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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 #99878
Title: ADAPTATION IN IRON ABSORPTION: DAILY IRON SUPPLEMENTATION DECREASES ABSORPTION EFFICIENCY OF NONHEME, BUT NOT HEME IRON, FROM FOOD AND SLIGHTLYINCREASES SERUM FERRITIN IN NORMAL VOLUNTEERS

Author
item Roughead, Zamzam
item Hunt, Janet

Submitted to: North Dakota Academy of Science Proceedings
Publication Type: Other
Publication Acceptance Date: 4/15/1999
Publication Date: N/A
Citation: N/A

Interpretive Summary: There are two types of iron in our diet(heme and nonheme). Although we know that the body can adapt the absorption of iron depending on its needs and how much iron is in the food, it is not clear if it handles these two types of iron differently. This iron supplementation study was designed to test for differences in adaptation of heme and nonheme iron absorption and to evaluate if iron stores change with supplementation with iron and if these changes persist once supplementation is stopped. Healthy men and women took either a daily supplement of 50 mg of iron or placebo for 12 weeks. Heme and nonheme Fe absorption from a meal of hamburger, french fries, and milk shake were measured before and after 12 weeks of supplementation. Also, serum ferritin which indicates iron stores, was measured with supplementation and 6 months after supplementation was stopped. We found that with daily iron supplementation, healthy individuals adapted to decrease their nonheme, but not heme iron absorption from food. This indicates that the body handles heme and nonheme iron differently and that there may be more control over the absorption of nonheme iron than heme iron. Also, we found a small increase in iron stores with supplementation and those who had lower iron stores tended to show more increase than those with higher iron stores. This increase in iron stores tended to persist 6 months after iron supplementation was stopped.

Technical Abstract: This study was designed to test for adaptation of heme and nonheme Fe absorption and to evaluate changes in Fe stores, as indicated by serum ferritin, with Fe supplementation and after it was stopped. Healthy men and women were recruited from the community to receive either a daily supplement of 50 mg Fe or placebo for 12 wk. Serum ferritin was monitored an additional 24 wk after supplementation was stopped. Heme and nonheme Fe absorption from a test meal were measured with Fe-59 and Fe-55 radiotracers, before and after 12 wk of supplementation, by using whole body scintillation counting and the ratio of Fe-55/Fe59 in blood after two wk. Daily Fe supplementation for 12 wk resulted in a significant decrease of about 36% in nonheme Fe absorption. A slight reduction in heme Fe absorption with time was not significantly related to Fe supplementation. There was a small, but significant, increase in serum ferritin after 12 wk of Fe supplementation. The increase in serum ferritin at wk 36 of the study, 6 months after supplementation stopped, was so slight as to be detectable only as % change from baseline compared with the placebo group. At all times tested, this change in serum ferritin was positive and higher in the Fe supplemented, as compared to the placebo group in which serum ferritin declined probably because of phlebotomy. In conclusion, with daily Fe supplementation, healthy individuals adapted to decrease their efficiency of nonheme, but not heme, Fe absorption from food. There was a small increase in Fe stores, as indicated by serum ferritin, which tended to persist 6 months after Fe supplementation was stopped.