INDICES OF PROTEIN METABOLISM IN TERM INFANTS FED HUMAN MILK, WHEY PREDOMINANT FORMULA, OR COW MILK FORMULA

Abstract

Infants (n=37) received either human milk (HM), whey predominant formula (WF), or cow milk formula (CF) as the sole nutritional source for 2 mos. At age 2, 4, and 8 wks, 2 hr fasting blood was analyzed for plasma amino acids (AA) and serum urea nitrogen (SUN). From 3-day dietary records and direct analyses of milks, intakes of AA and total nitrogen (TN) were calculated. Compared to HM feeding, elevated plasma valine (VAL), phenylalanine (PHE), methionine (MET), and SUN concentrations were observed with WF and CF feeding. Feeding WF resulted in elevations of 4 additional AA [threonine (THR), lysine, leucine (LEU), and isoleucine (ILE)]. Intakes of TN were positively correlated with plasma concentrations of VAL, LEU, ILE, tyrosine (TYR), histidine (HIS), and SUN (r=0.38-0.64, p<0.05-0.001), and negatively correlated with plasma arginine concentrations (r=-0.41, p<0.05). Intakes of the essential amino acids THR, VAL, LEU, ILE, PHE, HIS, TYR, and MET were correlated with their respective plasma concentrations (r=0.38-0.74, p<0.05-0.001). Data indicate that feeding WF does not result in indices of protein metabolism more similar to those obtained with HM feeding than does feeding CF, and that such indices will not be achieved unless TN content of formula is reduced, regardless of relative whey to casein ratios. (Supported in part by the Illinois Agricultural Experiment Station and Ross Laboratories.)