Exchangeable zinc pool size at birth is smaller in small-for-gestational-age than in appropriate-for-gestational-age preterm infants

Exchangeable zinc pool size at birth is smaller in small-for-gestational-age than in appropriate-for-gestational-age preterm infants1,2,3 Nancy F Krebs, Jamie L Westcott, Donna J Rodden, Katharine W Ferguson, Leland V Miller and K Michael Hambidge 1 From the Section of Nutrition, Department of Pediatrics (NFK, JLW, KWF, LVM, and KMH), and the Pediatric General Clinical Research Center (DJR), University of Colorado School of Medicine, Denver, CO Background: Small-for-gestational-age (SGA) infants are susceptible to postnatal zinc deficiency, but whether this susceptibility is due to intrauterine factors or to high postnatal growth requirements is unknown. Objective: We hypothesized that the size of the exchangeable zinc pool (EZP), which reflects metabolically available zinc, would be smaller in SGA than in appropriate-for-gestational-age (AGA) infants born prematurely. Design: Intravenous 70Zn (45 \ub5g/kg) was administered to 10 SGA infants (8 boys) with a mean (\ub1SD) gestational age of 33.3 \ub1 1.8 wk and to 11 AGA infants (8 boys) with a mean (\ub1SD) gestational age of 32.4 \ub1 1.2 wk within 24 h of birth. The EZP was determined from isotope enrichment in spot urine collections on days 3\u967. Results: The mean birth weight of the SGA infants was 1.30 \ub1 0.2 kg and of the AGA infants was 1.84 \ub1 0.3 kg (P =3D 0.0001). The EZP size was significantly smaller in the SGA than in the AGA infants on an absolute basis (13.3 \ub1 2.8 and 25.2 \ub1 8.1 mg; P =3D 0.0002) and relative to body weight (10.3 \ub1 2.5 and 13.9 \ub1 4.5 mg/kg; P =3D 0.02). The difference remained significant after adjustment for gestational age and birth weight. Conclusion: These data provide evidence for differential zinc status at birth between SGA and AGA infants born prematurely at similar stages of gestation and offer at least a partial explanation for the reported benefits of postnatal zinc supplementation