NUTRIENT ACCRETION IN PRETERM INFANTS FED FORMULA WITH DIFFERENT PROTEIN - ENERGY RATIOS

Background: Although standard formulas for preterm infants promote int rauterine rates of weight gain, fat deposition in preterm infants fed these formulas has been reported to be considerably higher than that i n the fetus. We hypothesized that a preterm infant formula with a high er protein:energy (P:E) ratio would promote accretion rates of fat, fa t-free mass, and minerals closer to those of the fetus. Methods: As pa rt of a larger study to determine whether accretion rates of fat and f at-free mass closer to those of the fetus can be achieved with a highe r P:E ratio, we present a descriptive analysis of 72-h nutrient balanc e studies performed on a subset (n = 15/30) of the infants randomly as signed to be fed formula with a P:E ratio of either 3.2 g/100 kcal or 2.6 g/100 kcal. Results: Despite the higher intake and net absorption of nitrogen by infants fed the higher P:E formula, there was no statis tically significant difference in net nitrogen retention between group s. There also were no statistically significant differences between gr oups in digestible energy, metabolizable energy, energy expenditure, o r energy storage. Thus, partitioning of stored energy as protein and f at did not differ between groups. The retention of calcium, phosphorus , sodium, potassium, copper, and zinc also did not differ between grou ps, and nitrogen intake did not affect mineral retention. Conclusions: In this study, formula for preterm infants with a P:E ratio of 3.2 g/ 100 kcal vs. 2.6 g/100 kcal provided no apparent benefit in terms of t he proportion of fat to lean tissue accretion as determined from nutri ent balance data. (C) 1997 Lippincott-Raven Publishers.