title: Effect of low zinc intake on absorption and excretion of zinc by infants studied with 70Zn as extrinsic tag.
abstract: The effect of low dietary intake of zinc was studied in six normal infants with the use of 70Zn as an extrinsic tag. Of the two study formulas, one provided a zinc intake similar to that of customary infant formulas ("high" intake), whereas the other provided a "low" zinc intake. Two zinc absorption studies were performed with each formula (sequence: high-low-low-high). Extrinsically labeled formula was fed for 24 h and excreta were collected for 72 h. Zinc isotope ratios were determined by inductively coupled plasma mass spectrometry (ICP/MS). When zinc intake was high, net zinc absorption was 9.1 +/- 8.7% (mean +/- SD) of intake and net zinc retention was 74 +/- 91 micrograms/(kg.d). True zinc (70Zn) absorption was 16.8 +/- 5.8% of intake and fecal excretion of endogenous zinc was 78 +/- 56 micrograms/(kg.d). When zinc intake was low, net absorption of zinc increased significantly (P less than 0.001) to 26.0 +/- 13.0% of intake, but net retention was not significantly different at 42 +/- 33 micrograms/(kg.d). True absorption of zinc also increased significantly (P less than 0.001) to 41.1 +/- 7.8% of intake, whereas fecal endogenous zinc decreased (P less than 0.05) to 34 +/- 16 micrograms/(kg.d) during low zinc intake. Thus, infants maintain zinc balance in the face of low zinc intake through increased efficiency of absorption and decreased excretion of endogenous zinc.
authors.affiliation: Dept. of Pediatrics, University of Iowa, Iowa City 52242.
authors.forename: E E
authors.initials: EE
authors.lastname: Ziegler
authors.forename: R E
authors.initials: RE
authors.lastname: Serfass
authors.forename: S E
authors.initials: SE
authors.lastname: Nelson
authors.forename: R
authors.initials: R
authors.lastname: Figueroa-Colón
authors.forename: B B
authors.initials: BB
authors.lastname: Edwards
authors.forename: R S
authors.initials: RS
authors.lastname: Houk
authors.forename: J J
authors.initials: JJ
authors.lastname: Thompson
mesh_terms: D000222:Adaptation, Physiological; D000704:Analysis of Variance; D005243:Feces / Q000032:analysis; D005260:Female; D006801:Humans; D007223:Infant; D007227:Infant Nutritional Physiological Phenomena; D007408:Intestinal Absorption; D008297:Male; D015032:Zinc / Q000008:administration & dosage / Q000493:pharmacokinetics* / Q000652:urine; D015033:Zinc Isotopes
chemical_list: D015033:Zinc Isotopes; D015032:Zinc