Serial serum zinc levels in preterm infants during parenteral and enteral feedings.

Weekly serum zinc levels during the neonatal period have been obtained in 17 preterm infants randomly assigned to a prospective feeding study. Nine neonates received a standard regimen of naso-jejunal feedings (group I) and eight matched infants received total parenteral nutrition (group II) for the first 2 wk, followed by enteral intake for the last 2 wk of the study period. No patient received supplemental zinc intake. Base-line serum zinc levels obtained before beginning feedings at 2 days of age were in the normal range and not significantly different, 121 +/- 15 and 135 +/- 8 micrograms/dl in groups I and II, respectively (mean +/- SEM). Serial serum zinc levels decreased progressively in both groups during the 4-wk study period, reaching a low of 80 +/- 7 micrograms/dl in group I and 85 +/- 10 micrograms/dl in group II. The progressive decline in serum zinc levels is postulated to be indicative of tissue depletion of zinc. Our data suggest that preterm infants fed either by short-term total parenteral nutrition or by transpyloric enteral feedings are at risk for marginal zinc deficiency states.