Submitted to: Journal of Federation of American Societies for Experimental Biology
Publication Type: Abstract Only
Publication Acceptance Date: 12/2/2002
Publication Date: 3/14/2003
Citation: Roughead, Z.K., Zito, C.A., Hunt, J.R. 2003. Dietary calcium (ca) inhibits the intestinal uptake, not transfer, of heme iron (fe) and reduces total fe retention from a typical western meal [abstract]. Journal of Federation of American Societies for Experimental Biology. 17(5):A1086.
Technical Abstract: The inhibitory effects of Ca on the initial mucosal uptake, serosal transfer, and retention of heme and nonheme Fe were tested by combining gastrointestinal lavage and whole body counting methodology. Healthy volunteers (n=12, 22-49 y; ferritin 13-220 µg/L) ate hamburger test meals (5 mg Fe, 0.7 mg as heme Fe) labeled with both nonheme Fe-59 and heme Fe-55, with and without a Ca supplement (448 mg Ca as citrate), 6 wk apart, in a randomized crossover design. To determine initial uptake, the gut was purged with an oral isosmotic/isotonic polyethylene glycol solution 8 h after each meal, followed by whole body counting and analyses of the radiotracers in the lavage excreta. Compared to no added Ca, Ca reduced the initial mucosal uptake (49 vs 40% of dose, p<0.02), but not the fractional serosal transfer of heme Fe (0.48 vs 0.44 of initial uptake, p>0.1), resulting in retention of 22 vs 16% of dose, respectively (p<0.01). The same tendency was observed for nonheme Fe, with initial mucosal uptake of 13 vs 10% of dose (p>0.1), fractional serosal transfer 0.70 vs 0.72 of initial uptake (p>0.1), and retention of 8 vs 6% of dose (p<0.07), respectively. As a result, 0.55 and 0.40 mg total Fe (p<0.01) (0.36 mg and 0.27 mg as nonheme, p<0.07) were retained, respectively. Thus, supplemental Ca reduced total Fe retention from this typical Western meal by 25%. Ca reduced heme Fe retention during initial mucosal uptake, rather than serosal transfer.