Plasma amino acid concentrations, indexes of protein metabolism and growth in healthy, full-term infants fed partially hydrolyzed infant formula

Abstract

Background: It has been reported that feeding extensively hydrolyzed infant formula influenced the availability of arginine, glycine, histidine, lysine and threonine in full-term infants investigated during the first 2 months of life. In the present study, the nutritional effects of feeding partially hydrolyzed formula (PHF) were investigated.

Methods: Term infants fed conventional formula (F; n = 11) or PHF (n = 11) were investigated at the ages of 5, 30, 60, 90, and 120 days. Anthropometric data were obtained, and plasma amino acid concentrations and biochemical indices of protein metabolism were measured.

Results: Plasma concentrations (in micromoles per liter) of lysine on day 90: 117 (21) versus 143 (24); of threonine on day 30: 140 (53) versus 263 (87); of ornithine on day 90: 56 (21) versus 78 (29); and of tyrosine on day 30: 52 (17) versus 77 (20), on day 60: 56 (14) versus 87 (19) and on day 90: 46 (9) versus 81 (17) were significantly lower in infants receiving PHF than in those fed F. Values are median (range from 1st to 3rd quartile), PHF versus F; p < 0.05. At day 120, infants fed PHF showed significantly lower serum albumin concentrations than did infants receiving F (43.3 +/- 3.4 versus 48.9 +/- 3.5, g/l; mean +/- SD; p < 0.05). Serum creatinine, urea nitrogen, uric acid and total protein concentrations and gain in weight, length, and head circumference did not differ throughout the study.

Conclusions: In this study, feeding PHF did not affect the majority of plasma amino acid concentrations, some indices of protein metabolism, and basic parameters of growth in full-term infants. However, plasma concentrations of lysine, threonine, tyrosine, ornithine, and albumin were, on at least one occasion, significantly lower in infants fed PHF than in those receiving F.