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Biol Trace Elem Res. 2007 Summer;117(1-3):7-14.

Zinc inhibits nonheme iron bioavailability in humans.

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Institute of Nutrition and Food Technology (INTA), University of Chile, Macul 5540, Casilla, Santiago, 138-11, Chile.


There is increasing concern about potential negative interactions in combined iron and zinc supplementation. The aim of the present study was to determine the dose-response effect of zinc, given as a solution, on iron bioavailability. Twenty-two healthy adult women were selected to participate in the study. Iron, with or without zinc was given as an aqueous solution on d 1,2,14, and 15 of the study. Iron bioavailability was measured on the basis of erythrocyte incorporation of 55Fe or 59Fe 14 d after administration. Subjects received 0.5 mg of iron together with graded zinc concentrations (0-11.71 mg). No significant effect of zinc on iron absorption was found at Zn:Fe molar ratios up to 2:1. At 5:1,10:1, and 20:1 molar ratios, a dose-dependent inhibitory effect on iron absorption was observed (28-40% of iron absorption inhibition; one-way repeated-measures ANOVA, F=4.48, p=0.02). In conclusion, zinc administration combined with iron in an aqueous solution leads to the inhibition of iron bioavailability, which occurs in a dose-dependent way. This negative interaction should be considered for supplementation programs with both microminerals.

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