Protein requirements during the first year of life.

The composition of human milk provides the model for estimated total protein and essential amino acid requirements during infancy. However, both the total protein content and the concentrations of individual proteins in human milk change throughout the first year of lactation. Recent reassessments of estimated requirements have resulted in lower total protein recommendations and have emphasized the provision of alpha-amino nitrogen because most nonprotein nitrogen is not used for maintenance or tissue deposition. In clinical studies, formulas containing various whey-to-casein ratios and having total protein concentrations in the range of 13-15 g/L were shown to promote adequate growth and to result in biochemical measures of protein nutritional status similar to those in breastfed infants. In the second half of infancy, human milk can provide most of the protein needed, provided a modest protein supply is obtained from weaning foods. In special situations in which greater protein intakes are desired, special preparations of protein might be needed.