Initial uptake and absorption of nonheme iron and absorption of heme iron in humans are unaffected by the addition of calcium as cheese to a meal with high iron bioavailability.
BACKGROUND
Quantitative data on the mucosal uptake and serosal transfer of nonheme-iron absorption in humans and the effects of calcium on these components are limited.


OBJECTIVE
Our objective was to measure the initial mucosal uptake and the subsequent serosal transfer of nonheme iron and to determine the effects of adding calcium to a meal on both heme- and nonheme-iron retention.


METHODS
Whole-gut lavage and whole-body scintillation counting methods were applied to determine the 8-h uptake of nonheme iron and the 2-wk retention (absorption) of heme and nonheme iron in healthy adults (n = 17) after the consumption of meals of radiolabeled food.


RESULTS
The initial uptake and absorption of nonheme iron were 11% and 7%, respectively, and the absorption of heme iron was 15%. Two-thirds of the nonheme iron taken up by the mucosa within 8 h was retained by the body after 2 wk (serosal transfer index: 0.63). Serum ferritin correlated inversely with the initial uptake and absorption of nonheme iron, but not with the nonheme serosal transfer index or the absorption of heme iron. Adding calcium (127 mg in cheese) to the meal did not affect absorption.


CONCLUSIONS
On the basis of its association with serum ferritin, the initial mucosal uptake was the primary control point for nonheme-iron absorption. An apparent reduction in heme-iron absorption associated with the lavage procedure suggested that uptake of heme iron may take longer and proceed further through the intestine than that of nonheme iron. The absorption of both forms of iron was unaffected by the addition of cheese to this meal with high iron bioavailability.
Roughead
Zamzam K Fariba
ZK
US Department of Agriculture, Agricultural Research Service, Grand Forks Human Nutrition Research Center, Grand Forks, ND 58202-9034, USA. froughea@gfhnrc.ars.usda.gov
Zito
Carol A
CA
Hunt
Janet R
JR
D000284:Administration, Oral; D000328:Adult; D001682:Biological Availability; D015992:Body Mass Index; D002118:Calcium / Q000008:administration & dosage / Q000494:pharmacology; D004912:Erythrocytes / Q000378:metabolism*; D005260:Female; D005293:Ferritins / Q000097:blood; D005751:Gastric Lavage; D006801:Humans; D007408:Intestinal Absorption / Q000187:drug effects; D007413:Intestinal Mucosa / Q000000981:diagnostic imaging / Q000378:metabolism; D007501:Iron / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics*; D008297:Male; D008875:Middle Aged; D011877:Radionuclide Imaging
D005293:Ferritins; D007501:Iron; D002118:Calcium