Zinc balances in preterm infants.

Zinc balances were studied in three groups of preterm babies. The first group received bank human milk of 25% concentration, the second group bank human milk enriched with 1 g/100 ml of lactalbumin hydrolysate, and the third group an industrial formula in which 40% of the fats were replaced with medium chain triglycerides (MCT). Zn intakes (microgram/kg/day) were, respectively, 796 +/- 136 (group 1), 689 +/- 231 (group 2), and 252 +/- 67 (group 3). In all 3 groups, fecal Zn excretion was very high: range; 6,862-635 micrograms/kg/day (group 1), 3,022-194 micrograms/kg/day (group 2), and 304-27 micrograms/kg/day (group 3), respectively. Zn retentions were mostly negative for groups 1 and 2 (7/8 and 18/23, respectively), and mostly positive (12/14), for group 3. Zn absorption was found to be related to fecal fat (p less than 0.001) in all groups, and in group 1 and 2 to fecal N (p less than 0.001) and Zn intake (p less than 0.02). Positive zinc balances were obtained when fat and nitrogen absorption exceeded 90%. This was achieved at 280 days of postmenstrual age in preterm babies fed bank human milk, but much sooner in preterm babies fed with MCT.