Protein and Energy Requirements in Infancy and Childhood

Some 30 years ago, Günter Dörner stated that the concentrations of hormones, metabolites and neurotransmitters during critical periods of early development will program disease risk in human adulthood, a concept that since has received enormous scientific support and broad attention. Evidence has also accumulated showing that early nutrition programs later obesity risk.

The energy requirements of infants and children are defined as the amount of food energy needed to balance total energy expenditure (TEE) at a desirable level of physical activity, and to support optimal growth and development. New TEE data from doubly labeled water and heart rate monitoring are available to derive the energy requirements. Compared with the 1985 FAO/WHO/UNU recommendations, the 2004 FAO/WHO/UNU and 2002 IOM recommendations are ~12–20% lower during infancy. The 2004 FAO/WHO/UNU recommendations are on average 18% lower for boys and 20% lower for girls 7 years of age, and 12% lower for boys and 5% lower for girls 7–11 years of age. From 12 to 18 years of age, the requirements are 12% higher for boys and girls. The 2002 IOM recommendations are 8% lower for children 7 years of age, 2% lower for children 7–11 years of age, and 8% higher for children 12–18 years of age.

During the last 35 years there have been various published assessments of human protein needs, including those of infants and children. Most recently, the Institute of Medicine of the US National Academies has published its report on Dietary Reference Intakes (DRI) for Macronutrients, and WHO/FAO/UNU have convened a new Expert Consultation, which is due to be published soon.

Growth and nutrition during infancy are being viewed with renewed interest because of the possibility that they may be linked to cardiovascular and metabolic health in later life. Of particular interest are differences between breast- and formulafed infants with regard to nutrient intake and growth because breastfeeding has been shown to be associated with a reduced risk of obesity in later life. During the first 6–8 weeks of life there is little difference in growth (gain in weight and length) between breast- and formula-fed infants. However, from about 2 months of age to the end of the first year of life formula-fed infants gain weight and length more rapidly than breast-fed infants.

Knowledge of changes in body composition is of great potential benefit to the understanding of the nutritional needs and functional outcome of nutritional management for both healthy and sick infants. This review evaluates the different methods presently available to evaluate whole-body composition analysis based on different models, i.e. 2, 3, or more compartments.

Nutrient reference values provide guidance for maintaining and enhancing health via standard setting and development of nutritionally improved products to decrease the risk of disease. Since 1941, the Food and Nutrition Board (FNB) of the National Academy of Sciences in the United States has developed and periodically revised recommendations for nutrients; the last (10th) edition of the Recommended Dietary Allowances (RDA) was released in 1989.

The portal-drained viscera (stomach, intestine, pancreas and spleen) have a much higher rate of both energy expenditure and protein synthesis than can be estimated on the basis of their weight. A high utilization rate of dietary nutrients by the portal-drained viscera might result in a low systemic availability which determines whole-body growth. From studies in our multiple catheterized piglet model, we conclude that more than half of the dietary protein intake is utilized within the portal-drained viscera and that amino acids are a major fuel source for the visceral organs.

Nitrogen balances have been conducted in preterm infants, preschool children, and 6- to 10-year-old children to determine dietary indispensable amino acid. A recent review concluded that the data, being sufficiently uncertain, could not be used as the basis for defining amino acid requirements in infants and children. Therefore, it was decided to use a factorial approach (basal plus growth).

Among other nutrients of breast milk, the amino acid pattern is considered normative throughout infancy. Exclusive breastfeeding by a healthy mother should be the standard from birth to 6 months. During the breastfeeding period the protein intake is low in the human being compared too many other animals.

Food intake is regulated in both the short- and long-term by a complex physiological system that involves neuroendocrine pathways that are both distinct and overlapping. The underlying causes and mechanisms of the dysregulation of food intake in obesity is poorly understood; however, it is clear that dietary components interact with the physiological determinants of food intake and can cause profound alterations during the development of control mechanisms.

The possible role of early dietary habits as the origin of later consequences on health has raised questions on the optimal macronutrient intakes of the growing infant. Infants and toddlers in developed countries usually show a high dietary protein: energy ratio during the complementary feeding period, averaging 2.5–3, because of the protein density of solid weaning foods and the low percentage of mothers still breastfeeding beyond the first 6 months of life.

In 2001, a WHO Expert Consultation concluded that waiting until 6 months to introduce complementary foods to breastfed infants confers several benefits for both infants and mothers. Nonetheless, there is still controversy about this issue. In developing countries, the reduced risk of infant gastrointestinal illness and increased duration of maternal lactational amenorrhea associated with exclusive breastfeeding for 6 months make the benefit-risk ratio of this recommendation highly favorable. In industrialized countries, the case is less clear-cut, but the benefit-risk ratio is also likely to be favorable with regard to infant infectious morbidity, motor development and maternal weight loss postpartum.

Thirty years ago, protein deficiency was perceived to be the major nutritional problem of children in developing countries. Later on increasing the energy intake of young children during the complementary feeding period became a priority. Early studies on the pathophysiology of malnutrition are now turned into strategic and practical consequences for the prevention and treatment of severe malnutrition, four of which are presented. (1) Almost half of the deaths worldwide are due to being underweight. Nowadays, well-defined preventive and curative interventions have been identified.

The development of infant formula with optimized protein quality and quantity has been, and still is, the subject of intense investigation. A better understanding of the protein composition of breast milk and infant needs in association with technological breakthroughs in cow’s milk fractionation, has led to the development of infant formulas with a protein content that is closer to that of human milk.

Human milk provides proteins that benefit newborn infants. They not only provide amino acids, but also facilitate the absorption of nutrients, stimulate growth and development of the intestine, modulate immune function, and aid in the digestion of other nutrients. Breastfed infants have a lower prevalence of infections than formulafed infants. Since many women in industrialized countries choose not to breastfeed, and an increasing proportion of women in developing countries are advised not to breastfeed because of the risk of HIV transmission, incorporation of recombinant human milk proteins into infant foods is likely to be beneficial.

I would like first to thank you all for sharing your experiences and exchanging knowledge; we all have benefited from it. We all shared the objectives and the goal that we wish to further the lot of children in the world. To that goal these exciting 3 days have enhanced our ability to carry out our objectives. It is appropriate that we thank the sponsors who have brought us together here, and that is the Nestlé Nutrition Institute, its director, Dr. Ferdinand Haschke and Dr. Denis Barclay who have organized this meeting, and we must also not forget Dr. Philippe Steenhout who conceived this conference and organized it initially before he turned things over to Dr. Barclay and we are grateful for all their efforts. We also express our gratitude to the local organizers, Pierre Schaufelberger; we thank Vipapan Panitantum and Montip Nagsevi and all the other staff of Nestlé Viet Nam for organizing this so splendidly and for feeding us so excellently.

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