Effects of feeding ultrahigh-temperature (UHT)-treated infant formula with different protein concentrations or powdered formula, as compared with breast-feeding, on plasma amino acids, hematology, and trace element status

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Abstract
The appropriate amount of protein to use in infant formula is still under discussion. We found earlier that protein digestibility is higher from ultrahigh-temperature (UHT)-treated formula than from conventionally heat-treated formula. In this study, we evaluated the nutritional, hematologic, and biochemical effects of feeding infants whey-predominant UHT-treated formula with 13 (UHT-13) or 15 (UHT-15) g protein/L as compared with a conventional, powdered, whey-predominant formula (PF) with 13 g protein/L from 6 wk to 6 mo of age. Breast-fed infants served as control subjects. Growth was assessed at monthly intervals and venous blood samples were drawn at entry into the study and at 6 mo of age. At 6 mo, there were no significant differences in weight gain or linear growth, or hemoglobin, serum ferritin, zinc, or copper concentrations among the groups. Blood urea nitrogen concentrations were lowest for breast-fed infants; among the formula-fed groups the UHT-13 group had the lowest values. All formula-fed groups had higher plasma threonine concentrations than breast-fed infants. Infants fed the UHT-13 formula had threonine values closest to those of breast-fed infants. Concentrations of branched-chain amino acids were similar in breast-fed infants and those fed UHT-13 formula, whereas the other groups had higher values. Plasma tryptophan concentrations were significantly higher in the UHT-treated formula groups than in the other groups. Thus, infants fed UHT-13 formula had metabolic measures similar to those of breast-fed infants, possibly because of high protein digestibility, or a difference in the protein source used. Iron, zinc, and copper status was satisfactory in all groups. Selenium status, as indicated by serum glutathione peroxidase activity, varied with dietary selenium intake.