FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS	ESN:FAO/WHO/UNU/ EPR/81/35 August 1981
	WORLD HEALTH ORGANIZATION
	THE UNITED NATIONS UNIVERSITY

Provisional Agenda Item 3.3.2

Joint FAO/WHO/UNU Expert Consultation on
Energy and Protein Requirements

Rome, 5 to 17 October 1981

PROTEIN REQUIREMENTS FOR INFANTS, CHILDREN AND ADOLESCENTS

by

Kraisid Tontisirin
Ramathibodi Hospital and
Institute of Nutrition
Mahidol University
Bangkok

* Including 5 mg/kg/day for integumentary N-losses, NM = not measured

The factorial method based on the assumption that the obligatory N losses of 2 mg/basal kcal has been used as a major criterion for estimation of protein requirements in older infants and children of various age groups. For young infants under 6 months of age the method of direct measurement of protein intake particularly from breast milk and infant formula has been used (1). Since 1971, there have been some new data and concepts concerning the estimation of protein needs in children studied in both developed and developing countries (2–9). It is therefore the objective of this paper to review those informations.

Obligatory N-losses in infants and children

Recently, there were 3 reports of the study of obligatory N losses in infants and children (6,11–12) done in Taiwan and at INCAP. The data are shown in Table 1. As also compared to previous reports by Fomon et al (10) there was good agreement as to fecal nitrogen losses which were approximately 21 mg/kg/day. There were some differences of the urinary nitrogen losses which could be due to the age of the subjects, prior dietary protein intake and the actual protein intake during the study. The diets in the studies by Fomon et al, and Huang et al provided 12–28 mg N/kg/day, whereas the INCAP diets were virtually nitrogen free (11–12).

The total obligatory nitrogen loss was 1.43 mg/basal kcal in Taiwan study which was higher than the figure 0.67 mg/basal kcal of Fomon et al and much lower than the value of 2 mg/basal kcal adopted by the FAO/WHO Committee (1).

Since the value of obligatory N losses were quite low, in deriving the recommended protein intake, the adjustments for protein utilization and individual variation were made by 30 percent increases for each adjustment (1). Since there is another approach for estimating protein needs of children based on N-balance response which provides reasonably and better statistical calculation, the factorial method may be of less value (13). However the available data of obligatory N losses are useful for calculating true digestibility, BV and NPU of foods. Because of ethical problems and limited uses further studies of this type are undesirable (8).

Integumentary N-losses

The skin N loss studied with 12 Taiwanese infants given protein intake of 1.36 – 3.26 g/kg/day was 7.8 ± 2.9 mg/kg/day (6). This figure is very identical to the data from INCAP study with 4 preschool children given protein protein intake of 1.5 – 2.0 g/kg/day (10) When protein intake was zero, the integumentary N loss was 5 mg/kg/day and losses were increased to 6–7 mg/kg/day if protein intake was 0.5 g/kg/day (11).

Similar observations were noted in the study with preadolescent children. Fifteen healthy girls aged 8 to 9.5 years with average body weight of 28.9 kg had skin N losses of 7.0, 9.1 and 11.0 mg/kg/day when protein intakes were 1.2, 2 and 3 g/kg/day, respectively (14). The study with 12 boys aged 7.5 to 9.5 years showed almost identical data, the skin N losses were 6.7, 9.3 and 11.2 mg N/kg/day as correspended to protein intake of 0.94, 1.74 and 2.7 g/kg/day (15).

Based on the above data it is therefore reasonable to recommended that, in the interpretation of nitrogen balance studies on children who are not sweating, 8 mg N/kg/day be incorporated into calculation of nitrogen balance (9).

Growth and N-balance data

1. Infants

Initial study with an infant formula made from soy protein isolate fortified with methionine in 13 female infants from 8 to 111 days of age showed satisfactory weight gain of 25.5 g/day and normal serum values of urea nitrogen, total protein and albumin as compared from the data devived from the experiments with infants given either breast milk or cow milk based infant formula (3). Protein intakes were 1.86, 1.68 and 1.74 g/kg/day during the period of 8–41 days, 42–111 days and 8–111 days respectively. N-balance study conducted during the period of 113–118 days of age (almost 4 months old) in 6 infants given protein intake of 1.64 g/kg/day showed the mean apparent N retention of 101.8 mg/kg/day with the range of 63–125 mg/kg/day.

Subsequent study with 9 normal full term infants from 8 through 111 days of age fed a soy isolate base formula unsupplemented with L-methionine indicated lesser weight gain, lower serum albumin levels at age 28 days and greater serum concentration of urea nitrogen as compared to the data from study of 10 infants fed the same formula supplemented with L-methionine (6) and previous reported data of growth and serum chemical values of normal breastfed infants (5). Means of the apparent N retention studied with infants aged 67–307 days given protein intake of about 2.33 g/kg/day showed no statistical differences. The values of N retention ranged from 24–170 mg/kg/day (mean 120) and 87–203 mg N/kg/ day (mean 137) in infants fed unfortified formula and fortified formula respectively.

The results from these studies clear indicated protein requirements of the infants fed a fortifiedsoy isolate formula under 3 month of age for adequate growth and maintaining normal serum chemical values is approximately 1.7–2.3 g/kg/day. This value is slightly lower than the safe level of protein intake of 2.4 g/kg/day or recommended by the FAO/WHO Committee (1).

2. Children

The data from 1148 N-balance studies with 100 American boys and 23 girls 1 to 11 years given relatively high levels of protein intakes varied from 2.8 to 3.6 g/kg/days as commonly observed in habitual intake by children in the United States (4). The apparent N-retentions were strikingly high being 110, 90, 82 and 64 mg N/kg/day for the age groups of 12–18 months, 18–36 months, 3–6 years and 6–11 years, respectively.

Assuming that 20 percent of weight gain in children is body protein (1,2) and the growth rate in term of weight gain has been normal as expected (16). Nitrogen increments required by various age group would be:

The results from the studied by Ziegler and Fomon et al therefore can not be explained by the increment of N for growth and the data may not be applicable for making recommendation of safe level of protein intake.

The study with 15 preadolescent girls aged 8 to 9.5 years given 3 levels of protein intakes derived from a mixture of animal and plant sources with similar amino score to egg pattern indicated that based on true N-balance data, the protein requirement for those girls was almost 2 g/kg/day to have N retention of 10 mg/kg/day (14). Similar finding was noted in the study with 12 preadolescent boy 7.5 to 9.5 years that the need of protein was between 1.74 to 2.7 g/kg/day. The levels of protein requirements are higher than the current FAO/WHO recommendation. Since th data in this age group are very limited further study is needed.

3. Adolescents

The reports of studies of the protein requirements in adolescents are almost not existed (17). The recommendations on protein and amino acid needs therefore have been based the extrapolations between the data obtained with young infants and adult men and women (1). Even there is a “growth spurt” during adolescent period the calculated need of N for growth appeared little being only approximately 6 mg N/kg/day as previously described.

The N-balance response

The study with 8 mild malnourished Filipino boys 18 to 26 months old given habitual diet based on rice, fish vegetables and fruits with varying levels of protein intakes 0.75 to 2 g/kg/day. Energy intake was constant at 110 kcal/kg/day. The mean N requirement for maintenance was 112 mg/kg/day or 0.7 g protein/kg/day and the safe level of intake was 160 mg N/kg/day or 1.0 g protein/kg/day. Since the subjects had not been fully recovered from malnutrition the apparent N retentions were quite high even that during the study period some subjects had lost weight (18).

INCAP study with 10 children aged 17 to 31 months given protein from milk and soy isolate and energy intake of 100 kcal/kg/day using the N-balance response showed that the mean nitrogen requirements, allowing for integumental losses and growth were 98 mg (0.61 g protein) of milk/ kg/day and 120 mg (0.75 g protein) of soy isolate/kg/day. The milk requirement is 33 percent lower the recommendation by FAO/WHO Committee (19).

Subsequent studies with 4 children between 21 and 28 months of age given various levels of protein intakes provided by corn and black beans in a proportion of 76 and 24 percents indicated that the protein need by these children was 1.7 g/kg/day which was comparable for the safe level of intake of FAO/WHO after adjusting for protein quality.

The results from the above studies based on N-balance response method suggested that the protein requirements for preschool children at 1–3 years of age were in the same ranges or even lower than the safe level of intake recommended by the FAO/WHO Committee (1).

Effects of varying energy intakes on protein needs in children

Since the majority of the children in developing countries receive inadequate energy intake for the need as recommended by the FAO/WHO Committee (1), protein intakes may be utilized as energy source. At the meeting in Rome (21), it was agreed that there were two priority questions which should be tackled first.

1. Is the present “safe level” of protein intake adequate:

   1. at habitual levels of energy intake?

   2. at levels of energy intake which correspond with present estimates of energy requirements?

2. Would habitual protein intakes be adequate if energy intakes correspond to present estimates of energy requirements?

The data from the studies conducted in Thailand and at INCAP have been summarized in a report (8).

Nine children, aged 9 to 36 months, weighing 8.1 to 11 kg were given Thai habitual diets at 3 levels of energy intakes varying from 87–118 kcal/kg/day. Each level of energy intake lasted for 7 days.

The protein intake was fixed at the safe level, 1.7 g/kg/day derived from rice and fish in the ratio of 70:30, and having amono acid score of 94.8 with assumed digestibility of 93 percent.

At the lowest level of energy intake of 87 kcal/kg/day apparent N-retention and weight gain were 43.7 mg/kg/day and 3.5 g/day, respectively. At the two higher levels of energy intake (100 and 118 kcal/kg/day), apparent N retention was greater than 60 mg/kg/day and weight gain was greater than or about 20 g/day.

B.V. and NPU were significantly decreased with the decreases in energy intakes. N absorption and true digestibility however, were not affected by the changes in energy intakes, approximately 60 and 68 percent, respectively. The results from this study suggested that the safe level of protein intake as recommended by FAO/WHO in 1973, the Thai habitual weaning food provided adequate protein for the need of young children if energy intake was adequately supplied at 100 kcal/kg/ day or higher.

The INCAP study with 6 children 23–40 months old given cornbeans based diets and 3 levels of energy intakes showed similar results that the level of protein intake of 1.75 g/kg/day derived from corn and beans was adequate for the children when energy intake was adequate.

The only discrepancy between the Thai and INCAP studies is the effects of decreases in energy intakes on BV and NPU since the INCAP study did not reveal any effects. A possible explaination is that the subjects in the Thai study were younger than the group studied at INCAP.

Another report from the study with 4 Indian preschool children 3.5 to 4.5 years old using similar protocol of the experiments also confirmed the conclusion that at adequate energy intake the protein requirement of the subjects was 1.33 g/kg/day which is equivalent to the safe level of protein intake 22).

Since there have been questions about the relevant of the findings from short term studies to the real life situation, a long term study was conducted in 6 male infants, aged 8–12 month given Thai habitual diet providing protein and energy intake approximately 1.7 g and 100 kcal/kg/day for 4 months. The results based on N retention measured monthly, weight gain, observation of physical activities and measurements of blood constituents indicated that this “safe level” of protein intake was also adequate if energy intake was adequately supplied 23).

The question whether the habitual diets provide adequate protein needs of pre-school children with adequate energy intakes was tackled by the INCAP study with 11 boys 29 to 46 months old. The diets were food commonly consumed by the Gutemalen children. It was concluded that with the diets used in the study, protein intakes were adequate when energy intakes corresponded to the estimates of energy requirements and the protein and energy needs of well nourished children were satisfied by the diets used in this study if : (a) dietary density was increased, and (b) sufficient amounts of the staple foods were available 24).

Conclusions

Since 1971, more data on protein requirements are still limited to infants and preschool children at 1–3 years of age, with a few studies with the preadolescents and adolescents.

The direct measurement of food intake, growth and N-retention data in the studies with infants and preschool children indicated that the “safe level” of protein intake, recommended by the FAO/WHO in 1973 are adequate if energy intakes are adequately provided. Long term study also confirmed this conclusion.

More studies in a normal living situation on a long term basis are needed as well as the studies with pre and adelescent children. Functional criteria for assessing protein and energy needs should also be further explored.

References:

1. Joint FAO/WHO Ad Hoc Expert Committee. Energy and Protein Requirements. WHO Technical Report Series No. 522. Geneva: World Health Organization, 1973.

2. Foman, S.J. Infant Nutrition, 2^nd edition. W.B. Saunders Co Philadelphia, 1974

3. Fomon, S.J., Thomas, L.N. Filer, L.J., Jr., Anderson, T.A. and Bergman, K.E. Requirements for protein and essential amino acids in early infancy.Acta Paediat. Scand. 62:33–45, 1973.

4. Ziegler, E.E., O'Donnell, A.M., Stearns, G., Nelson, S.E., Burmeister, L.F. and Fomon, S.J. Nitrogen balance studies with normal children. Am. J. Clin. Nutr. 30:939–946, 1977.

5. Fomon, S.J., Ziegler, E.E., Filer L.J., Jr., Anderson, T.A., Edwards, B.B. and Nelson, S.E. Growth and serum chemical values of normal breast fed infants. Acta Paediat. Scand. Suppl. 273, 1978.

6. Fomon, S.J., Ziegler, E.E., Filer, L.J., Jr., Nelson, S.E. and Edwards B.B. Methionine fortification of a soy protein fed to infants. Am. J. Clin. Nutr. 32: 2460–2471, 1979.

7. Huang, P.C., Lin, C.P. and Hsu, J.Y. Protein requirements of normal infants at the age of about 1 year: maintenance nitrogen requirements and obligatory nitrogen losses. J. Nutr. 110:1727–1735, 1980

8. FAO/WHO. Report on the informal gathering of investigators to review the collaborative research programme on protein requirements and energy intake (FAO 16–18 January 1980), Rome.

9. UNU - World Hunger Programme, Food and Nutrition Bulletin Supplement 5. Protein-Energy Requirements of Developing Countries : Evaluation of New Data, 1981.

10. Fomon, S.J., DeMaeyer, F.M. and Owen, C.N. Urinary and fecal excretion of endogenous nitrogen by infants and children. J. Nutr. 85:235–246, 1965.

11. Viteri, F.E. and Martinez, C. Integumental nitrogen losses of pre-school children with different levels and sources of dietary protein intake. In Protein-Energy Requirements of Developing Countries : Evaluation of New Data, edited by Torun, B., Young, V.R. and Rand, W.M. UNU-World Hunger Programme, Food and Nutrition Bulletin Supplement 5 : 164–168, 1981.

12. Torun, B. and Viteri, F.E. Obligatory nitrogen losses and factorial calculations of protein requirements of pre-school children. In Food and Nutrition Bulletin Supplement 5: 159–163, 1981.

13. UNU-World Hunger Programme, Food and Nutrition Bulletin Supplement 1. Protein-Energy Requirements under Conditions Prevailing in Developing Countries : Current Knowledge and Research Needs, 1979.

14. Howat, P.M., Korslund, M.K., Abernathy, R.P. and Ritchey S.J. Sweat nitrogen losses by and nitrogen balance of preadolescent girls Consuming three levels of fietary protein. Am. J. Clin. Nutr. 28:879–882, 1975.

15. Korslund, M.K., Leung, E.Y., Meiners, C.R., Crew, M.G., Taper, J., Abernathy, R.P. and Ritchey, S.J. The effects of sweat nitrogen losses in evaluating protein utilization by preadolescent children. Am. J. Clin. Nutr. 29: 600–603, 1976.

16. Vaughan V.C. III. Growth and development. In Nelson Textbook of Pediatrics 10^th edition by Vaughan, V.C. III. and Mckay, R.C., W.B. Saunders Co. Philadelphia pp. 13–51, 1975.

17. Hegsted, D.M. Current knowledge of energy, fat, protein and amino acid needs of adolescents. In Nutritional Requirements in Adolescence, edited by McKigney and Munro, H.M., M.I.T. Press, pp. 107–126, 1973.

18. Intengan, C.L., Roxas B.V., Loyola, A. and Carles, E. Protein requirements of Filipino children 20 to 29 months old consuming local diets. In Food and Nutrition Bulletin Supplement 5: 172–180, 1981

19. Torun, B. Cabrera-Santiago, M.S. and F.E. Viteri. Protein requirements of pre-school children : Milk and soybean protein isolate. In Food and Nutrition Bulletin Supplement 5: 182–190, 1981.

20. Viteri, F.E., Torun, B., Arroyave, G. and Pineda O. Use of cornbean mixtures to satisfy protein and energy requirements of preschool children. In Food and Nutrition Bulletin Supplement 5: 202–209, 1981.

21. FAO/WHO. Energy Intakes and Protein Requirements. Report of the First Joint FAO/WHO Expert Consultation. FAO, Rome, 1978.

22. Iyengar, A.K., Narasinga, B.S. and Reddy, V. Effect of varying protein and energy intakes on nitrogen balance in Indian preschool children. Br. J. Nutr. 42: 417–423, 1979.

23. Tontisirin, K., Ajmanwra, N. and Valyasevi, A. Long term study on the adequacy of Thai habitual weaning food in young children. A report of phase 2 study submitted to FAO/WHO 1981.

24. Torun, B. and Viteri, F.E. Capacity of habitual Guatemalan diets to satisfy protein requirements of pre-school children with adequate dietary energy intakes. In Food and Nutrition Bulletin Supplement 5: 210–228, 1981.