Download - Cheerz ATH NewScience
7/28/2019 Cheerz ATH NewScience
http://slidepdf.com/reader/full/cheerz-ath-newscience 1/4
7/28/2019 Cheerz ATH NewScience
http://slidepdf.com/reader/full/cheerz-ath-newscience 2/4
l and smoke are major sources ofthepotent toxin acetaldehyde
IT'SHARD to look fetching with a
hangover. Curtains closed, you lie in
bed with a parched mouth, pounding
head and queasy stomach. On your way to the
kitchen for a glass of water you catch sight of
yoursel f in a mirror. Not a pretty sight. And if
you could witness the state of your insides
you'd be even more horrified .
Youare probably blaming your haggard
state on dehydration. or impurities in
whatever it was you drank last night, but
you're only partly right. Another big reasonfor your hangover is a simp le molecule called
acetaldehyde, produced by your liver as it
breaks down ethanol. Youcan take comfort
from the fact that once the acetaldehyde has
cleared from your system you will feel a lot
better, but your internal organs are n't so
lucky. They will be feeling the effects of
acetaldehyde for much longer.
Fora long time, acetaldehyde was
thought to be a harmless intermediate in the
breakdown of ethanol and was pretty much
ignored.Then its sinisteredge began to
emerge. It started in the 1980s when alcohol
researcher Victor Preedy of King's CollegeLondon found that acetaldehyde is a powerful
muscle poison. roughly 30 times more toxic
than ethanol itself.
It has since become clear that acetaldehyde
is the real demon in the demon drink. For
30 years researchers have known that excessive
alcohol intake causes serious long-term
damage to virtually every internal organ:
brain, kidneys, gonads, skeletal muscle, liver,
heart, uterus and digestive system. The
assumption was that ethanol itself was to
blame, but the mechanism was unclear.
Now,as we find out more about how drink
wreaks long-term havoc, the spotlight is
increasingly mo ving away from ethanol and
towards aceta ldehyde.
It's not just our boozing habits that are to
blame.Tobacco smoke. exhaust fumes and
foods all contribute to your acetaldehyde load.
The bacteria living in your mouth and guts
churn it ou t in bucket loads. The onslaught on
your body comes from within and without.
Measuring overall acetaldehyde exposure
is tricky as the molecule is quickly broken
down in the body, but researchers now believe
that acetaldehydeis at least partly responsible
for the rising incidence of cancer and liver
disease as well as, possibly,Alzheimer's.
Forsuch an innocuous-looking molecule,
acetaldehyde issurprisingly toxic. "With the
kind oflevels we take in, most of us should be
dead," says Richard Deitrich, a pioneer in
acetaldehyde research at the University of
Colorado Alcohol Research Center in Aurora.
Fortunately, the body has a battery of
detoxifying enzymes that specialise in
breaking the stuffdown .
10 february 20071 NewScientist 131
7/28/2019 Cheerz ATH NewScience
http://slidepdf.com/reader/full/cheerz-ath-newscience 3/4
Almost every tissue in th e body is
quipped with the enz ymes known as
ldehyde dehydrogen ases (ALDHs), which
er t ace ta ldehyde to harmless acetic acid.
here are 19different ALDHsin humans bu t
e in partic ular, ALDH2, does most of th e
especially in the liver .
As soo n as you sta rt dr ink ing alcohol,
ur liver revs into ac tio n. First, it converts the
thanol into acetaldehyde using another
me, alcohol dehydrogen ase.
etaldehyde is then broken down by ALDH2n d th e resultin g acetica cid is burned as fue l
the muscles. The live r does a fantastic job:
ormally it elim ina tes over 99 per cent of the
cetaldehyde . Only minute amounts escape
th e bloodstream. But that 's where th e
ro blem s sta rt .
The ave rage liver can pr ocess about 7grams
ethanol a n hour - tho ugh in heavy dr inkers
figure can rise to 10 gr a m s - mean ing that
Skeletal m uscle is particularly badly
affected. Preedy has found that rats given a
single dose of ethanol end up with significant
muscle da mage as a result of acetald eh yde
at tacking proteins.The changes persist for
mo re th an 24 hours , long after the che mica l
itself has disappeared from thesystem
(Alcohol andAlcoholism, vol 40. p 485). "It 'sa
common mi sconcept ion that the brain an d
th e liver are the two organ s mo st a ffected by
alcoh ol abuse," says Preedy. "Muscle damage
is th e most common." Among alco holics,h esays , mu scle da mage is five times more
common th an cirrhosis of th e liver.
To make matters worse, the immune
system see s these adducts as foreign an d fires
off an in flamma to ry response .Around.ro per
cen t of patients with alcoholic liver disease
have anti-acetaldehyde ant ibodies in th eir
bloodstream . Drumming up an inflammatory
response is usually considered a bad om en as
akes about 12 hours to eliminate all th e
hanol in a bottle of win e.That's 12 ho urs of
ontinuous exposure to acetaldehyde,
ssibly longer. " It remains to be so lved how
st ace taldehyde disappe ars," says alcohol
esearche r Peter Eriksson from Finland's
Public Health Institute in Helsinki.
rreversible damage
is becoming increasingly clea r is that
most anyex
posure toacetalde
hyde can dou s damage. Aceta ldehyde attaches itself
amino groups in proteins to for m stable
mpounds called adducts. According to On ni
em ela of th e University ofTarnp ere in
inland, th ese cause irreversible da mage by
up protein structure an clfunctio n .
th e wake ofa dr inki ng bout , a whole range
adducts are formed in th e liver, muscles,
art, bra in and gastrointestinal tract.
NewS(ientislllOFebruary2007
it can resu lt in cell in jury an d persisten t
in flammation . It has been linked with a ho st
of diseases, includ ing rheu m atoid arthritis,
he art attacks,Alzheim er 's disease a nd cancer
(New Scientist, 22 May 2004, p40).
Acetaldehyde also attacks DNA.In 2005,
researchers at the US Nat ion al Institute on
Alcohol Abus e and Alcoholism in Bet hesda,
Maryland , reported that acetaldehyde ca n
attack DNAin m uch th e sa m e way it does
pro tei ns.The res ulting adducts dis rup t DNA's
st ructur e
and function. an dcan triggerm utations and chromosomal prob lems
(Nucleic Acids Research. vol 33 p 3513). These
ad ducts have shown up in th e organs of
rodent s fed alcohol and also in the white blood
cells of alcoholics. Little wonder, then, that
although ethanolitself is not considered a
carcinogen.acetaldehyde is- atleast in animals.
The re is growing eviclence that
aceta ldehyde isa hu m an carcinogen too.
Some of the bes t evidence come s from studying
people who canno t process the compound
norm ally.Rough ly 50 per cent of people of
Japan ese ,Chinese, Korean or Taiwanese origin
carry at least one faulty copy of th e ALDH 2
gene and can scarcely break down
acetaldehyde at all.The mutation is dominant
so even having on e copy causes problems.
Flushed faces
The immediate co nseq uences of having th e
faulty version of the ALDH2 gene are highly
visible. "You can see it in any restaurant in
Japan or China," Eriksson says. Almost as soon
thes e people have an alcoholi c dr ink.t he ir
acetalde hyde levels shoot up to between 6 an d
20 times th at found in people with normal
ALDH2.This acetaldehyde "rush" trigge rs
facial t1ush ing,elevated he art rate and dilated
blood vess els. Dizziness, headache, nausea
and vo mi ting soo n follow.
Not surprisingly, most flushers tend to
avoid alcohol , which is just as well s ince th e
long-term health consequences ar c turning
ou t to be serious. Among the m inority offlushers who are also heavy drinkers, th e
incidence of upperga strointestinal tract
cancer is about 50 times the normal rat e.
Gen e-deficient people also have high rates of
hea d an d neck cancer.
There's mo re. A recent study of 818 heavy
dr inkers in Germany found that those
individuals who ar e exposed to m ore
acetaldehyde as a result of a genetic defect
in this case, in the gene for alcohol
dehydrogenase - are at greater r isk of
developing can cers of the upper
gastrointestinal tract an d liver (Interna tional
Ioutnal a/Cancer, vol na , p 1998).Th ese and aho st of other results all add to th e growing
suspicion th at acetald ehyde is a human
carcinogen, says Helmut Seitz, profess or of
alcoh ol research at the Univ ersity of
Heidelbergin Germany. Mikko Salaspuro,a
gastroenterolo gist at the Universi ty Central
Hospital of Helsinki.agrees. " It is likely tha t
acet aldehyde will soon be considered to be
carcinogenicin humans," he says.
Acetaldehyde also seems to play a role in
breast cancer. with up to 5 per cent of all breast
cancers attributa ble to a lcohol consumption.
"The cells don 't forget. This will ini tiate
tu m our s 20 to 25yea rs later,"
says Seitz, who isconvinced that esca lating alcoh ol in take in th e
west is linked to rising rates of liver, colon and
rectal cancer.
There arc even sugges tions of a link
between ace ta ldehyde and Alzheim er's
disease. In 20 04, researchers at Nip pon
Medical School in Kawasaki, japan, reported
that amon g a group of peo ple with
Alzhe imer's. the faulty version of ALDH2 was
www .newsrientist.rom
7/28/2019 Cheerz ATH NewScience
http://slidepdf.com/reader/full/cheerz-ath-newscience 4/4
gni ficantly mo re common than am ong a
en group of healthy peop le of
e same age (Annals of the New l'ork Academy
Sciences, vol 1011, P 36).
So who is at risk?As a general rul e, mo s t of
e excess acetaldehyde you encounter co me s
m alcoho l, and the more alcohol you drink
e m oreacetaldehyde you are exposed to.
no absolutely safe level of
m ptio n . "It is no t necessary to drink
am ou nt s of alcohol - even low amounts
et hanol taken regula rly in a sensitiven increases the ir risk." Seitz points out.
It 's a lso worth hearing in mind that m any
lic drinks conta in acetaldehyd e from
word go. Sherry producers, for instance.
ourage acetaldehyde product ion fo r its
y aroma. Calvados is particularly rich in
etaldehyde, and regular calvados dr inkers
ave twice th e incidence of oesophageal an d
al cancer compared with wine d rinkers who
sume the sam e amount of alcohol.
It gets worse. If you smoke , or are ex posed
ther people 's sm oke , you r acetaldehyde
rises furth er. Burning tobacco creates
dissolves in saliva, and
etaldehyde in saliva is a big problem. Unlike
e liver with its detoxifying enzyme s, the
mucous m em b ranes are pretty poor
breaking down acetaldehyde. Asa result,
toxic effect s persist for longer.
Among smoker s, the risk of oral cancer is
to 10 times higher than for people wh o have
There are , of course, downs of
gens in tobacco smoke, so
ldehyd e m ay well not be the on ly culprit.
ertheless , an individual smoker's cancer
s strongly as sociated with acetaldehyde
their saliva and some rese archers
ow believe th a t acetalde hyd e ma y be one of
e principal carcinogens in cigarette smoke .
Combine tobacco and alcoholand the
er multiplies. The effect is synergistic,
ing to Salaspuro,This could ex plain th e
-fold r ise in o ral cancers seen in people
o are both alco holics and smokers,
ed with those who ab stain fro m both .
don't know of any other cancers in which
e associations are so strong ,"Salaspuro says.
etaldehyde in saliva also comes from th e
tha t colonise th e mouth an d dig estive
ct. Many of these churn out acetaldehyde as
of their normal biochemistry. Others
ethanol from alcoholic drinks and turn
in to acetaldehyde.Some people harbour
rgan isms th at a re particularly good at
acetaldehyde. "It depends on the
of flora you h ave .There m ay be huge
at ions between individual s," says
aspuro. One mouth-dwelling bug,
ww.newscientisLcom
Strept ococcus salivarius, is particularly goo d at
tossing out acetaldeh yde. Another,Neisseria,
produces 100 ti m es more acetaldehyde when
exposed to ethanolcompared with ot her
m icroorganism s iso lated fro m the mouth.
Micro bial acetald ehyde produ ction coul d
also explain why people with poord en ta l
hygiene havean increased ris k of mouth
cancer.The Finnish researchers collected
saliva sam ples from 132 volunteers who
differed not on ly in their drink ing and
smoking habits but also in th e standardof their dent al hyg ien e. The result s show that
poor denta l hygiene comes with at wofold
increase in acetaldehyde leve ls (Oral
Oncology, vol 37p 153)·
Then t here is acet ald ehyde in th e diet. For
centur ies , peop les have used bacterial
fer me ntation to produce food -everything
from pickles an d yogur ts to bread and cheese.
Where th ere is fer m entation there is
Las t yea r the team released a study
showing tha t a piece of gu m containing jus t
5 mill igrams of t-cysteine could totally
eliminate acetaldehyde hom saliva if chewed
whil e smok ing (Cancer Epidemiology,
Biomarkers& Prevention , vol IS,p 146).
Salasp uro hopes the gum co uld help pr event
digestive tract cancers in those whoare most
at risk.The gu m is being com mercialise d by a
Finnish company ca lled Biohlt.
Germ -bu s ting mouthwash could also
help. Mouthwash contai ning the ant isepticchlorhexidine has be en shown to slash th e
numbers of acetaldehyde-p roducing
m icroo rganisms in t he mo u th , and in a st ud y
with 10 vo lunteers , the Finnish researchers
fo un d that t reatment with chlorhexidine for
th ree days cut acetaldehyde levels in drinkers '
saliva by 40 per cent.
i\nother solution proposed by th e Finnish
tea m is to tinkerwith th e bugs living in your
acetaldehyde. Acetaldehyde also occ urs
natu rally in r ipe fruit and coffee.
"Companies making da iry products
so meti mes try to increase the acetaldehyde
level to give it a specialaromat ic taste," says
Salaspuro, "Som e yog hur t producers are
searching for new bact eria that are even better
acetaldehyde p roducers." And if you live in a
city, there's more. Acetaldehyde is spewed out
by veh icle engines. Air pollution adds to the
to xic load, though no body is quite su re how
much this affects ou r health.
With ace ta ldehyde - and evidence of its
toxicity - coming at us from all sides, it 's not
surp rising that scientists are busy developing
ways to neutra lise the th reat. Salaspuroand
colleag ues at th e University of Helsinki , for
example, are developing a chewing gum tha t
mo ps up acetaldehyde.The gu m contain s a
harm less am ino acid , t-cysteine, wh ich reacts
with acetaldehyde and remo vesit from saliva.
intestines using preblotics or probiotics .
Lactulose - a ha rmless,indigestible sugar - is
one cand idate for th e job, says Salaspuro. In
experime nt s with rats , lactulosc appears to
inh ibit acetalde hyde production by m aking
th e colon more acidic.Alternatively,ingesting
a dose ofliving microorganisms that don 't
produce acetaldehyde, such as some
Lactobacillu s an d Bifidobact erium species,
cou ld als o help, say Seitz and Salaspu ro,
None of th ese interventions has been
shown to prevent cancer, so cannot as yet be
recommended as a substitute for a healthy
lifestyle. There is still only one sure route to an
acetaldehyde-free life : keep it clean. Scrub
yourteeth, avoid smoke,an d next time you 're
recovering from a ha ngover , remember to
promise your in ternal organs that this time
rea lly will be the las t. •
Lisa Melton isa science writerbased in London
10 February 10071 NewScientisllH