Much less is known about the postabsorptive interactions between these nutrients ( 4). When both nutrients are ingested simultaneously in aqueous solutions at levels commonly used in supplements, there is evidence that an excess of iron inhibits zinc absorption ( 1, 2) and that excess zinc inhibits iron uptake ( 3). Zinc and iron interact competitively during intestinal absorption. Zinc, iron, absorption, supplementation, humans However, use of a modest zinc supplement improves zinc indices, but also appears to induce a cellular iron deficiency and, possibly, further reduce iron status. Our results indicate that the use of iron supplements in women with marginal iron status improves iron indices with no effect on zinc status.

Iron absorption (%) from the test meal increased ( P < 0.01), whereas zinc absorption (%) decreased ( P < 0.01) compared with baseline in the Zn-supplemented women. Plasma and urinary zinc also increased ( P < 0.01). In the zinc-supplemented group, plasma ferritin and the percentage of transferrin saturation decreased ( P < 0.05), whereas the plasma transferrin receptor and erythrocyte zinc protoprophyrin levels increased ( P < 0.05). In the iron-supplemented group, blood hemoglobin, plasma ferritin and the percentage of transferrin saturation increased ( P < 0.01). Radioiron and stable isotopes of zinc were used to measure iron and zinc absorption from a test meal. Iron and zinc biochemical indices and intestinal absorption were measured on d 1 and 56. The women were divided in two groups (zinc-supplemented, n = 11 iron-supplemented, n = 12). Young adult women (ages 20–28 y), nonanemic but with low iron stores (plasma ferritin< 20 μg/L), participated in the 70-d study. The effect of zinc supplementation (22 mg Zn/d as zinc gluconate) or of iron supplementation (100 mg Fe/d as ferrous sulfate) for 6 wk on iron and zinc metabolism and absorption was evaluated in young women with low iron reserves. Understanding these interactions is important to determine when supplementation with iron or zinc is proposed. Zinc and iron compete during intestinal absorption, but postabsorptive interactions between these nutrients are less clear.

Blood and iron new west