeta-bles” (28). In their conclusions,they assert: “There is little evi-dence to support the general as-sumption that dietary carotenoidscan improve vitamin A status. Ourfindings do not support the long-standing assumption that vitaminA deficiency can be combated byincreasing the intake of darkgreen leafy vegetables.”

Resistance to this notion of inac-curacy in the retinol equivalent

conversion factors came from aparticular source, namely theacademic community of the na-tion of India. For a people com-mitted to the Hindu faith, any no-tion of an obligatory necessity foranimals to become part of the dietwas anathema. The evidencebase for the conclusion of highbioconversion, however, werelargely from metabolic balancetechniques. Naturally, if therewere colonic destruction ofunabsorbed carotenoids, thiswould tend to augment the ap-parent absorption value fromsuch studies (29). This led tosometimes strident confronta-tions between those who soughtto reform the conversion factorsfor provitamin A from plant-baseddiets and those who sought toconserve their validity.

Prelude to retinol activityequivalents

If a population is in equilibrium,plant provitamin A can maintainstability of nutritional status (30),but it is not a robust approach forinterventions to remedy a popu-lation’s status. On the plant ma-trix side, research has shown thatmatrix factors in plant tissues canexplain the reason for lower avail-ability of plant provitamin A com-pounds for vitamin A in humans(31, 32), confirming the argu-ments of Solomons and Bulux(27) and de Pee et al. (28).

The prospects of efficient utilisa-tion from provitamin A, however,were not entirely bleak. On theβ-carotene-in-oil side, classicalmetabolic studies had examinedfunctional responses to restora-tion of vitamin A status usingβ-carotene dissolved in an oilymatrix (29). The reportedbioconversion efficiency had

Figure 2. Food supply of total vitamin A partitioned by the percentage avail-able from provitamin A carotenoids (cross-hatched segments, % indicated)and preformed vitamin A food sources (open segments), for the period 1979–81 (FAO/WHO Expert Consultation, 1988).


ranged from 2 to 25%. Recentstable-isotopic studies employingisotopic techniques have foundbioefficacies of from 5 (33) to 2.6µg (34) of β-carotene needed toproduce 1 µg of retinol.

At the conclusion of this round ofresearch, it became clear that notall provitamin A sources in naturewere created equal. It becameapparent to everyone in the fieldthat the 1967 REs were an over-valued currency in terms of mak-ing legitimate exchanges for vi-tamin A activity from plant-baseddiets. Thus, in January 2001, inthe United States and Canada weinitiated a new era of quantifyingdietary vitamin A with the desig-nation of the Retinol ActivityEquivalents (RAE) (35). Influ-enced by the research in the pre-vious decade, the U.S. Food andNutrition Board (FNB) basicallyhalved the official estimate forbioconversion efficiency of pro-vitamin A compounds in mostplant foods. The RAE is equiva-lent to 1 µg of all-trans-retinol, to12 µg of all-trans-β-carotene, andto 24 µg of other provitamin Acarotenes. On the other hand, theFNB spoke on the bioefficacy ofβ-carotene in oil. They stated:“The carotene:retinol equiva-lence ratio (µg:µg) of a low dose(less than 2 mg) of purified β-car-otene in oil is approximately2:1...” (35). With higher dosages,the efficiency decreases in amanner related to the totalamount of oil-based provitamin Asources presented.

The policy and programperspective

The late food scientist KennethSimpson commented almost twodecades ago: “Recent statisticsshow that carotene from vegeta-

bles contributes 68% of dietaryvitamin A on a world-wide basisand 82% in developing countries.In spite of the abundance of car-otene in the world, vitamin A de-ficiency is still a very seriousproblem.” (36). By applying theRAE retrospectively to these glo-bal estimates, it would be clearthat the contribution from pre-formed vitamin A, 32% and 18%,respectively, would remain con-stant in the recalculation whilethat from plants is cut in half.Hence, by this revision, the truevitamin A intakes would havebeen only 66% of what wethought it was for the world atlarge, and 59% of that estimatedfor developing countries.

Present and futureshock

At last we are armed with con-clusive and quantitative evi-dence, and almost a full consen-sus regarding the issues of theexpected bioefficiacy of oral pro-vitamin A compounds in their dis-tinct food formats. The recentpast guides us in the present toavoid excessive enthusiasm;overly enthusiastic expectationscan bring unintended conse-quences and damage the repu-tation of applied research and in-tervention programs as illus-trated in two case examples be-low.

Damaged reputations

Sometimes there is a cost in ex-cess mortality and public rela-tions to applying too high a dos-age of chemicals for nutritional“chemoprevention”. Both thecarotenoid and the vitamin Acommunities have suffereduproars regarding alleged dam-

age done to recipients of highdoses of the respective sub-stance in interventions. With re-spect to carotenoids, we havethe cancer prevention trialswith β-carotene provided daily orevery two days in multi-milligramdoses of β-carotene (37, 38) insubjects considered to be at riskof lung cancer by virtue of a his-tory of tobacco smoking or as-bestos exposure. A narrative in-terpretation of these studies hasbeen provided by Cooper (39).As we now know, the net effectwas a slightly higher mortalityrate among those in the β-car-otene intervention group. Anumber of explanations for thisparadoxical effect have been en-tertained (39, 40). The implica-tions of such unintended conse-quences is producing a “Badname for a perfectly good nutri-ent” (41). Since the context inthese trials was the isolated,chemical form in high doses andan unphysiological format, itshould have no implications fornatural provitamin A compoundsin their food forms (41).

More recently, in 2001 we havethe case of the Assam, India,and the vitamin A prophylaxispulse campaign with retinylpalmitate (see article by V.Reddyin this volume, ed.). This pro-vides another example of thepotential erosion of confidencein nutritional interventions anddamage to the reputation of vi-tamin A. In this instance, it wasthe safety of mass prophylaxiswith preformed vitamin A com-ing under scrutiny and frontal at-tack. The facts are in dispute(42). What is clear is that peri-odic high-dose supplementpulse campaign programs, inwhich all eligible preschoolers ina province are to be dosed on a


given day with imported cap-sules, have been conducted inIndia using a nationally preparedliquid elixir. It was generally ad-ministered as 2 ml volumes ona spoon, but acceptability issuesforced a change to small medi-cine cups of 5 ml capacity. Thedose was still to be 2 ml contain-ing 200,000 IU (60,000 RE).Whether or not some centresactually filled the cups produc-ing a 2.5-fold overdose or not,the claim was made in the after-math of the campaign that 14children had died as a direct re-sult of the vitamin A-dosing andmultiple others had suffered ad-verse side effects (42). The ex-istence of a scandal facts not-withstanding has produced offi-cial reticence regarding the pur-suit of periodic supplement dos-ing. A rapid retreat from the poli-cies and programs of vitamin Asupplementation without an ef-fective alternative would posepotential danger to the vitaminA nutriture of 80% of the world’spopulation.

Provitamin A answeringthe call in developingcountries

Both isolated β-carotene andhigh-dose retinyl palmitate areentering the 21st century withsomewhat tarnished reputationsfor safety, whereas provitamin Acarotenoids carry the scarlet let-ter of subperformance in thepublic health domain. Neverthe-less, newer knowledge of car-otenoids and more realistic ex-pectations can be parlayedinto the true realisation of theirpotential as a safe and effica-cious source of dietary vitaminA for the most needy of popula-tion groups.

Golden rice and othergilded grains

Dietary staples are so namedbecause they are the underpin-nings of cultural foodways; eve-ryone in the society would con-sume quantities of the dietarystaple. Hence, if one wants toassure that everyone in the so-ciety receives a given nutrient,it should be added to a staplefood. Rice is the staple grainthroughout the southern reachesof Asia, and may represent thestaple for one-half of humankind.In recent years, and primarilywith financing from theRockefeller Foundation, an effortin genetic biotechnology hasbeen applied to inserting into therice (Oryza sativa) the geneticmachinery that enables mari-golds and daffodils to makeβ-carotene. One or another ofthese approaches to makinggolden rice has been reportedfrom the Institute for Plant Sci-ence of the Swiss Federal Insti-tute of Technology in Zurich andthe Center for Applied Bio-sciences of the University ofFreiburg, Germany (43, 44). Thishas been much commentedupon as a paradigm of appliedgenetic biotechnology (45-47).

This approach has generated itsskeptics (48). Legitimate con-cerns exist that the plant will onlyexpress a fraction of the provi-tamin A needed. Persons wouldhave to consume more thanusual rations of rice to meet even50% of their vitamin A recom-mendation. Bioefficacy of provi-tamin A from a rice matrix is un-known. The efficiency ofbioconversion is likely to be low.The anthropological factor thatmay be critical is the acceptabil-ity of a rice that is “off-white” in

colour. Asian populations oftenput a high premium on the white-ness of their rice, and the yel-low colour may prove to be adetractor in terms of long-termacceptance.

The line of investigation is wor-thy of pursuit. What the ap-proach of golden rice – or anysimilar strategies with stapleproducts – requires is carefulstewardship by the professionalcommunities involved to avoidthe pitfalls that could lay in wait.This is an area for important con-tinuing research. Other staplesfrom white potatoes and othertubers (cassava, yams) to othergrains can be explored (49). Theinfluence of the lipid content ofthe diet is important in the as-sessment of effectiveness po-tential at the public health level.

One issue of safety would be toassure, if not so much for humanconsumption (about which thereis little question), but with regardto the environment isolation ofits genetic characteristics fromother rice crops where not de-sired. The other would be interms of efficacy. Learning thelesson from green and orangevegetables, we must not raiseexpectations for these geneti-cally altered crops beyond con-servative predictions, and notleave populations unprotected iftheir needs exceed the deliverycapacity of golden rice.

Carotene-pigmented oils

As reviewed above, when the lo-calisation of a provitamin A in afood is not in its tissues but inthe oil, a distinct set of circum-stances comes into play (33, 34)and the dietary vitamin A valuecan be considered full equivalent


to preformed vitamin A on aweight basis (35). Red palm oil(RPO) from the palm fruit (Elaeisguineensis) is a source of oil-emulsified α- and β-carotene inabundant concentrations (50,51). Crude RPO contains from500 to 700 ppm of carotenoids,of which 50% is β- and 37% is α-carotene. Some varieties have upto 4000 ppm (50). A commercialproduct from Malaysia contains45.5 mg of provitamin A ca-rotenoids per 100 g, in a ratio of28:18 in favour of α-carotene,which has conventionally beenquantified as providing 6000 REper 100 g.

In a comparative study of high-dose vitamin A supplementationin the Orissa Province of easternIndia, periodic dosing with RPOproduced the same degree of vi-tamin A status prophylaxis as didthe more traditional administra-tion of 200,000 IU of retinyl palmi-tate (52). This led me to commenton that finding: “It is now time toexplore β-carotene in foods in amatrix-free context, such as thepurified pigment and that in RPO,as the key to a safe and effectivevitamin A supplement, fortificant,and food-based solution allwrapped up in one” (53).

A much less well known, but po-tentially even richer source ofnatural provitamin A compoundsin oil is to be found in the previ-ously obscure “gac” fruit (Momor-dica cochinchinensis), native toVietnam (54). Its content of pro-vitamin A is greater than that ofthe palm fruit, and the potentialof feeding gac for improving vita-min A and carotene status inmalnourished Vietnamese chil-dren has been studied (54).

Bioefficacious provitaminA for the needs of infants

During the first year of life, issuesof vitamin A adequacy are para-mount. Two strategies – not mu-tually exclusive and both employ-ing retinyl palmitate supplements– are currently in vogue for pro-tection of the infant. One is thedirect supplementation of the in-fant with dosages at 7600 RE(25,000 IU) of vitamin A. The otheris the recommendation to providethe mother with one to two 200,000IU dosages within seven weeks ofdelivery. Should the stigma asso-ciated with high-dose preformedvitamin A extend to these two set-tings, the alternatives with provita-min A are uncertain.

With respect to the direct feed-ing of provitamin A in oils to in-fants, the lipase and bile salt se-cretion of infants requires devel-opment and maturation. Their di-gestive capacity is suited prima-rily to human milk and its fat con-tent and composition. It wouldtake about 125 ml of RPO to pro-vide 7500 RE (25,000 IU) of vita-min A activity, or 250 ml to pro-vide 15,000 RE (50,000 IU), us-ing the conventional RE assump-tions. How infants would tolerateand utilise this vehicle in thesedosages remains to be studied.

The International Research onInfant Supplementation (IRIS)group sponsored a four-nationsintervention trial with a compactedtablet as the vehicle (55). In a newmulticenter initiative (IRIS III) totest the potential of the fat-based,ready-to-use food in the form of aspread (56) to serve as the vehi-cle for food-based multi-micronu-trient intervention (57, 58), thedual source of vitamin A and E isbeing derived from RPO.

More is known about the indirectapproach of routing the vitaminA, as precursor provitamins, tothe infant via the mother and hermilk. This has been studied inHonduras (59, 60) and in Tanza-nia (61, 62). An improvement inthe vitamin A status of bothmother and offspring has beendemonstrated. Data from Lietz etal. (63) suggest that the ratio ofcirculating to breast milk β-carot-ene is roughly 10:1, independentof the absolute levels, and muchlower than the 5:1 ratio for lutein.

Bioefficacious provitaminA answering the call foraffluent populations?

There may be too much of a goodthing (vitamin A), i.e. when thatgood thing can also be a badthing. Hence, the utility of provi-tamin A as principal vitamin Asources for developed countriesalso has merit. The issues of tera-togenesis risk for fertile-agewomen (20) and life-long retinyl-ester intakes for bone health ofthe mature adult (21, 22) exem-plify the downside aspects of anincreasingly vitamin A-rich diet.So provitamin A as a fortificantmight be just what the epidemi-ologist ordered for the issue ofwilly-nilly fortification and self-supplementation in the U.S.

An oily supplement cock-tail for mature adults

Much is being learned aboutfunctions and actions of the fourfat-soluble vitamins and thecarotenoids, specifically for thehealth of the elderly. Argumentscan be made for at least assur-ing adequate nutriture, if not pro-viding supraphysiological sup-plies, of three of the fat-solublevitamins. For vitamin D, recom-


mendations for vitamin D five toten times that which is specifiedin the recent DRI-RDAs havebeen advanced (64, 65). For vi-tamin K, Booth et al. (66) havecited evidence for its role in bonehealth and mineralisation, impor-tant to counteract the oste-oporotic process of aging. Thebenefits of intakes of vitamin Ein preventing coronary heart dis-ease have been documented(67), and doses of the vitaminwell in excess of the RDA or thatcould ever be achieved from di-etary sources are immuno-regulatory in the elderly (68). Tothis constellation, we can add aseries of observations on thehealth promotional values oflycopene and the oxo-carotenes,lutein and zeaxanthin (69, 70).

Since the full efficiency of fat as-similation by the intestine re-quires a stimulation of lipase andbile salt secretion and intestinalcell lipoprotein packaging, theabsorption of fat-soluble nutri-ents, taken fasting on an emptystomach, is even more variableand limited. Promotion of the sup-plementation of mature adultswith fat-soluble nutrients mightentail their separation from wa-ter-soluble vitamins and miner-als, and their combination in a fat-based elixir or snack. Only vita-min A among the fat-soluble nu-trients must be used sparinglyand with caution in older individu-als (71). The resolution mightcome in using provitamin A caro-tenes as the vitamin A source,thus taking advantage of indi-vidual regulation mechanisms toadjust hepatic vitamin A reserves.In such an oil base, all of thementioned compounds shouldhave maximal bioefficacy.

The challenge forthe carotenoid re-search community

Extend the use of stableisotope research into de-veloping countries

The issues related to the true ef-ficiency of bioconversion of plantprovitamin A languished in con-fusion for decades in part be-cause of inappropriate designand interpretation of research(29). Policy-makers relied on cal-culations of “apparent absorp-tion” of carotenoids from meta-bolic balance studies without re-alising that colonic degradationproduced a systematic overesti-mation of the absorption values.The view that the poverty in de-veloping countries relegates thescientific effort to the most rudi-mentary technology has to bechallenged (71). In fact, JimOlson was an enthusiastic advo-cate of the application of stableisotopes to study vitamin A me-tabolism in the Third World (72,73). In recent years, his visionhas been exemplified (74), butcontinued investment in highertechnology, guided by the natureof the scientific question (not thatof the geographic setting), is re-quired to examine the efficacy ofprovitamin A-based solutions fordeveloping country hypovitami-nosis A.

Is the “low-responder”status a result of geneticpolymorphism?

Effective public health measuresrequire not that a population iscovered “on average”, but that asuitable level of protection isachieved by each and every vul-

nerable subject. A potential fly inthe ointment of substituting oil-based provitamin A for preformedvitamins in supplementation andfortification is the unresolved is-sue of “low responders”. Theseare a subsegment of the popula-tion that seems to represent asecond (lower) distribution for theability to effect bioconversion.Now that the enzymatic and mo-lecular basis of β-carotene cleav-age has been so well reviewed(13), mutations and polymor-phism emerge as viable explana-tions for heterogeneity in bio-conversion capacity. Wyss (13)states: “A considerable part of thepopulation is known as ‘low re-sponders’, these people haveunusual high β-carotene plasmalevels. They only cleave a smallamount of the absorbed β-carot-ene to form vitamin A. It wouldbe interesting to see if mutationsin the coding sequence of thedioxygenases or polymorphismsin the promoter region are re-sponsible for the difference seenin β-carotene cleavage amongthe population.” In terms of pub-lic policy, this has a practical con-text, as such individuals mighthave to be identified and selec-tively assigned to provitamin Atherapy in any shift over to gen-eral reliance on provitamin A.

Carotenoid actions indeveloping countries

James Allen Olson was a man forall seasons. His paradigm of“function” and “action” (3) sets thetone for the professional commu-nity. The challenge for the caro-tenoid research community is toinstitutionalise the dual vision of“function” and “action” when itcomes to the investigativeagenda for the next two decades.


For the 20% of the world’s popu-lation living in privileged condi-tions, abundant preformed vita-min A from animal products andfood additives in spreads andbreakfast cereals protects mostof the consumers (75). For the re-maining 80%, this is still a matterof sight and life, or blindness anddeath. The ironic novelty, how-ever, is that for this 80% of thepopulation, issues of chronic dis-ease prevention are beginning torise (76). The actions ofcarotenoids take on a new mean-ing while the functions of provi-tamin A remain eternal.

In a series of studies performedin Tanzania, morbidity and mor-tality in children were inverselyrelated to the calculated vitaminA intake of the habitual diet, al-though they were unaffected bylarge-dose supplements of pre-formed vitamin A (77, 78). Thus,either total food vitamin A activityis a marker for bioactive constitu-ents of the diet or the substancesaccounting for vitamin A activityare playing a role aside from theirprovitamin A role.

Gastric cancers have long beenthe primary malignancy for adultpopulations of low-income coun-tries. Abundant intakes of non-provitamin A carotenoids havebeen associated with lowerincidences of stomach malig-nancy (2, 69).

Finally, the health and antioxidantprotection of the ocular retina isimportant in preterm birth. Luteinand zeaxanthin are important tothis aspect of preterm nutrition(79). As survival of smaller andsmaller infants proceeds, this is-sue will loom larger in both de-veloped and developing coun-tries.

The professional communitymust continue to see its researchand food technology in terms ofthe dual mission of carotenoidsas dietary precursors of vitaminA (function) and carotenoids fortheir bioactive properties in pres-ervation of physiology and pre-vention of illness (actions). Aninspiration for this mission willforever be the life and works ofJames Allen Olson who clarifiedimportant biological and concep-tual points and cleared the chan-nels for decades of consolidationinvestigations to proceed.

References

1. Solomons NW. Obituary. InMemorium. James Allen Olson,1924–2000. Eur J Clin Nutr 2000, 55:65-67

2. Solomons NW. Vitamin A andcarotenoids. In: Bowman BA, RussellRM, eds. Present Knowledge inNutrition, 8th Edition. Washington:ILSI Press, 2001, pp 127-145

3. Olson JA. Carotenoids. In: Shils ME,Olson JA, Ross AC, Shike M, eds.Modern Nutrition in Health and Dis-ease. Philadelphia: WB Saunders,1998, pp 525-541

4. McCollum EV, Davis M. The neces-sity of certain lipins in the diet duringgrowth. J Biol Chem 1913, 15: 167-175

5. Osborne TR, Mendel LB. The influ-ence of butter-fat on growth. J BiolChem 1913,16: 423-437

6. Capper NS. The alleged contamina-tion of carotene by vitamin A.Biochem J 1930, 24: 453-455

7. Capper NW. The transformation ofcarotene into vitamin A as shown bya study of the absorption spectra ofrat liver oils. Biochem J 1930, 24:980-982

8. Moore T. The absence of the liver oilvitamin A from carotene. The conver-sion of carotene to vitamin A in vivo.Biochem J 1930, 24: 692-702

9. Olson JA, Hayaishi O. The enzymaticcleavage of beta-carotene into vita-min A by soluble enzymes of rat liver

and intestine. Proc Natl Acad Sci US A 1965, 54: 1364-1370

10. Goodman DS, Huang HS. Biosyn-thesis of vitamin A with rat intestinalenzymes. Science 1965, 149: 879-880

11. Nagao A, During A, Hoshino C, TeraoJ, Olson JA. Stoichiometric conver-sion of all-trans-ß-carotene to retinalby pig intestinal extract. ArchBiochem Biophys 1996, 328: 57-63

12. Barua AB, Olson JA. ß-Carotene isconverted primarily to retinoids in ratsin vivo. J Nutr 2000, 130: 1996-2001

13. Wyss A. Progress in ß-carotene andvitamin A research: cloning and char-acterisation of the ß,ß-carotene15,15' dioxygenase. SIGHT ANDLIFE Newsletter 2001; 4: 6-10

14. Wyss A, Wirtz G, Woggon W,Brugger R, Wyss M, Friedlein A,Bachmann HJ, Hunziker W. Cloningand expression of ß,ß-carotene15,15'-dioxygenase. BiochemBiophys Res Commun 2000, 271:334-336

15. Yan W, Jang GF, Haeseleer F, EsumiN, Chang J, Kerrigan M, Campo-chiaro M, Campochiaro P, Pal-czewiski K, Zack DJ. Cloning andcharacterisation of a human ß,ß-car-otene-15,15'-dioxygenase that ishighly expressed in the retinal pig-ment epithelium. Genomics 2001,72: 193-202

16. Krinsky N, Russell RM. Regardingthe conversion of ß-carotene to vita-min A (Letter). Nutr Rev 2001, 59:309

17. Kiefer C, Hessel S, Lampert JM, VogtK, Lederer MO, Breithaupt DE, vonLintig J. Identification and characteri-zation of a mammalian enzymecatalyzing the asymmetric oxidativecleavage of provitamin A. J BiolChem 2001, 276: 14110-14116

18. Milton K. Nutritional characteristicsof wild primate foods: Do the naturaldiets of our closest living relativeshave lessons for us? Nutrition 1999,15: 488-498

19. Cordain L. Cereal grains. Humanity’sdouble-edged sword. In: SimopoulosA (ed) Evolutionary aspects of nutri-tion and health: Diet, exercise, ge-netics and chronic disease. Basel: S.Karger, A.C., 1999, pp19-73

20. Rothman KJ, Moore LL, Singer MR,Nguyen US, Mannino S, Milunsky A.


Teratogenicity of high vitamin A in-take. New Engl J Med 1995, 333:1369-1373

21. Michaelsson K, Holmberg L, MallminH, Sorensen S, Wolk A, BergstromR, Ljunghall S. Diet and hip fracturerisk: a case-control study: StudyGroup of the Multiple Risk Survey onSwedish Women for Eating Assess-ment. Int J Epidemiol 1995, 24: 771-782

22. Melhus H, Michaelsson K, KindmarkA, Bergström R, Holmberg K,Mallmin H, Wolk A, Ljunghall S. Ex-cessive dietary intake of vitamin A isassociated with reduced bone min-eral density and increased risk for hipfracture. Ann Intern Med 1998, 12:770-778

23. Mathews-Roth MM. Carotenoids inerythropoietic porphyria and otherphotosensitivity diseases. Ann N YAcad Sci 1993, 691: 127-138

24. Food and Agriculture Organization/World Health Organization. Require-ments of vitamin A, thiamine, ribo-flavin and niacin. FAO Food andNutrition Series 8. Rome: FAO, 1967

25. Sommer A. New imperatives for anold vitamin (A). J Nutr 1989, 119: 96-100

26. McLaren DS, Frigg M. SIGHT ANDLIFE Manual on Vitamin A DeficiencyDisorders (VADD). Basel; Task ForceSIGHT AND LIFE, 1997

27. Solomons NW, Bulux J. Plantsources of vitamin A and human nu-triture. Nutr Rev 1993, 51: 199-204

28. De Pee S, West CE, Muhilal, KaryadiD, Hautvast JGAJ. Lack of improve-ment of vitamin A status with in-creased consumption of dark greenleafy vegetables. Lancet 1995, 346:75-81

29. Castenmiller JJM, West CE.Bioavailability and bioconversion ofcarotenoids. Annu Rev Nutr 1998,18: 19-38

30. Tang G, Gu X, Hu S, Xu Q, Qin J,Dolnikowski GG, Field CR, Go X,Russell RM, Yin S. Green and yel-low vegetables can maintain bodystores of vitamin A in Chinese chil-dren. Am J Clin Nutr 1999, 70: 1069-1076

31. Castenmiller JJM, West CE, LinssenJPH, van het Hof KH, Voragen AGJ.Food matrix of spinach is a limitingfactor in determining thebioavailability of ß-carotene but to a

lesser extent of lutein. J Nutr 1999,129: 349-355

32. van het Hof KH, Brouwer IA, WestCE, Haddeman E, Steegers-Theunissen RP, van Dusseldorp M,Westrate JA, Ekes TK, Hautvast JG.Bioavailability of lutein from vegeta-bles is 5 times higher than that ofbeta-carotene. Am J Clin Nutr 1999,70: 261-268

33. You Ch-S, Parker RS, Swanson JE.Bioavailability and vitamin A value ofcarotenes from red palm oil as-sessed by an extrinsic isotope refer-ence method. A paper presented inKuala Lumpur, Malaysia, 2001

34. van Lieshout M, West CE,Permaesih D, Wang Y, Xu X, vanBreemen RB, Creemers AFL,Verhoeven MA, Lugtenburg J.Bioefficacy of ß-carotene dissolvedin oil studied in children in Indone-sia. Am J Clin Nutr 2001, 73: 949-958

35. Food and Nutrition Board StandingCommittee of the Scientific Evalua-tion of Dietary Reference Intakes.Dietary reference intakes for vitaminA, vitamin K, arsenic, boron, chro-mium, copper, iodine, iron, manga-nese, molybdenum, nickel, silicon,vanadium and zinc. Washington DC;Institute of Medicine, National Acad-emy of Sciences, 2001

36. Simpson KL. Relative value ofcarotenoids as precursors of vitaminA. Proc Nutr Soc 1983, 42: 7-16

37. Alpha-Tocopherol, Beta-CaroteneCancer Prevention Study Group. Theeffect of vitamin E and beta-caroteneon the incidence of lung cancer andother cancers in male smokers. NEngl J Med 1994, 330: 1029-1035

38. Omenn GS, Goodman GE,Thornquist MD, Balmes J, CullenMR, Glass A, Keogh JP, MeyskensFL Jr, Valanis B, Williams JH Jr,Barnhart S, Cherniak MG, BrodkinCA, Hammer S. Effects of a combi-nation of beta-carotene and vitaminA on lung cancer and cardiovascu-lar disease. N Engl J Med 1996, 334:1150-1155

39. Cooper DA, Elridge AL, Peters JC.Dietary carotenoids and lung cancer:A review of recent research. Nutr Rev1999, 57: 133-145

40. Russell RM. The vitamin A spectrum:From deficiency to toxicity. Am J ClinNutr 2000, 71: 878-884

41. Solomons NW. Giving a bad nameto a perfectly good nutrient (Letter tothe Editor). Nutr Rev 1999, 57: 329-330.

42. Mudur G. Death triggers fresh con-troversy over vitamin A programmein India. BMJ 2001, 323: 1206

43. Ye X, al-Babili S, Kloti A, Zhang J,Lucca P, Beyer P, Potrykus I. Engi-neering the provitamin A (beta-car-otene) biosynthetic pathway into(carotenoid-free) rice endosperm.Plant J 1997, 11: 1071-1078

44. al-Babili, Ye X, Lucca P, Potrykus I,Beyer P. Biosynthesis of beta-carot-ene (provitamin A) in rice endospermachieved by genetic engineering. NatBiotechnol 2000, 18: 750-753

45. Anon. Golden rice. Nat Biotechnol2000, 18: 135

46. Guerinot ML. Perspectives: plant bi-ology. The green revolution strikesgold. Science 2000, 287: 241-243

47. Schiermeier Q. Designer rice to com-bat diet deficiencies makes its debut.Nature 2001, 409: 551

48. Nestle M. Genetically engineered“golden” rice unlikely to overcomevitamin A deficiency. J Am Diet Assoc2001, 101: 289-290

49. Potrykus I. Golden rice and beyond.Plant Physiol 2001, 125: 1157-1161

50. Narasinga Rao BS. Potential use ofred palm oil combating vitamin A de-ficiency in India. Food Nutr Bull 2000,21: 202-211

51. Ong ASH, Goh SH. Palm oil: Ahealthful and cost-effective dietarycomponent. Food Nutr Bull 2002, 23:11-22

52. Mohapatra S, Manorama R. The pro-tective effect of red palm oil in com-parison with massive vitamin A dosein combating vitamin A deficiency inOrissa, India. Asia Pac J Clin Nutr1997, 66: 246-250

53. Solomons NW. Plant sources of vi-tamin A and human nutrition. Redpalm oil does the trick. Nutr Rev1998, 56: 309-311

54. Vuong LT, Dueker SR, Murphy SP.Plasma ß-carotene and retinol con-centrations of children increase af-ter a 30-day supplementation withthe fruit Momordica cochinchinensis(gac). Am J Clin Nutr 2002, 75: 872-879


55. Gross R (ed). Micronutrient supple-mentation throughout the life cycle.New York: UNICEF, 2001

56. Briend A. Highly nutrient-densespreads: a new approach to deliver-ing multiple micronutrients to high-risk groups. Br J Nutr 2001, 85 (Suppl2): S175-S179

57. Briend A, Lacsala R, Prudhon C,Mounier B, Grellety Y, Golden MH.Ready to use therapeutic food fortreatment of marasmus (Letter). Lan-cet 1999, 353: 1767-1768

58. Briend A. Possible use of spreads asa FOODlet for improving the diets ofinfants and young children. FoodNutr Bull (in press)

59. Canfield LM, Kaminsky RG. Redpalm oil in the maternal diet improvesthe vitamin A status of lactating moth-ers and their infants. Food Nutr Bull2000, 21: 144-148

60. Canfield LM, Kaminsky RG, TarenDL, Shaw E, Sander JK. Red palmoil in the maternal diet increases pro-vitamin A carotenoids in breastmilkand serum of the mother-infant dyad.Eur J Nutr 2001, 40: 30-38

61. Lietz G, Henry CJK, Mulokozi G,Mugyabuso J, Ballart A, Ndossi G,Lorri W, Tomkins A. Use of red palmoil for the promotion of maternal vi-tamin A status. Food Nutr Bull 2000,21: 215-218

62. Lietz G, Henry CJK, Mulokozi G,Mugyabuso J, Ballart A, Ndossi G,Lorri W, Tomkins A. Comparison ofthe effects of supplemental red palmoil and sunflower oil on maternal vi-tamin A status. Am J Clin Nutr 2001,71: 501-509

63. Lietz G, Mulokozi M, Mugyabuso J,Ndossi G, Henry CJK, Tomkins Al.Does the breast cell control the up-take of lutein and β-carotene from

plasma? Abstract Program, Interna-tional Congress on Nutrition 17. AnnNutr Metab 2001, 45 (Suppl 1): 27

64. Dawson-Hughes B, Harris SS, KrallEA, Dallal GE. Effect of calcium andvitamin D supplementation on bonedensity in men and women 65 yearsof age or older. N Engl J Med 1997,337: 670-676

65. Vieth R, Chan P-CR, MacFarlaneGD. Efficacy and safety of vitamin D3intake exceeding the lowest ob-served adverse effect level. Am J ClinNutr 2001, 73: 288-294

66. Booth SL, Lichtenstein AH, O’Brien-Morse M, McKeown NM, Wood RJ,Saltzman E, Gundberg CM. Effectsof a hydrogenated form of vitamin Kon bone formation and resorption.Am J Clin Nutr 2001, 74: 783-790

67. Rimm EB, Stampfer MJ, Ascherio A,Giovannucci E, Colditz GA, WillettWC. Vitamin E consumption and therisk of coronary heart disease. N EnglJ Med 1993, 328: 1450-1456

68. Meydani SN, Han SN. Nutrient regu-lation of the immune response: Thecase of vitamin E. In: Bowman BA,Russell RM, eds. Present knowledgein nutrition, 8th Edition. Washington:ILSI Press, 2001, pp 449-462

69. Curran-Celentano J, Hammond BRJr, Ciulla TA, Cooper DA, Pratt LM,Danis RB. Relation between dietaryintake, serum concentrations, andretinal concentrations of lutein andzeaxanthin in adults in a Midwestpopulation. Am J Clin Nutr 2001, 74:796-802

70. Gerster H. The potential role oflycopene in human health. J Am CollNutr 1997, 16: 109-126

71. Scrimshaw NS. Appropriate tech-nologies for preventing malnutritionin developing countries. In:

Wahlqvist ML, Truswell AS, Smith R,Nestel PJ. eds. Nutrition in a Sus-tainable Environment. Proceedingsof the XV International Congress ofNutrition. London: Smith-Gordon,1994, pp 118-125

72. Olson JA. Isotope dilution tech-niques: a wave of the future in hu-man nutrition (editorial). Am J ClinNutr 1997, 66: 186-187

73. Olson JA. Vitamin A assessment bythe isotope-dilution technique: goodnews from Guatemala (editorial). AmJ Clin Nutr 1999, 69: 117-118

74. Solomons NW, Russell RM. “Appro-priate technology” for vitamin A fieldresearch (Editorial) Am J Clin Nutr2001, 73: 849-850

75. Berner LA, Clydesdale FM, DouglassJS. Fortification contributed greatlyto vitamin and mineral intakes in theUnited States, 1989–1991. J Nutr2001, 131: 2177-2183

76. Popkin BM. Nutrition transition andits health implications in low-incomecountries. Publ Health Nutr 1998, 1:1-21

77. Fawzi WW, Herrera MG, Willett WC,Nestel P, el Amin A, Lipsitz S,Mohamed KA. Dietary vitamin A in-take and the risk of mortality amongchildren. Am J Clin Nutr 1994, 59:401-408

78. Fawzi WW, Herrera MG, Willett WC,Nestel P, el Amin A, Mohamed KA.Dietary vitamin A intake and the inci-dence of diarrhea and respiratory in-fection among Sudanese children. JNutr 1995, 125: 1211-1221

79. Mayes CBD, Jewell VC, Northrup-Clewes CA, Tubman R, ThurnhamDI. Longitudinal measurements oflutein and zeaxanthin in the preterminfant. Abstract Program, Interna-tional Congress on Nutrition 17. AnnNutr Metab 2001, 45 (Suppl 1): 32


IntroductionDuring the period of more than aquarter of a century that I havebeen producing a regular digest,first for the Xerophthalmia ClubBulletin, and now SIGHT ANDLIFE Newsletter I have tried notonly to produce a faithful abstractof a paper but also to make per-sonal comments or criticismswhere these seemed to be ap-propriate.

It is interesting to note how thecontent of the digest has tendedto change over this period. In the1970s and 80s there was still astrong emphasis on xerophthal-mia and various aspects of theeffects of vitamin A deficiency onthe eyes. Since then increasinglyattention has been paid to ad-vances in knowledge of the ad-verse effects of vitamin A defi-ciency on other systems of thebody, its relationships to variousinfections and to its important rolein childhood mortality and mor-bidity, and more recently mater-nal mortality. From about thesame time the fundamental roleof retinoic acid with nuclearreceptors in gene transcriptionand other aspects at the molecu-lar biology level demanded atten-tion from anyone interested in vi-tamin A. It would clearly be inap-propriate for someone untutoredin this field to be so bold as to

make critical comments, butamong our readership there aresurely those who have this com-petence and such contributionswould be welcomed.

Some further remarks might bemade on the subject of com-ments and criticism. Most scien-tific and medical journals offertheir readership an opportunity tocontribute appropriate corre-spondence, as does this news-letter, and the topics covered inthis digest surely offer a greatopportunity to have your viewsbroadcast widely. To a close ob-server it should be evident thatin the VAD field insufficient atten-tion is being paid to some of thecriteria and standards that havebeen formally adopted by thescientific community working inthis field. Two examples, oneclinical and one biochemical,come readily to mind and willserve to illustrate the point thatis being made here.

The clinical example relates tothe use of the various eye signsindicative of xerophthalmia.These have been fully describedand their use commented uponin detail, originally in the two tech-nical reports of WHO (1976 and1982) but frequently more re-cently in other authoritative docu-ments. The criteria and standardsset, although to some extent ar-bitrary, are based on solid sci-ence and are universally agreedto have stood up to the test oftime. Nevertheless papers con-tinue to be approved by referees,

accepted by editors, and assimi-lated by interested scientists thatflagrantly flout in all kinds of waysthe approved methodology. Edi-tors and referees are to blame,but it is highly unlikely that theseguilty parties will be reading this!

The biochemical example relatesto a phenomenon that was firstobserved more than half a cen-tury ago. This is the fact that dur-ing what is known as the “acutephase response” (APR) retinoland some other plasma constitu-ents diminish, often dramatically.This renders it in these circum-stances unreliable as an indica-tor of vitamin A status. Manyyoung children in developingcountries who are being inves-tigated for suspected subclini-cal vitamin A deficiency will un-doubtedly be subject to variousinfections and infestations, mi-nor trauma and other ailmentsthat will activate in them tosome degree the APR. The criti-cism raised here applies, ofcourse, not only to serum reti-nol concentration per se butalso to any test in which it isused; i.e. relative dose response(RDR) and modified relativedose response (MRDR). Retinol-binding protein (RBP) which canserve as an appropriate surro-gate for retinol may not be soaffected (see paper by Sembaet al below). As far as I am awarethe effect of the APR on an indi-cator of nutritional status hasonly been investigated in thecase of retinol and albumin (forprotein status). What about otherconstituents of plasma like cho-lesterol, triglycerides and otherlipids, those employed to assessiron status, other vitamins andessential elements? Perhapssome helpful readers can shedsome light!

A Digest of Recent LiteratureDonald S. McLaren*

* Address for correspondence:Prof. Donald S. McLaren12 Offington Avenue, Worthing,West Sussex BN14 9 PE, UK


Blindness“Editorial: Global Partnershipto Preserve and Restore Vi-sion“ by Spivey BE. Am JOphthal 2002, 133: 822-824(One Beekman Place, New York,NY 10022, USA).This editorial comments for itsaudience of ophthalmologists onthe United Nations VISION 2020programme. Worldwide approxi-mately 45 million persons areblind and 135 million visually im-paired - so that they cannot readnewsprint with either eye evenwith the best possible spectacles.In two thirds the impairment isavoidable, with three quartersbeing due to cataract. It is esti-mated that the number of blindand visually impaired will doubleby 2020 unless concerted actionis taken.

Vitamin A deficiency is includedamong the causes of “prevent-able blindness” and consideredto have “largely a public healthsolution“. VISION 2020 focuseson three main areas: control ofmajor causes of blindness; hu-man resource development; andinfrastructure and appropriatetechnology development. VitaminA deficiency along with othercauses of childhood blindness isincluded as a major cause ofblindness to receive priority. Theother major causes are cataract,trachoma, onchocerciasis, andrefractive errors and low vision.(DSM, the editorial concludes -“ophthalmologists throughout theworld have a role of leadershipand responsibility in implementa-tion of VISION 2020“. This wastrue 30 years or so ago, but herethere is no recognition of thechanges that have occurredsince then. Xerophthalmia as acause of childhood blindness has

been greatly reduced over thisperiod. However, recognition hastaken place as to how subclini-cal vitamin A deficiency greatlyincreases the risk of young childand maternal mortality and mor-bidity. This outdated and out-moded approach to this seriousand widespread health problem,which incidentally is reflected inmajor medical textbooks (seeNewsletters 2/2001 p 10; 3/2001p 43) can only impede the imple-mentation of measures for itscontrol.)

“Non-trachomatous cornealopacities in the Gambia - aeti-ology and visual burden” byBowman RJC, Faal H, Dolin P,Johnson GJ. Eye 2002, 16: 27-32 (R Bowman, Ophthalmologyfellow, Great Ormond Street Hos-pital for Children, Great OrmondStreet, London WC1N 3JH, UK).Comparison of national blindnesssurveys conducted in the Gam-bia in 1986 and 1996 showed anincrease in blindness and visualimpairment from non-trachoma-tous opacity. This study aimed toinvestigate the causes and givesdetails of the total of 154 patients(39 bilateral and 115 unilateralopacities), out of 13046 peopleexamined. It is stated in the Meth-ods section that “aetiology of cor-neal opacity was ascribed on thebasis of history and examination“.No further details are given andno mention is made of the WHOTechnical Reports on Xerophthal-mia (see Introduction above) orof any other guidelines for itsdetection. Throughout the com-bined diagnosis of measles/vita-min A deficiency was used. “Ofthe aetiological categories thatwere identified, the most com-mon was corneal infection, fol-lowed by trauma, then measles/vitamin A deficiency, and then

harmful traditional practices in-cluding couching. Vitamin A defi-ciency and/or measles wasthought to be responsible for cor-neal opacity in an estimated 1200patients. Vitamin A-rich foodssuch as mango, papaya, and redpalm oil are readily availablethroughout Gambia and nutri-tional eduction together with ameasles immunisation programwhich already reaches 97% ofthe population should see thisproblem decreasing in the fu-ture“. (DSM - There are severaldisappointing features to this re-port. It comes from a reputableinstitution in the UK and it so hap-pens that I was responsible forteaching the subject of nutritionalblindness there for a number ofyears spanning the 1996 survey.On no occasion was I consultedabout the vitamin A aspects of thestudies. Xerophthalmia and mea-sles are not inevitably associatedand these two diseases havetheir own distinctive characteris-tics with regard to both eye ex-amination and history. It is evi-dent that none of these featureswas taken into account in com-ing to a diagnosis. Otheraetiologies may also accompanyxerophthalmia, especially tradi-tional practices and corneal infec-tion, but the possibility of theseconcurrences is not allowed for.Another feature that causes se-rious doubts as to the value ofthe study for making conclusionswith regard to past trends, thepresent situation, and recom-mending future action is the factthat the single most common cat-egory for both bilateral (56%) andmonocular (34%) cases was “un-known”).

“Environmental risk factors incongenital malformations ofthe eye” by Hornby SJ, Ward SJ,


Gilbert CE, Dandona L, Foster A,Jones RB. Ann Trop Paediatr2002, 22: 67-77 (Dept Epidemi-ology/Int Eye Hlth, Institute ofOphthalmology, 11-43 BathStreet, London EC1V 9EL, UK).Coloboma was selected as acommon congenital malformationof the eye. It consists of a defectin a tissue, in this case the iris,which extends inferiorly and re-sults from the failure of part of thefetal fissure to close. There is asuggestion that they are morecommon in India than elsewhere.Information on the possible roleof environmental factors, birth or-der, night blindness, drug use,maternal illness in pregnancy,rubella antibodies and exposureto agricultural chemicals was re-corded. Through hospital recordsand community-based rehabilita-tion programs in Andhra Pradeshchildren with colobomata wererecruited from schools for theblind. 83 mothers of children withcolobomata were interviewed.43% of parents were consan-guineious, 19% had a family his-tory and the frequency of colo-boma was highest in second-born children. 16% of mothershad a history of night blindnesswhile pregnant with the affectedchild, 8% took medication duringthe first trimester, 13% reportedexposure to agricultural chemi-cals. (It is very difficult to drawfirm conclusions from studies ofthis nature. The number of casesis small and by the nature of thesources of cases it is clear thatthey are not representative of anylarger grouping, posing difficultiesfor the making of general conclu-sions. There were no controlswith which to compare the datafrom the study group. It is notclear why schools for the blindshould house children with colo-bomata. Unless they are accom-

panied by other more seriousocular defects colobomata do notcause blindness and may onlyslightly impair vision in one eye).

Community studies“Activitating the communityfor nutritional improvement”by Devadas RJ. Food Nutr Bull2002, 23: 119-132 (The authordied on March 17, 2002. For sev-eral decades she was one of theleading figures in the field of foodand nutrition in India. This issuecarries a fitting tribute. This arti-cle summarises the communityaspects of her valuable contribu-tions).Among the many studies carriedout and described here is a sec-tion dealing with vitamin A defi-ciency. 500 households and thelocal market were surveyed anda seasonal calendar for locallyavailable vitamin A-rich foodswas developed. This calendar,containing information on vitaminA value and cost, is used in edu-cational programs. Another studyshowed that the introduction ofcrude red palm oil markedly re-duced clinical signs of vitamin Adeficiency in young children. Theencouragement of developmentof backyard gardens had a simi-lar beneficial effect.

“Control of vitamin A defi-ciency in Vietnam: achieve-ments and future orientation”by Khan NC, Khoi HH, Giay T,Nhan NT, Nhan NT, Dung NC,Thang HV, Dien DN, Luy HT.Food Nutr Bull, 23: 133-42 (Na-tional Institute of Nutrition, Hanoi,Vietnam).This paper reports on the activi-ties in Vietnam over the periodfrom 1985 - 1998 to control a se-rious public health problem ofVAD. Nationwide there was insti-

tuted universal vitamin A capsulesupplementation according toWHO criteria, dietary improve-ment through promotion of foodproduction and consumption atthe family level, and developmentof community nutrition educationactivities. Success is claimed forthese measures but the data pro-vided do not warrant this conclu-sion. (DSM: 1) in the 1985-88survey neither XN nor X1B ex-ceeded the WHO criteria for apublic health problem. AlthoughX2/3 and XS did, these criteriafor complex reasons cannot ontheir own be relied upon for acommunity diagnosis. 2) Severaltables of hospital data on“xerophthalmia”, without any defi-nition with regard to differentstages, are presented as evi-dence of improvement. Suchdata are notoriously unrepre-sentative of the community atlarge. 3) Recent data (1995 -8)on serum retinol of children < 5years show more than 10% havelow levels (<0.70 µmol/l). 4) Simi-lar data for breast milk retinolshow low levels (<1.05 µmol/l) in40% (1995), 49% (1997), and59% (1998) - suggesting the con-tinuing presence of a VAD prob-lem and possibly deteriorating.5) Finally, as so often happens,no account is taken of the likelyinfluence, for good or bad, ofmany other factors, all uncon-trolled and many unknown.)

“Vitamin A status of pre-schoolchildren in Ibadan, Nigeria.Risk factors and comparisonof methods of diagnosis” byAkinyinka OO, Usen SO, AkanniA, Falade AG, Osinusi K,Ajaiyeoba IA, Akang EE. West AfrJ Med 2001, 20: 243-8 (Depart-ment of Paediatrics, College ofMedicine, University CollegeHospital, Ibadan, Nigeria).


A cross-sectional study of 128healthy and 230 malnourished(PEM) preschool children in-cluded serum retinol and CIC-T.Low vitamin A status (serum reti-nol <10µg/dl) and abnormal CIC-T were similar (7.3%) and (6.2%)in all children. VAD was presentin 6.3% of healthy and 7.8% ofmalnourished children. Childrenaged 3 years accounted for 70%of VAD cases. Measles, persist-ent diarrhoea, and wasting pre-disposed to VAD. CIC-T was pre-dictive of serum retinol of 10µg/dlwith sensitivity of 83.3% andspecificity of 73.3%, suggestingits value as a screening tool.

“Assessment of vitamin A sta-tus of preschool children inIndonesia using plasma reti-nol-binding protein” by SembaRD, Yuniar Y, Gamble MV, Nata-disastra G, Muhilal A. J TropPediatr 2002, 48: 84-7 (OcularImmunology Service, Departmentof Ophthalmology, Johns HopkinsUniversity School of Medicine,Baltimore MD 21205, USA).This study tested the value of RBPas a surrogate for serum retinoland whether it was influenced byfactors such as inflammation andprotein status (see Introductionabove). In 236 preschool childrenthe Spearman correlation coeffi-cient between plasma RBP andretinol concentrations was 0.55(p<0.0001). By linear regression0.70 µmol/l retinol was equivalentto 0.69 µmol/l RBP. With thesecut-offs for defining VAD RBP hada sensitivity and specificity of 75%and 63.2% respectively. Thecorrelation between RBP and reti-nol was not affected by inflamma-tion markers or serum albumin(marker for PEM), suggesting RBPis a suitable retinol surrogate.

“Vitamin A for preventing sec-ondary infections in childrenwith measles - a systematicreview” by D-Souza RM, D-Souza R. J Trop Ped 2002, 48:72-77 (National Centre Epidemi-ology/Population Health, Austral-ian National University, Can-berra, ACT 0200, Australia).This was a meta-analysis includ-ing 492 children, aged 6 monthsto 13 years treated with vitaminA and 536 given placebo, in 6 tri-als. There was no significant re-duction in the incidence of pneu-monia or diarrhoea, but a 47% re-duction in croup in those given vi-tamin A. A significant decrease induration of diarrhoea, pneumonia,hospital stay and fever was re-ported. Vitamin A should be givento all hospitalised cases of mea-sles.

“Randomized double-blindtrial of the effect of vitamin Asupplementation of Indone-sian pregnant women on mor-bidity and growth of their in-fants during the first year oflife” by Schmidt MK, Musli-matum S, Schultink W, West CE,Hautvast JGAJ. Eur J Clin Nutr2002, 56: 338-46 (Division ofHuman Nutrition, WageningenUniversity PO Box 8129, 6700EV Wageningen, Netherlands).Supplementation comprised120 mg iron and 500 µg folic acidwith or without 4800 RE vitaminA. Additional vitamin A had nobeneficial effect on infant growthover 1 year, immunisation cov-erage, feeding mode or mor-bidity. Infants with serum reti-nol >0.70 µmol/l had greatergrowth than those with lower lev-els. Serum retinol was not asso-ciated with morbidity.

“Effect of vitamin A adminis-tered at expanded program onimmunization contacts on an-tibody response to oral poliovaccine” by Bahl R, Bhandari N,Kant S, Molbak K, Ostergaard E,Bhan MK. Eur J Clin Nutr 2002,56: 321-5 (Department ofPediatrics, All India Institute ofMedical Sciences, Center for Di-arrheal Disease/Nutrition Re-search, Ansari Nagar, New Delhi110029, India).Vitamin A given to mothers in thepostpartum period and their in-fants with oral polio vaccine didnot interfere with the antibodyresponse to any of the threepolioviruses given and enhancedthe response to polivirus type 1.

“Effect of vitamin A supple-mentation on measles-specificantibody levels in Guinea-Bissau” by Benn CS, Balde A,George E, Kidd M, Whittle H,Lisse IM, Aaby P. Lancet 2002,359: 1313-4 (Danish Epidemiol-ogy Science Centre, Statens Se-rum Institute, Copenhagen, Den-mark).This group previously reportedvitamin A with measles immuni-sation at 9 months increasedmeasles-specific antibody con-centrations at age 18 mo.Reexamination at 6-8 yearsshowed fewer vitamin A supple-mented children had non-protec-tive antibody concentrations(p=0.0095) and among those withprotective antibody levels theytended to have higher geometricmean antibody titres (p= 0.09).

“Vitamin A supplementationand human immunodeficiencyvirus type 1 shedding inwomen: results of a random-ized clinical trial” by Baeten J,McClelland RS, Overbaugh J etal. J Infect Dis 2002, 185: 1187-


91 (University of Washington,325 Ninth Avenue, Box 359909,Seattle, WA 98104-2499, USA).Using a variety of tests no evi-dence was found for any effectof supplementation on infectivityof women infected with HIV-1.

“Vitamin A deficiency andgenital viral burden in womeninfected with HIV-1” by FrenchAL, Cohen MH, Gange SJ et al.Lancet 2002, 359: 1210-2 (Divi-sion of Infectious Diseases,Durand 115, Cook County Hos-pital, Chicago IL 60612, USA).In 301 women infected with HIVvirus no association was foundbetween retinol status and geni-tal HIV-1 load. This lends supportto other studies that report no as-sociation between retinol defi-ciency and perinatal HIV-1 trans-mission.

Multi-micronutrients

“Effectiveness and efficacy ofzinc for the treatment of acutediarrhoea in young children”by Arne ST, Krisna CR, Rajiv Bet al. Pediatrics 2002, 109: 898-903 (Center for InternationalHealth, University of Bergen,Bergen, Norway).1792 cases of acute diarrhoea inNepalese children were ran-domized to 4 study groups. Threegroups were blinded and childrensupplemented daily with placebo,zinc, zinc plus vitamin A. A fourthgroup was open and the care-taker gave the children zinc daily.It was concluded “3 RDAs of zincdaily substantially reduced theduration of diarrhoea. The effectof zinc was not dependent on orenhanced by concomitant vita-min A administration“.

“A double-blind, placebo-con-trolled study of vitamin A andzinc supplementation in per-sons with tuberculosis in Indo-nesia: effects on clinical re-sponse and nutritional stutus”by Karyadi E, West CE, SchultinkW et al. Am J Clin Nutr 2002, 75:720-7 (Division of Human Nutri-tion, Wageningen University, POBox 8129, 6700 EV Wageningen,Netherlands).In this case-control study vitaminA and zinc supplementation im-proves the effect of tuberculosistreatment after 2 months, andresults in earlier sputum smearconversion.

“Effect of routine zinc supple-mentation on pneumonia inchildren aged 6 months to 3years : Randomised controlledtrial in an urban slum” byBhandari N, Bahl R, Taneja S etal. Brit med J 2002, 324: 1358-61 (Dr MK Bhan, Department ofPaediatrics, AIIMS, Ansari Nagar,New Delhi 110029, India).2482 New Delhi slum childrenaged 6 to 30 months participated.Both groups received vitamin A,one received additional zinc. Inthis latter group the incidence ofpneumonia was substantiallylower.

Basic studies“Vitamin A supplementationameliorates butyric acid-in-duced intestinal mucosal in-jury in newborn rats” by NafdaySM, Green RS, Chauvin SN etal. J Perinat Med 2002, 30: 121-7 (Dr J Lin, Lack/Lucy Clark De-partment of Pediatrics, Divisionof newborn Medicie Box 1508,One Gustave L Levy Place, NewYork, NY 10029-6574, USA).The lesion induced simulatedneonatal necrotizing enterocoli-

tis. Supplementation improveddaily weight gain, and at sacrificecolon wet weight was heavier andhistology injury scores for ileumand proximal colon were better.

“Mechanism of protection in-duced by vitamin A infalciparum malaria” bySerghides L, Kain KC. Lancet2002; 359: 1404-6 (Tropical Dis-ease Unit, Division of InfectiousDiseases, Department of medi-cine, Toronto General Hospital,Ontario M5G 2C4, Canada).Supplementation with vitamin Apotentiates host resistance tomalaria, but the underlyingmechanism is unknown. The ef-fects of 9-cis-retinoic acid weretested on various aspects of theimmune process. These includedCD36 expression (a mediator ofthe phagocytosis of non-op-sinised parasitised erythrocytes),non-opsonic phagocytic clear-ance of parasitised erythrocytes,and TNFalpha (tissue necrosisfactor) production in humanmonocytes and macrophages.This study found reduced secre-tion of TNFalpha, upregulatedCD36 expression, and increasedphagocytosis of Plasmodiumfalciparum-parasitised erythro-cytes. The resulting enhancedparasite clearance and inhibitionof excessive proinflammatory re-sponses might partly explain thebeneficial effects of vitamin Asupplementation in malaria.

“Oxidative stress-independentdepletion of epidermal vitaminA by UVA” by Sorg O, Tran C,Carraux P, Didierjean L, FalsonF, Saurat J-H. J Invest Dermatol2002, 118: 513-8 (Department ofDermatology, University Hospital,Geneva, Switzerland).In hairless mice epidermal vita-min A is markedly decreased fol-


lowing a single exposure to UVB.In this study the effect of UVAexposure was similarly studied.UVA exposure induced lipidperoxidation as well as reducingvitamin A content, not byoxidative stress but probably bya photochemical reaction inwhich UV radiations at about 325nm are involved.

“Prevention of vitamin A tera-togenesis by phytol orphytanic acid results from re-duced metabolism of retinol tothe teratogenic metabolite, all-trans retinoic acid” by ArnholdT, Elmazar MMA, Nau H. ToxicolSci 2002, 66: 274-282 (ZentrumLebensmittelwissenschaften,Tierärztliche HochschuleHannover, Germany).Phytol and phytanic acid, ineffec-tive when administered alone, didnot potentiate the teratogenicityinduced by retinol or retinoic acid(RA). In fact they effectivelyblocked the teratogenic effects ofretinol by markedly reducing themetabolic production of RA. It issuggested that phytol andphytanic acid may be useful forthe prevention of vitamin Ateratogenicity.

“Expression of cellular retinol-and retinoic acid-binding pro-teins in normal and pathologichuman parathyroid glands” byMelhus H, Li Q, Nordlinder H,Farnebo LO, Grimelius L. EndocrPathol 2001, 112: 423-7 (Depart-ment of Medical Sciences,Uppsala University Hospital, S751 85 Uppsla, Sweden).The group previously reportedhuman parathyroid gland as atarget organ for vitamin A.Stellate cells were identified inthis study. CRABP 1 (cellularretinoic acid binding protein) waspresent in cytoplasm, cell mem-

branes, and nuclear membranesof normal glands, but only excep-tionally in nuclear membranes ofabnormal glands. Since RA inhib-its the secretion of parathyroidhormone and CRABP 1 isthought to play a key role in regu-lating the amount of RA availableto interact with specific nuclearreceptors, these results suggestimpaired transport of RA to cellnuclei as a possible cause of hy-perparathyroidism.

“Expression studies of keyadipogenic transcriptional fac-tors reveal that the anti-adipo-genic properties of retinol inprimary culture humanpreadipocytes are due to reti-nol per se” by Machinal-QuelinF, Dieudonne MN, Leneveu MC,Pecquery R, Castelli D, Oddos T,Guidicelli Y. Int J Cosmet Sci2001, 23: 299-308 (Service deBiochimie, Centre HospitalierIntercommunal, 78303 PoissyCedex, France).This study was designed to in-vestigate the mechanisms of theanti-adipogenic effect of retinolpreviously reported by this group.It was shown that retinol per seinhibits the adipo-conversion ofhuman preadipocytes and it issuggested that at least in partinhibition of C/EBP (alpha) tran-scriptional activity is involved.

“Elaboration and characteriza-tion of whey protein beads byan emulsification/cold gelationprocess: application for theprotection of retinol” byBeaulieu L, Savoie L, Paquin P,Subirade M. Biomacromolecules2002, 3:239-248 (STELA DairyResearch Centre, Faculty of Ag-ricultural Science and Ali-mentation, University of Laval,Quebec, G1K 7P4, Canada).Full technical details are given of

a new method of producing wheyprotein beads to protect sensitivemolecules like retinol.

“Vitamin A enhances in vitroTh2 development via retinoidX receptor pathway” byStephensen CB, Rasooly R,Jiang X, Ceddia MA, Weaver CT,Chandraratna RAS, Bucy RP. JImmunol 2002, 168: 4495-503(US Department of AgricultureWestern Human Nutritional Re-search Center and Nutrition De-partment, University of California,Davis, CA 95616, USA).It has been shown that vitamin Adeficiency diminishes Th2-medi-ated Ab responses and that treat-ment with RA or high level dietaryvitamin A enhances such re-sponses. This study showed thatstimulation of the RXR pathwayenhances Th2 development, per-haps by affecting the relative ex-pression of pertinent transcriptionfactors, cytokines, and cytokinereceptors.

“Vitamin A deficiency pro-motes bronchial hyper-reactivity in rats by alteringmuscarinic M(2) receptor func-tion” by McGowan SE, Smith J,Holmes AJ, Smith LA, BusingaTR, Madsen MT, Kopp UC, KlineJN. Am J Physiol Lung Cell MolPhysiol 2002, 282 : 1031-9 (De-partment of Veterans Affairs Re-search Service, University ofIowa College of Medicine, IowaCity, Iowa 52242, USA).This study was undertaken in anattempt to contribute to the un-derstanding of lung infections indeveloping countries. VAD led tobronchial constriction developingat lower concentrations of inhaledmethacholine. The function andabundance of muscarinic re-ceptors were reduced in VADrats. Retinol and its congeners


may be required to regulate bron-chial responsiveness in additionto maintaining a normal bronchialepithelium.

“Midkine is involved in kidneydevelopment and its regulationby retinoids” by Vilar J, LalouC, Duong Van Huyen JP, CharrinS, Hardouin S, Raulais D, MerletBC, Lelievre PM. J Am SocNephrol 2002, 13: 668-76 (Unitéde Recherches, INSERM U356,IFR 58, Université Paris 6,France).It has been shown that retinoidsmodulate nephrogenesis in adose-dependent manner in vitroand in vivo. Midkine (MK) is aretinoic acid-responsive gene fora heparin-binding growth factor.This study showed that MK is im-plicated in the regulation of kid-ney development by retinoids. Itis also suggested that MK playsan important role in the molecularcascade of the epithelial conver-sion of the metanephric blastema.

“Vitamin A modulates the ef-fects of thyroid hormone onUDP-glucoronosyltransferase(UGT) expression and activityin rat liver” by Haberkorn V,Heydel JM, Mounie J, Artur Y,Goudonnet H. Mol Cell Endo-crinol 2002, 190: 167-75 (U deBiochim-Pharmacol-Toxicol, EA/MENRT 2980 UFR Pharmacie,Université de Bourgogne, 7 Bd.Jeanne d’Arc, 21079 Dijon,France).The study showed that thyroidhormones and vitamin A are co-regulators of the UGT1 familyexpression, without affecting theUGT2 family. By modifying activ-ity and expression of the bilirubinisoform, a member of the UGT1family, thyroid hormone reducedthe glucuronidation of T4 and rT3.

“Vitamin A deficiency duringrat pregnancy alters placentaltumour necrosis factor (TNF)-(alpha) signalling andapoptosis” by Antipatis C,Ashworth CJ, Riley SC, HannahL, Hoggard N, Lea RG. Am JReprod Immunol 2002, 47: 151-8 (Ovine Pregnancy group, Divi-sion of Integrative/developmen-tal Biology, Rowett Research In-stitute, Greenburn Road,Bucksburn, Aberdeen AB21 9SB,UK).Vitamin A is important for immunefunction and deficiency is asso-ciated with adverse pregnancyoutcome. This study showed thatmaternal vitamin A deficiency isassociated with abnormal pla-cental apoptosis induced by neu-trophil derived TNF-(alpha) act-ing through the TNFR1 (p55)and/or a change in the bcl-2/baxratio in the trophoblast giant cells.These changes may underlie theeffects of vitamin A deficiency onfetal development.

Carotenoids“Carotenoid composition andvitamin A value of an Argentin-ian squash (Cucurbita mo-schata)” by Gonzalez E,Montenegro MA, Nazareno MA,Lopez-de-Mishima BA. ArchLatinoam Nutr 2001, 51: 395-9(Instituto de Cienias Quimicas,Facultad del Estero, Santiago delEstero, Republica Argentina).A detailed profile, not includingcis-isomers, of carotenoids byHPLC is given. The total vitaminA value is 432 µg RE/100g freshsample. (In the Sight and LifeManual page 11 another sampleof cucurbita contained 862 µgand dark green leafy vegetableswere also higher at 685 µg).

“Variability in conversion of βββββ-carotene to vitamin A in menas measured by using a dou-ble-tracer study design” byHickenbottom SJ, Follett JR, LinY, Dueker SR, Burri BJ,Neidlinger TR, Clifford AJ. Am JClin Nutr 2002, 75: 900-7 (De-partment of Nutrition, Universityof California, Davis, CA 95616,USA).The vitamin A activity of β-carot-ene is variable and surprisinglylow in women. The activity in menis still uncertain. This study useda double-tracer test-retestmethod in 11 healthy men. Only6 men had sufficient plasma con-centrations of D6 β-carotene andD3 retinol that could be meas-ured. The authors conclude thatthe activity, even when measuredunder controlled conditions, wassurprisingly low and variable.

“Plasma βββββ-carotene and retinolconcentrations of children in-crease after a 30-d supplemen-tation with the fruit Momordicacochinchinensis (gac)” byVuong Le T, Dueker SR, MurphySP. Am J Clin Nutr 2002, 75: 872-9 (Department of Nutrition, Uni-versity of California, Davis, CA95616, USA).This fruit is commonly used inVietnam with rice (xoi gac). Oflocal sources it has the highestknown vitamin A activity. 185 pre-school children with low haemo-globin were assigned to one ofthree groups - 1) fruit group re-ceived xoi gac that contained 3.5mg β-carotene per serving; 2)powder group received ricemixed with 5.0 mg syntheticβ-carotene powder; 3) controlgroup received rice without forti-fication. Groups 1 and 2 had sig-nificantly higher plasma β-carot-ene than the control group. Theplasma retinol was significantly


higher in group 1 than in groups2 or 3. In children with Hb < 110g/l group 1 had significantlyhigher increase in Hb than con-trol but not different from group2. Vitamin A and Hb status wereboth improved by gac supple-mentation of children’s diet.

“Influence of dietary fat on βββββ-carotene absorption andbioconversion into vitamin A”by Ribaya-Mercado JD. Nutr Rev2002, 60: 104-10 (USDA HumanNutrition Research Center forAging, Tufts University 711

Washington Street, Boston MA02111, USA).Dietary fat is required for the ab-sorption of β-carotene and theminimum has been reported to beas little as 3-5 g. However, nec-essary long-term studies havenot yet been undertaken. Bodystores need to be measured andthis can now be done by the useof stable isotope dilution meth-ods. Animal studies have shownthat higher liver vitamin A concen-trations have resulted whenhigher dietary fat accompaniedthe carotenoid. Other factors also

need to be investigated, such astype of fat ingested, physico-chemical properties of carotenoidsource, amount of carotene in-gested, whether fat and carotenesources are provided in the samemeal, the presence of helminthinfestations, age and vitamin Astatus. (Clearly much work is re-quired before these importantquestions can be answered).

SIGHT AND LIFE homepage on CD, update June 2002

Slides andpresentations

SIGHT AND LIFE has prepareddifferent slide sets and presen-tations. The standard slide set (S-slides, 57 slides) was preparedalong with the manual while theP-slides (54 slides) were col-lected to complete presentationsas given by the three examplesP1, P2 and P3. In order to allowmost flexible use for the compo-sition of presentations slides aregiven in the formats JPG, PDFand PowerPoint (PPT). Also thewhole sets as well as the indi-vidual slides are given.

Besides making available allslides as PPT we also haveadapted the format for presenta-tion digitaly. However, we stillhave hardcopies of both series(P-slides only a limited number)available.


The SIGHT AND LIFE NEWSLETTER 3/2002 is a publicationof the Task Force SIGHT AND LIFE, PO Box 2116, 4002 Basel,Switzerland. Editor: Martin Frigg; Assistance: Franziska Horat,Anne-Catherine Frey, Claudia Rickli, Sandra Kölliker.Tel.: +41 61 688 74 94, Fax: +41 61 688 19 10, E-mail:[email protected]; www.sightandlife.org; ISBN 3-906412-14-8

The Task Force SIGHT AND LIFEis a humanitarian initiative byF. Hoffmann-La Roche Ltd to helpcombat nutritional blindness andall forms of vitamin A deficiency. Alow intake of vitamin A, termedsubclinical deficiency, is impairingthe health of children in numerousdeveloping countries. Increasedhealth risk with susceptibility to in-fections and increased child mor-tality are the consequences.

Opinions, compilations andfigures contained in the signedarticles do not necessarily rep-resent the point of view of SIGHTAND LIFE and are solely the re-sponsibility of the authors.

SIGHT AND LIFE has supportednumerous locally and internationallyactive organisations. Blindness pre-vention, research and applicationprojects in many countries in Africa,Asia and Latin America have beensponsored. Vitamin A, mostly in theform of capsules, grants, informa-tion and educational materials, suchas books, posters, reprints etc, arecontributed. Furthermore, SIGHTAND LIFE gives technical assist-

ance, if necessary, and promotionof training and education aims toincrease local knowledge and ex-pertise in order to work towards sus-tainable improvement of nutrition.

SIGHT AND LIFE publishes edu-cational materials as well as aNewsletter to disseminate knowl-edge on vitamin A and nutritionand to give relevant information onprograms and scientific news.

sight and life newsletter - a2zproject.orga2zorg/pdf/30 2002 sl.pdf · sight and life page 108...

Documents