Major variables of zinc homeostasis in Chinese toddlers.
BACKGROUND
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.


OBJECTIVE
The objective of the study was to measure key variables of zinc homeostasis in rural and small-town Chinese toddlers.


METHODS
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.


RESULTS
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.


CONCLUSIONS
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.
Sheng
Xiao-Yang
XY
Department of Child and Adolescent Health, Xin-Hua Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China. xiaoyang.sheng@uchsc.edu
Hambidge
K Michael
KM
Zhu
Xi-Xiang
XX
Ni
Jun-Xue
JX
Bailey
Karl B
KB
Gibson
Rosalind S
RS
Krebs
Nancy F
NF
D002675:Child, Preschool; D002681:China; D004032:Diet; D005243:Feces / Q000737:chemistry; D005260:Female; D006706:Homeostasis / Q000502:physiology; D006801:Humans; D007201:Indicator Dilution Techniques; D007223:Infant; D007262:Infusions, Intravenous; D007408:Intestinal Absorption; D008297:Male; D018673:Nutrition Policy; D009751:Nutritional Requirements; D009752:Nutritional Status; D010833:Phytic Acid / Q000008:administration & dosage; D016482:Urinalysis; D015032:Zinc / Q000008:administration & dosage / Q000172:deficiency* / Q000378:metabolism* / Q000493:pharmacokinetics; D015033:Zinc Isotopes
D015033:Zinc Isotopes; D010833:Phytic Acid; D015032:Zinc