Site of Iron Absorption in Man

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Abstract
This study was done to test the assumption that the duodenum is the site of most efficient iron absorption in man. In 8 normal and 9 iron deficient subjects a preselected intestinal site was incubated. On alternate days for 6 days either59Fe or55Fe was given with 5 mg. of carrier iron, one isotope by mouth, the other by tube. Two weeks later red cells were assayed for each isotope and the ratio of the isotope given orally to the isotope given by tube was determined. This ratio reflects the effect of bypassing the selected gastrointestinal segment. Results showed that iron is absorbed along the entire small intestine. When the doses of iron were put into proximal jejunum of normal subjects results varied but absorption decreased as much as 50% compared to absorption following the oral dose. In normal man the small intestine proximal to the mid‐jejunum may be capable of more efficient iron absorption than the distal portion. In iron deficiency enhanced absorption extends distally to about the mid‐jejunum.