Article

Major variables of zinc homeostasis in Chinese toddlers. Am J Clin Nutr

Department of Child and Adolescent Health, Xin-Hua Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China.
American Journal of Clinical Nutrition (Impact Factor: 6.92). 09/2006; 84(2):389-94.
Source: PubMed

ABSTRACT Measurement of the major variables of zinc homeostasis is an essential prerequisite for estimating human zinc requirements, which currently require a factorial approach. The data required for this approach have not been available for toddlers, whose requirements have been estimated by extrapolation from other age groups.
The objective of the study was to measure key variables of zinc homeostasis in rural and small-town Chinese toddlers.
Zinc stable-isotope tracers were administered intravenously and orally with all meals for 1 d to 43 toddlers. Subsequent metabolic collections in the homes included duplicate diets, quantitative fecal collections, and spot urine sampling. Fractional absorption of zinc (FAZ) was measured by a dual-isotope tracer ratio technique, and endogenous fecal zinc (EFZ) was measured by an isotope dilution technique.
No group or sex differences were found. Therefore, results were combined for 43 toddlers aged 19-25 mo whose major food staple was white rice. Selected results (x+/- SD) were 1.86 +/- 0.55 mg total dietary Zn/d; 0.35 +/- 0.12 FAZ; 0.63 +/- 0.24 mg total absorbed Zn/d; 0.67 +/- 0.23 mg EFZ/d; and 65.0 +/- 8.3 microg plasma Zn/dL. The molar ratio of dietary phytate to zinc was 2.7:1.
The mean intake and absorption of zinc in this population are low in comparison with estimated average dietary and physiologic requirements for zinc, and plasma zinc values are consistent with zinc deficiency. Intestinal losses of endogenous zinc exceed previous estimates for toddlers, and only modest evidence exists of conservation in response to low zinc intake and absorption.

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    • "Simulations of zinc absorption by children – Similar attempts to estimate the effect of different levels of zinc fortification on TAZ among young children are complicated by the fact that specific prediction equations are not yet available for children. The adult model (Miller, 2007) provides a good fit for data from children aged 2 years consuming a low phytate diet (Sheng, 2006) after adjustment for difference in the length of their small intestine compared with adults (Hambidge, unpublished); but there are no data available to model for the effect of phytate in younger children, and the 'gut length adjustment' is very crude. Thus, it is still not known whether it is appropriate to apply the same prediction equation derived from absorption studies conducted among adults to estimate zinc absorption by children. "
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