Protein and Energy Intake during Weaning

Abstract
Preprandial plasma amino acid concentrations were measured at 5 and 6 months of age in 30 healthy term infants who were either breast‐fed ad libitum or fed one of two different formulas (1.9 g of protein per 100 ml with a whey: casein ratio of 50:50; 2.9 g of protein per 100 ml with a whey: casein ratio of 20:80) ad libitum, plus the same supplementary food regimen. The mean plasma concentrations of total amino acids and especially total essential amino acids were higher in the formula‐fed infants. Those fed formula also had plasma concentrations of methionine, isoleucine, phenylalanine, leucine, valine, threonine, aspartate, proline, lysine, tyrosine, histidine that exceeded plasma concentrations of breast‐fed infants by 2 or more standard deviations. Concentrations of arginine, glutamic acid, glutamine, ornithine, serine, cystine did not differ and taurine was higher in the breast‐fed infants. The data indicate that formulas in common use today during weaning (4–6 months) provide excessive protein intakes when compared to the breast‐fed control infants. A lowering of protein concentration and a further manipulation of the whey: casein ratio is necessary if plasma amino acid patterns similar to those found in breast‐fed infants is to be achieved with artificial feeding.