Submitted to: Journal of Federation of American Societies for Experimental Biology
Publication Type: Abstract Only
Publication Acceptance Date: December 10, 1999
Publication Date: March 15, 2000
Citation: Roughead, Z.K., Zito, C.A., Hunt, J.R. 2000. Human absorption of nonheme iron is primarily determined by initial mucosal uptake. The Federation of American Societies for Experimental Biology Journal. 14:A297. Technical Abstract: Gastrointestinal lavage and whole body scintillation counting of an orally administered iron tracer were applied in a new method to distinguish between the initial uptake and mucosal transfer steps of iron absorption, as well as the blood incorporation of the absorbed iron. Healthy volunteers (n=17, age 23-52 y; serum ferritin 11-191 ug/L) consumed a hamburger test meal containing Fe-59 radiotracer. The gut was cleansed 8 h later with an orally administered isosmotic/isotonic solution containing polyethylene glycol. The initial uptake of nonheme iron was determined by comparing the amount of Fe-59 in the body after the lavage procedure to the initial dose, both measured by whole body scintillation counting. Similarly, nonheme iron absorption was measured 2 wk after the test meal. Mucosal transfer was calculated as absorption divided by initial uptake, both expressed as percent of initial dose. Data are expressed as geometric means (-SD, +SD) except for mucosal transfer data which are arithmetic means +/- SD. Of the administered dose of iron, about 10.6% (6.4-17.5) was initially taken-up by the mucosal cell and 6.6% (3.0-14.4) was absorbed into the body. About 2/3 (67% +/- 21) of the iron initially taken-up by the mucosa was transferred to the body. Approximately 71% (62-83) of the absorbed iron was incorporated into blood after 2 wk. Serum ferritin correlated inversely (p<0.05) with the initial uptake (R**2 =0.40), absorption (R**2 =0.30) and blood incorporation (R**2 =0.63) of iron, but not its mucosal transfer. The inclusion of about 170 mg of calcium (as cheese) to the meal did not change any of these measurements. The results indicate that the initial uptake, not the mucosal transfer, of iron was the primary determinant of nonheme iron absorption in humans.