Zinc absorption as a function of the dose of zinc sulfate in aqueous solution2

Published:1 December 2004 DOI: 10.1093/ajcn/80.6.1570 PMID: 15585770

Tran Cuong D , Miller Leland V , Krebs Nancy F , Lei Sian , Hambidge K Michael

Abstract

Background

Zinc supplements are used extensively in medicine and research and for public health purposes in the prevention and treatment of zinc deficiency. However, little is known about the efficiency of zinc utilization after different doses.

Objective

The objective was to determine the relation between dose of aqueous zinc and absorbed zinc (AZ) in healthy adults.

Design

Eight healthy adults (3 men and 5 women) aged 33.8 ± 9.8 y (x? ± SD) received 3 pairs of zinc doses (2 and 5, 10 and 15, and 20 and 30 mg) in random order in 3 phases (1 pair per phase). There was a 3-wk washout between phases. Aqueous zinc sulfate labeled with ⁷⁰Zn or ⁶⁸Zn was orally administered in the postabsorptive state on days 1 and 6, respectively; intravenous ⁶⁷Zn was administered 1 h after the first oral zinc dose. Two urine samples were collected daily from days 3 to 15; zinc isotopic ratios were determined by inductively coupled plasma mass spectrometry. Fractional absorption of zinc (FAZ) was determined by dual-isotope-tracer ratio; AZ was calculated by multiplying FAZ by dose.

Results

Mean (±SD) AZ values at doses of 2.2, 5.2, 10.4, 15.2, 20.3, and 30.1 mg ingested Zn were 1.6 ± 0.4, 3.5 ± 1.3, 7.4 ± 1.0, 9.5 ± 2.2, 11.0 ± 4.4, and 11.2 ± 2.1 mg, respectively. A saturable dose-response model, the Hill equation, was selected to model the relation of AZ to ingested zinc. Parameter estimation by nonlinear regression predicted a maximum zinc absorption of 13 mg for larger doses.

Conclusions

Increases in aqueous zinc doses >20 mg result in relatively small and progressively diminishing increases in AZ postabsorptively in healthy adults.