Current dietary zinc intake has a greater effect on fractional zinc absorption than does longer term zinc consumption in healthy adult men

Abstract

Background: No studies have examined the independent effects of current and longer-term dietary zinc intakes on zinc absorption. Objective: We determined the effects of current compared with longer-term zinc intake on fractional zinc absorption (FZA). Design:Westudied 9 men whose usual zinc intakes were>11 mg/d. FZA was measured at baseline, depletion (0.6 mg Zn/d for 1 wk and 4 mg Zn/d for 5 wk), and repletion (11 mg Zn/d for 4 wk with 20 mg supplemental Zn/d for first 7 d). During 2 successive days after each dietary period, subjects consumed either adequate-zinc meals (11 mg Zn/d) with a zinc stable isotope tracer for 1 d, followed by low-zinc meals (4 mg Zn/d) with zinc tracer, or vice versa. Five days after oral dosing, a zinc tracer was infused intravenously. FZA was measured with the use of a modified double isotope tracer ratio method with urine samples collected on days 5-7 and 10-12 of absorption studies. Results: Plasma and urinary zinc did not vary by dietary period. Mean FZA was greater from low-zinc meals than from adequate-zinc meals (60.9% ± 13.8% compared with 36.1% ± 8.9%; P < 0.0001), whereas mean total absorbed zinc was greater from adequate-zinc meals than from low-zinc meals (3.60 ± 0.91 compared with 2.48 ± 0.56; P < 0.0001), regardless of the longer-term dietary period. Conclusions: FZA was inversely related to current zinc intake, but there was no detectable effect of longer-term dietary zinc. If longer-term zinc intake does modify FZA, such changes are smaller than those caused by current zinc intake, or they occur only after more severe zinc depletion. © 2008 American Society for Nutrition.