Effects of alpha-lactalbumin-enriched formula containing different concentrations of glycomacropeptide on infant nutrition.

Background: Formula-fed infants have growth and plasma amino acid patterns different from those of breastfed infants.

Objective: alpha-Lactalbumin is a major protein in human milk, and the addition of bovine alpha-lactalbumin to infant formula has been proposed to modify the plasma amino acid pattern of the recipient infant, possibly allowing a reduction in the protein content of the formula, which may affect growth.

Design: We compared breastfed infants and infants fed standard formula or alpha-lactalbumin-enriched formulas (25% of protein) with glycomacropeptide accounting for 15% or 10% of the protein. The protein content of each formula was 13.1 g/L. Ninety-six infants aged 6 +/- 2 wk were recruited. Anthropometric measures were recorded, and interviews were conducted at enrollment and monthly until 6 mo of age. Blood samples were collected at enrollment and at 4 and 6 mo.

Results: Formula intake did not differ between groups, and weight gain in the alpha-lactalbumin-enriched formula groups were similar to that of the breastfed infants. The standard formula group gained significantly more weight than did the breastfed infants. All formula-fed infants had significantly higher plasma concentrations of most essential amino acids at 4 and 6 mo than did the breastfed infants, and serum urea nitrogen was also higher in the formula-fed infants. Insulin and leptin concentrations did not differ between groups.

Conclusions: Compared with standard formula-fed infants, infants fed formula with a modified protein composition had growth patterns more similar to those of breastfed infants. All formula-fed groups had plasma amino acid concentrations similar to or higher than those of breastfed infants. This indicates that the protein content of alpha-lactalbumin-enriched formula can be further reduced, which should be evaluated.