A 3-MONTH STUDY of LBW INFANTS FED PARTIALLY or EXTENSIVELY HYDROLYSED PRETERM FORMULAS: GROWTH PARAMETERS, INDICES OF PROTEIN METABOLISM, PLASMA AMINO ACID CONCENTRATIONS

Abstract

36 Background: Two previous studies have reported data on plasma amino acid concentrations in infants fed preterm hydrolysed formulas. The use of a high percentage of whey resulted in an increase in plasma threonine and a significant decrease in valine, leucine, tyrosine, phenylalanine and histidine [Acta Pediatr Suppl 405:98-104,1994]. The use of acidic whey reduced hyperthreoninemia and lead to plasma amino acid concentrations close to reference value [JPGN 24:491,1997]. These studies were short-term (analysis were performed at the end of first month) and only one type of hydrolysed preterm formulas was analysed. Aim: The aim of this study was to evaluate the effect of feeding both extensively and partially hydrolysed preterm formulas compared to standard preterm formula and fortified breast milk on growth, indices of protein metabolism (including plasma amino acid concentrations) followed during the first 3 months of life. Methods: Sixty low-birth-weight infants (birth weight 1535±104.2 g), appropriate for gestational age were enrolled into the study. The infants were randomly assigned to receive one of three study formulas: extensively hydrolysed (EH, n=15), partially hydrolysed (PH, n=15) preterm formula, standard preterm formula (SF, n=15) or fortified breast milk (FBM, n=15). The infants were investigated at the ages of 4, 8 and 12 weeks. Physical examination included anthropometric measurements (weight, length, and head circumference). On the day of examination samples of venous blood were obtained following 2-3 hour fast. Serum urea, albumin, prealbumin, transferrin and plasma amino acid concentrations were measured. Overall significance of a group difference was determined by ANOVA for repeated measurements. For the analysis of group differences multiple comparisons procedures (LSD, Duncan) were applied. Results: Weight gain was significantly higher in groups fed PH and SF when compared to the group fed FBM at 8 and 12 weeks. There were no differences with respect to length and head circumference among the groups throughout the study. Serum urea was significantly higher in groups fed EH, PH and SF than in FBM at 12 weeks. Plasma concentrations of albumin, prealbumin and transferrin did not differ throughout the study. Plasma concentrations of total amino acid and total essential amino acid concentrations did not differ. Significant differences were found in plasma concentrations of tyrosine, valine and glutamine. Tyrosine was significantly higher at 4 weeks in groups fed EH and PH than in FBM and at 12 weeks in group PH than in groups fed FBF and EH. Valine was significantly higher in groups fed PH and SF than in group fed FBM at 8 and 12 weeks. Glutamine was significantly higher in groups fed PH and SF than FBM at 8 weeks. Conclusions: In this three-month study of preterm infants fed extensively and partially hydrolysed preterm formula no significant differences were found in growth, indices of protein metabolism and plasma amino acid concentrations as compared with standard preterm formula. Although some significant differences were found in weight gain, urea concentrations and plasma concentrations of some amino acids between preterm infants fed both partially and extensively hydrolysed formulas and those fed fortified human milk, all the parameters were within reference values. These results are indicative of a satisfactory biochemical tolerance of extensively and partially hydrolysed preterm formulas.