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ARS Home » Plains Area » Grand Forks, North Dakota » Grand Forks Human Nutrition Research Center » Healthy Body Weight Research » Research » Publications at this Location » Publication #87268
Title: IRON ABSORPTION ADAPTS TO DIETARY IRON BIOAVAILABILITY

Author
item Hunt, Janet
item Zito, Carol

Submitted to: Federation of American Societies for Experimental Biology Conference
Publication Type: Abstract Only
Publication Acceptance Date: 4/17/1998
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Human adaptation to dietary Fe bioavailability was evaluated by measuring iron (Fe) absorption in men before and after consuming diets high (H) or low (L) in Fe bioavailability. Healthy men were randomly assigned to consume H or L weighed diets for 12 weeks. The diets differed in content of meat, ascorbic acid, whole grain products, and tea. The H and L diets contained, respectively, 16.2 and 16.6 mg nonheme Fe and 2.0 and 0.1 mg heme Fe daily per 3500 kcal. Heme and nonheme Fe absorption from the entire 2-d cycle menu were measured with Fe-55 and Fe-59 radiotracers on days 1-2 and 71-72, by using whole body scintillation counting and the ratio of Fe-55/Fe-59 in blood after 2 wk. Preliminary data (geometric means) from 19 men are presented. Initial serum ferritin values did not differ between the diet groups (H 122 and L 96 ug/L, NS) and a significant decrease in both groups of about 25 ug/L between wk 0 and 12 was not associated with diet assignment. Despite this decrease, nonheme Fe absorption decreased by 40% from the H diet after 10 wk. Nonheme Fe absorption increased 30% from the L diet (diet significantly affected the absorption ratio at 10 / 0 wk, p<0.01). This partial adaptation changed the relative nonheme Fe bioavailability between the two diets from 5-fold (H 3.7 vs. L 0.7%, p<0.01 at 0 wk) to just over 2-fold (2.2 vs. 0.9%, p<0.01 at 10 wk). There was no adaptation in heme Fe absorption. In conclusion, biological adaptation reduces the influence of dietary Fe bioavailability with time. Although a cross-sectional inverse relationship between serum ferritin and nonheme Fe absorption is well established, these results demonstrate, for the first time, a longitudinal adaptation in Fe absorption, apparently independent of serum ferritin.