Dietary protein source and plasma lipid profiles of infants.

Total cholesterol and triglyceride concentrations were measured in plasma samples taken at 4 and 8 weeks of age from 40 full-term infants who had been fed either human milk or one of three formulas containing casein-to-whey ratios of 82:18, 66:34, or 50:50 to investigate whether dietary protein influenced the development of plasma lipid profiles. Infants fed the formula with the casein-to-whey ratio of 82:18 had significantly higher plasma cholesterol levels at both 4 and 8 weeks of age compared with other groups of infants (P less than .05). Infants fed the high-casein formula also showed an increase in plasma cholesterol levels with time (P less than .001). Plasma triglyceride concentrations decreased as concentration of casein decreased (P less than .05) among the formula-fed groups and increased with time. Infants fed human milk had plasma triglyceride concentrations similar to those infants who had been fed the 82:18 formula at 4 weeks of age; however, triglyceride concentrations eventually fell and were similar to those concentrations in infants who had been fed the 50:50 formula at 8 weeks of age. Results indicate that constituent lipids of human milk or formulas were not determining factors for changes observed in plasma cholesterol levels and triglyceride concentrations among groups. Since formulas differed only in proteins and their constituent amino acids, further investigation of the impact of dietary protein (amino acids) on development of blood lipid profiles in infants is warranted.