Submitted to: International Society For Trace Elements Research In Humans
Publication Type: Abstract Only
Publication Acceptance Date: 9/26/1998
Publication Date: N/A
Technical Abstract: Iron absorption was measured in 31 healthy U.S. men at days 1-2 and 71-72 of weighed diets with either high (H) or low (L) iron bioavailability (differing in content of meat, ascorbic acid, whole grains, legumes, and tea). The H and L diets contained, respectively 14.6 and 15.3 mg/d nonheme iron and 1.8 and 0.1 mg/d heme iron. Men >32 y (mean 44, range 32 to 56) were studied because of their relatively stable serum ferritin (mean 102, range 17 to 308 ug/L). Heme and nonheme iron absorption from the entire 2-d menu were measured by using Fe-55 and Fe-59, whole body scintillation counting, and the ratio of isotopes in blood after 2 wk. Serum ferritin was insensitive to diet, but significantly decreased ~20% on both diets, with procedural phlebotomy. Fecal ferritin decreased significantly on the L diet, to less than 15% of that on the H diet. Absorption accounted for 95% (R2) of the variance in blood Fe-59 at 2 wk. Erythrocyte incorporation of absorbed iron was 64 (37 to 94)%, associated directly with red cell distribution width and inversely with serum ferritin. Total iron absorption decreased with the H diet from 0.96 to 0.69 mg/d (p<0.05) and increased with the L diet from 0.12 to 0.17 mg/d (p<0.05) in 10 wk. This was characterized by adaptation in nonheme, but not heme iron absorption. U.S. men have not exhausted their ability to reduce iron absorption, but adapt to absorb less than the commonly assumed 1 mg/d.