Infant formulas with increased concentrations of α-lactalbumin : Breast milk and breastfed infants: Implications for improving infant formula

Human and bovine milk differ substantially in the ratio of whey to casein protein ( 60:40 in human milk and 20:80 in bovine milk) and in the proportions of specific proteins. Although current infant formulas closely mimic the ratio of total whey to casein in human milk, the concentration of α-lactalbumin (the dominant protein in human milk) is relatively low in formula, whereas (3-lactoglobulin, a protein not found in human milk, is the most dominant whey protein in formula. Because of the differences in the protein profiles of human milk and infant formula, amino acid profiles also differ. To meet all essential amino acid requirements of infants, formula concentrations of protein must be higher than those in human milk. Recently, whey sources with elevated concentrations of α-lactalbumin have become available, which permitted the development of formulas with increased concentrations of this protein and decreased concentrations of β-lactoglobulin. α-Lactalbumin is rich in tryptophan, which is typically the limiting amino acid in formula, and as a result, formulas have been developed with lower protein but higher tryptophan concentrations. This type of formula may offer a number of advantages to the neonate, which include producing plasma tryptophan concentrations equal to those found in breastfed infants and obviating the need for the body to dispose of excess nitrogen loads.