document resume ed 115 590 institution md.*adolescent nutritional requirements. abstract. 0 it is...

DOCUMENT RESUME

ED 115 590 SP 009 659

AUTHOR McKigney, John I,; Munro, Hamish N.TITLE Nutrient Requirements in Adolescence.INSTITUTION National Institutes of Health (DHEW), Bethesda,

Md.REPORT NO DHEW-NIH-76-771PUB DATE 75NOTE 17p.

EDRS PRICEDESCRIPTORS

IDENTIFIERS

MF -$O.76 HC-$1.58 Plus Postage*Adolescence; Adolescents; Eating Habits; HealthEducation; *Nutrition; Nutrition Instruction*Adolescent Nutritional Requirements

ABSTRACT0 It is important to understand the nutrientrequirements and the significance of nutrition both in pubescence andadolescence. The pubescent growth spurt is characterized by anincrease in body size and a change in p-oportion of differenttissues. Both of these factors are of great nutritional importance,since there is reason to believe that the growth spurt is sensitiveto nutrient deprivation, although our knowledge of the requirementsof adolescents for various nutrients is incomplete. The Food andNutrition Board of the U.S. Academy of Sciences has publishedsuccessive issues of its "Recommended Dietary Allowances (RDA) . "TheTen-State Nutrition Survey (1968-70)," which measured food intake oflover income fa :ilies in the United States, shows deficits amongadolescents whel, compared with the RDA. The dietary inadequacies ofadolescents may sometimes be accentuated by situations causing extrademands for nutrients, such as pregnancy, injuries, and involvementin sports. Excessive intake of nutrients also occurs duringadolescence; one of the most common conditions due to an imbalancebetween food intake and expenditure is obesity. Excessive intake ofdietary fat, notably saturated fat, has been associated with elevatedblood cholesterol levels. Studies have indicated that the onset ofboth atherosclerosis and obesity may well occur during childhood, andthat the most appropriate time to apply preventative measures and toprovide nutritional education is during adolescence. (BD)

***********************************************************************Documents acquired by ERIC include many informal unpublished

* materials not available from other sources. EPIC makes every effort ** to obtain the best copy available. Nevertheless, items of marginal *

* reproducibility are often encountered and this affects the quality *

* of the microfiche and hardcopy reproductions EPIC makes available* via the ERIC Document Reproduction Service (EDRS). EDRS is not* responsible for the quality of the or:l.ginal document. Reproductions ** supplied by EDRS are the best that can be made from the original.***********************************************************************

e 8 141 w

nutrient requirementsin adolescente

John I. McKigney and Hamish N. Munro

U S MEN, OF HEALTH.EDUCATION £ WELFARENATIONAL INSTITUTE OF

EDUCATION

THIS DOCUMENS HAS BEEN REPRO-OUCED EXACTLY AS RECEIVED FROMTHE PERSON OR ORGANIZATION ORIGIN-ATING IT POINTS OF VIEW OR OPINIONSSTATED DO NOT NECESSARILY REPRE-SENT OFFICIAL NATIONAL INSTITUTE OFEDUCATION POSITION OR POLICY

(John I. McKigney is Health ScientistAdministrator with the Growth and Development

Branch of the National Institute of Child Healthand Human Development, National Institutes of

Health. Hamish N. Munro is Professor ofPhysiological Chemistry with the Department

of Nutrition and Food Science at theMassachusetts Institute of Technology.)

DHEW Publication No. (NIH ) 76-771

Considerable research effort in recent years hasyielded solid rewards in the form of a much betterunderstanding of nutrient needs during infancyand early childhood. In contrast, the significanceof nutrition in development in later childhood andadolescence is not yet as clearly understood.

There are many clues to unanswered questionsabout how nutrition may be implicated in phe-nomena associated with adolescence. For ex-ample, the final mature height of American-bornand -reared Japanese is greater than that of Japa-nese natives. Does this difference represent thebenefits of a more abundant supply of nutrientsduring infancy or during the later growing period?

43

Autopsies on young American battle casualtiesduring the Korean War revealed considerabledeposition of fat in the wall of tne aorta. At whatstage of growth and adolescence does such depo-sition take place, and is the adolescent. diet acausal factor in this precursor of atherosclerosis?What are the implications of the changing dietaryhabits and fads to which the adolescent is in-clined? Also, is it nutritionally more demandingto be an adolescent mother than to be an adultmother?

In order to answer some of these questions, andto assess our present state of knowledge of theoptimum levels of nutrients for the adolescent, a

conference* was held in June, 1973, at whichsome fifty scientists representing nutrition, anthro-pometry, clinical endocrinology, pediatrics andrelated biomedical fields pooled their experience.The following discussion of the nutrient needs ofthe adolescent is primarily based on the conclu-sions emerging from that meeting and the pub-lished proceedings (1).

Strictly speaking, pubescence is the correct termfor the period of sexual development ending withthe emergence of the capacity for sexual repro-duction. On the average, this occurs at about 15

years for boys and 13 years for girls. The termadolescence is correctly applied to the period ofgrowth after this time, that is, from a mean age of15 to 21 years for boys and 13 to 17 years forgirls (2).

When discussing nutrient requirements, both peri-ods should be included in adolescence. Thegrowth spurt associated with pubescence imposesimportant additional requirements about,which weknow too little. Furthermore the time of sexualmaturity varies widely in individuals, so that some10-year-old girls have already entered pubescence

The conference was one of a series being sponsored by theGrowth and Development Branch. National Institute of ChildHealth and Human Development, to focus attention on pubertyand adolescence. and to define research areas which deservepriority attention in an expanded effort to broaden our knowl-edge of adolescent development. Those who contributed tothe conference. in addition to the present authors. included:William R. Beisel. Mary Blackburn. Jo Anne Brasel. James P.Carter, C.-Frank Consolazio. David B. Coursin. Mary C. Egan,Jordan W. Finkelstein, Gilbert B. Forbes, Hortense Gandy,

Dale C. Garell, Peter V. Hamill, Felix P. Hedld, L. Mark':egsted, Ray Hepner, Robert Hodges, Malcolm A. Holliday,M. Isabel Irwin, Harry L. Jacobs. Herman L. Johnson, FrancisE. Johnston, Jerome L. Knittle, James H. Leathem, Frank W.Lowenstein, Rill( Luyken, Robert Malina, Karl E. Mason,William J. McGanity, William M. Moore, John F. Mueller,Merrill S. Read, Sanford J. Ritchey, Alexander F. Roche,Harold H. Sandstead, Howerde Sauberlich, Arnold E. Schaefer,B. G. Shah, Angus M. Thomson, Frederick Trowbridge,Charlotte M. ioung, Vernon R. Young.

4

while some 14-year-old boys are just beginning toshow signs of sexual development. Consequently,this discussion deals with nutritional needs duringthe continuum from 10 years of age until growthceases.

The pubescent growth spurt is characterized byan increase in body size which attains a ratematched or exceeded only by the developing fetusand infant in the first year of life. This growthspurt occurs earlier in girls and is less extensivethan for boys, so that the relative heights andweights of boys and girls change more than onceduring the growing period. This has recently beendocumented for the United States in a uniqueseries of publications of the National Center forHealth Statistics, based on measurements madeon large groups carefully chosen to be represen-tative of the population. The Health ExaminationSurvey was carried out between 1962 and 1970.These data show that girls are taller and heavierthan boys from about 9 to 131/2 years of age, afterwhich the situation is reversed. The report also

shows that black boys are taller than white boysuntil 9 years of age, whereas from age 14- on,white boys are taller than black boys. However,the weight of white boys is never less than that ofblack boys (3). Are these differences genetic ornutritional in origin?

Of even greater nutritional importance is thechange in proportion of different tissues during thepubescent growth spurt. In the pre-pubescentyears, the proportions of lean and fat tissue areabout the same for boys and girls. During thegrowth spurt, however, girls gain proportionatelymore fat than lean tissue, and retain this ratioduring the rest of growth. In contrast, boys acquireless fat and have a greater and more sustainedgain in lean body mass (4). In fact, boys on anaverage gain about twice the amount of lean tissuegained in girls. Because this gain in bone andmuscle is accompanied by increased tissue depo-sition of protein and such minerals as iron andzinc and calcium salts, one can predict that thepuberty growth spurt of the male must make more

ti

dietary demands for protein, iron, zinc and cal-cium than does the growth spurt of the girl. It hasbeen shown that the number of red blood cellsof boys rises considerably during pubescence,whereas that of girls remains constant (5). Thegreater demand for iron for synthesis of red bloodcells and formation of increased musculature canbe correlated with the more frequent occurrenceof anemia in pubescent males than females inlower income groups (6).

Is there any reason to believe that the growthspurt is sensitive to nutrient deprivation? Evidenceof both a general and a specific character suggeststhat this may be so for populations on marginalfood intakes. For example, preliminary examina-tion of survey data being assembled in somedevelopihg countries with a high incidence of mal-nutrition in children suggests that little or nogrowth spurt occurs in adolescents (7). Similarly,records of the growth of Japanese schoolchildrenextending over the past forty years or more showthat the growth spurt was delayed and smallerduring World War II; since then it has gradually

returned to pre-war patterns and currently ex-ceeds pre-war levels (8). It is not known whethermalnutrition during infancy is responsible for thefailure to have a normal growth spurt at pubes-cence, or whether the nutritional effect is a directone at the time of the growth spurt.

Our knowledge of the requirements of adolescentsfor various nutrients is incomplete. One reason forthis is that man seems to be the only animal show-ing a growth spurt, and experimentation on hu-mans is both difficult and often unethical. TheFood and Nutrition Board of the U.S. NationalAcademy of Sciences has published successiveissues of its Recommended Dietary Allowances(RDA), including those for adolescent boys andgirls (9). Although these estimates of needs arebased on many pieces of evidence, they can onlybe regarded as approximations. Boys 11-14 yearsold are allowed 2800 calories per day, rising to3000 calories per day for the 15-18 age group.This latter allowance is greater than the energyintake allocated to the mature adult male. In con-trast, girls aged 11-14 are allotted 2400 calories,

declining to 2100 calories for ages 15-18. Thisdifference in recommended allowances presum-ably reflects the later, larger and more prolongedgrowth spurt of males. However, the estimated pro-tein requirements of the two sexes does not fullymirror this pattern for energy intake because therecommended intake of protein for the femaletends to increase even when the energy allowanceis decreasing. The Ten-State Nutrition Survey,1968-1970, which measured food intake of lowerincome families in the U.S., shows deficits amongadolescents compared with the RDA. The surveydata (10) show that energy intake of white maleadolescents was adequate, while that of whitefemale adolescents was below the recommendedlevel for their age. Energy intakes of black adoles-cents of both sexes were well below recommendedlevels. Data of the Health Examination Surveymentioned earlier show that white boys are tallerand heavier than black boys from 14 years of ageon. Thus, results of the two surveys are in agree-ment and suggest a nutritional basis for these

differences in height and weight of adolescentmales.

The Ten-State Survey also revealed deficits in theintakes of vitamin A, riboflavin, calcium and ironby adolescents, when compared with their recom-mended allowances. This can be correlated withclinical evidence of certain deficiency conditionsamong this group (11). Direct evidence of growthretardation associated with these suboptimal nu-trient intakes emerges from a more detailed analy-sis of the Texas portion of the Ten-State NutritionSurvey (12). Failure to find evidence in the past-ofmalnutrition as a factor in adolescent growth anddevelopment has probably been due to dilution ofthe data from low income groups with data from thewealthier majority of the population. Similarly, thebenefits of better nutrition for fetal developmenthas only recently become evident when attentionwas concentrated on specific poorer segments ofthe U.S. population (13). These various observa-

--tions, though somewhat imprecise, as population

studies tend to be, clearly indicate that somesegments of the adolescent population in theU.S. are receiving inadequate intakes of certainnutrients.

The inadequacies may sometimes be accentuatedby situations causing extra demands for nutri-entsfor example, an adolescent pregnancy.Pregnancy in the adolescent appears usually notto be associated with competition between motherand child for nutrients (14). However; some in-vestigators feel that marginal intakes of vitaminA, iron, calcium and trace minerals may makesome adolescent mothers vulnerable to deficiencywhich, in the case of vitamin A, may be a contribu-tory factor in producing birth defects in her unbornchild (15). Studies on pregnant black teenagers inCalifornia (16) suggest that the recommendedallowance of calories is substantially low, espe-cially since it is now recognized (17) that theoutcome of pregnancy may be improved by higher

energy intakes than those previously consideredadequate. The old notion that the unborn child isimmune to malnutrition is being seriously ques-tioned in light of recent studies which correlatebirth weight with nutritional status of the mother.In future research in this area, special attentionshould be paid. to the adolescent mother and theeffects of nutrition on her own health as well ason that of her unborn child.

Other forms of stress also increase the demandsof the adolescent for nutrients. In response toinfection and to injury, the principal initial needsappear to be for adequate supplies of energy andamino acids in order to reduce wastage of tissuesand to encourage rapid convalescence and re-placement of tissue losses (18). The well-nourishedadolescent is better able to meet such stresses.

Nutrition of the adolescent actively involved insports is also beginning to receive serious con-sideration. Weight reduction of adolescents tomeet requirements for certain sports by restrict-

:1

ing food and fluid intakes is commonly practiced,the latter usually shortly before a contest (19).This can adversely affect the health and well-beingof the growing adolescent. Water deprivation, par-ticularly, may be responsible for collapse and evendeath of athletes during the stress of the game.

What has been said so far has dealt with recom-mended allowances of nutrients and evidence ofgroups in the U.S. population whose diets maynot be meeting these recommended levels. How-ever, excessive intakes of nutrients also occur inadolescence. One of the most common conditionsdue to an imbalance between food intake andexpenditure is obesity, much of which stems fromearly childhood.

Studies on the number of fat cells in the bodysuggest that the normal person ceases to add fatcells to his or her body between the ages of 2and 10 years, and then resumes production of newfat cells during puberty (20). Thus the normalchild shows a pubertal increase in body fat as

well as a general adolescent growth spurt. Incontrast, the obese-prone child continues :to addfat cells to his body during the whole of his first10 years and thus enters adolescence with anabnormally large number of such cells which arealso larger in size than those of non-obese chil-dren. Such fat cells demand to be fed and divertsome of the energy intake to deposition of furtherbody fat, reflecting an abnormal metabolic -statewhich tends to persist through adulthood.

Excessive intakes of dietary fat, notably saturatedfat, have been linked to atherosclerosis associatedwith elevated blood cholesterol levels. Youngadults demonstrate fatty streaks in the lining oftheir blood vessels which ae probably precursorsof irreversible arterial damage. Studies on boys

in a residential school showed a tendency to ele-vated levels of blood cholesterol which could besignificantly reduced by lowering the total fat con-tent of their diet and raising the unsaturated fatcontent (21). The blood cholesterol levels roseagain when the boys returned to their home dietsduring the vacation. This implies that the onsetof future atherosclerosis may well occur duringchildhood and, moreover, that the most appro-priate time to apply preventive measures and toprovide nutritional education is during adoles-cence. These two problemsatherosclerosis andobesityraise the question of whether thereshould be a recommended dietary maximum as.well as a recommended dietary, allowance foisome nutrients.

1O

what does future promise in studies ofadolescent nutrition?

Future studies of the nutr.i:on of adolescentsshould be performed by more sophisticatedand comprehensive procedures, including theuse of bone growth measurements whichindicate the developmental as well as thechronological age of the individual. Combinedsurveys involving biochemical and clinicalmeasures of fitness and deficiency as wellas bone age measurements should yield aclearer definition of the .state of nutrition ofthis age group in the population.

More detailed study should be made of thepubertal growth spurt to refine estimates of

itrient requirements during this period ofrapid change in body composition. Attentionshould be given to the potential developmentof individual dietary requirements for adoles-cents whose growth spurts vary consider-ably from the norm. Such studies should take

11

into account not only the relationship ofnutrient intakes to weight and height changes,but also correlation of body composition andsexual characteristics with plasma hormonelevels.

The food habits of teen-agers need syste-matic exploration, including investigation ofthe effect of alcohol, drugs and steroid con-traceptives on intake and utilization of nutri-ents. The immediate and long-term effectsof "fad" diets, including those for rapid lossor gain in weight, need to be considered.

The identification of specific medical groupsincluding adolescents with obesity, diabetesand elevated blood cholesterol levels shouldbe followed by studies of the impact of nutri-tion on their future health and of means ofchanging their dietary habits for the better.

More basic information is needed about manyaspects of adolescent development. There areindications that the maximum genetic c ipacityfor adult stature has been reached in the U.S.,whereas adult weight attained is still increasing.Research is needed to determine if this impliesan increasing tendency towards adult obesity. Therelationship between body composition of theadolescent and the incidence of illness and mor-Iity in later life has yet to be explored. This in-

formation would be helpful in determining optimalobjectives for adolescent nutrition. Finally, thereis evidence from studies on rats (22) that thecapacity to secrete growth hormone during the

whole growing period can be affected by mal-nutrition of the fetus due to an inadequate mater-nal diet. It may be that the growth spurt of thehuman is also, to some extent, determined bynutrition in the uterus and in early post-natal life.All these research objectives are not only desir-able but also urgent, considering the fact thatfoods in this country are increasingly engineeredand processed for mass consumption. The pro-ductiveness, well-being and longevIty of the futureadult population may be enhanced by the answersto these questions regarding nutrition during theadolescent _period of life.

12

references

.*-

13

1. McKigney, J. I. and Munro, H. N.(Eds.): Nutrient Requirementsin Adolescence. Cambridge,Mass., MIT Press, 1975.

2. Roche, A., conference proceed-ings, pg. 33

3. National Center for Health Sta-tistics: Height and Weight ofChildren. United States. Vitaland Health Statistics. D.H.E.W.Pub. No. 1000series 11No. 104.

4. Cheek, D. B. Human Growth.Philadelphia, Pa., Lea andFebiger. pg. 247. 1968.

5. Daniel, W. A. Hematocrit: matu-rity relationship in adoles-cence. Pediatrics; 52: 388-394. 1973.

6. Hepner, R., conference proceed-ings, pg. 171

7. Thomson, A. M., conference pro-ceedings, pg. 349

8. Munro, H. N. Report of a con-ference on protein and aminoacid needs for growth anddevelopment. Am. J. Clin.Nutr., 27: 55-58. 1974.

9. Food and Nutrition Board, Na-tional Academy of SciencesNational Research Council.Recommended Dietary Allow-ances, Eighth Edition. 1974

10. Hegsted, D. M., conference pro-ceedings, pg.109

11. Hodges, R. E., conference pro-ceedings, pg. 130

12. McGanity, W. J., conference pro-ceedings, pg.157

1 4

13. Winick, M., private communic4tion.


15. Hodges, R. E., conference pro-ceedings, pg.131

16. Blackburn, M., conference pro-ceedings, pg. 280

17. World Health Organization: Tech-nical Report series No. 522.Energy and Protein Require-ments. Report of a joint FAO/WHO ad hoc Expert Commit-tee. Geneva. 1973.

18. Beisel, W. R., conference pro-ceedings, pg. 259

19. Consolazio, C. F., conferenceproceedings, pg. 214

20. Knittle, J., conference proceed-ings, pg.83

J 5

.


22. Shrader, R. E. and Zeman, F. J.In vitro synthesis of anteriorpituitary growth hormone asaffected by maternal proteindeprivation and post-natal foodsupply. J. Nutr., 103: 1012-1017. 1973.

16

references 1. McKigney, J. I. and Munro, H. N.(Eds.): Nutrient Requirementsin Adolescence. Cambridge,Mass., MIT Press, 1975.

2. Roc:ie, A., conference proceed-ings, pg. 33

3. National Center for Health Sta-tistics: Height and Weight ofChildren. United States. Vitaland Health Statistics. D.H.E.W.Pub. No. 1000 series 11No. 104.

4. Cheek, D. B. Human Growth.Philadelphia, Pa., Lea andFebiger. pg. 247. 1968.

5. Daniel, W. A. Hematocrit: matu-rity relationship in adoles-cence. Pediatrics; 52: 388-394. 1973.

14

6. Hepner, R., conference proceed-ings, pg. 171


8. Munro, H. N. Report of a con-ference on protein and aminoacid needs for growth anddevelopment. Am. J. Clin.Nutr., 27: 55-58. 1974.

9. Food and Nutrition Board, Na-tional Academy of SciencesNational Research Council.Recommended Dietary Allow-ances, Eighth Edition. 1974



12. McGanity, W. J., conference pro-ceedings, pg.157

13. Winick, M., private communica-tiun.



16. Blackburn, M., conference pro-ceedings, pg. 280

17. World Health Organization: Tech-nical Report series No. 522.Energy and Protein Require-ments. Report of a joint FAO/WHO ad hoc Expert Commit-tee. Geneva. 1973.

18. Beisel, W. R., conference pro-ceedings, pg. 259

19. Consolazio, C. F., conferenceproceedings, pg. 214

20. Knittle, J., conference proceed-ings, pg. 83

.1 5


22. Shrader, R. E. and Zeman, F. J.In vitro synthesis of anteriorpituitary growth hormone asaffected by maternal proteindeprivation and post-natal foodsupply. J. Nutr., 103: 1012-1017. 1973.

DISCRIMINATION PROHIBITED Title VI of the Civil Rights Act of 1964states: "No person in the United States shall, on the ground of race, color, sex,age, or national origin, be excluded from participation in, be denied the benefitsof, or be subjected to discrimination under any program or activity receivingFederal financial assistance," Therefore, the National Institute of child Healthand Human Development, N1H, PHS, like every program or activity receivingfinancial assistance from the Department of Health, Education, and Welfare,must be operated in compliance with this law.