Calcium bioavailability and iron-calcium interaction in orange juice.

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Abstract
We have determined the effects of orange juice on calcium bioavailability from CCM (a combination of CaCO3, citric acid, malic acid, 5:1:1, mol/mol/mol) and iron-calcium interaction by using whole body isotope retention techniques in rats. The mean calcium retention values from CCM were 42.8% from orange juice and 33.0% from water, a control. Orange juice significantly (p less than 0.05) improved calcium bioavailability. This enhancement of calcium absorption is independent of orange juice's pH and citric acid. Iron absorption from orange juice with CCM (36.7%) was also significantly higher than that from control (water) plus CCM (12.3%). Ascorbic acid at levels naturally present in orange juice failed to improve iron retention (12.3% vs 12.5%) from water plus CCM. In contrast, citric acid (at orange juice level) significantly (p less than 0.05) promoted iron absorption in the presence of CCM (8.0% vs 23.7%). The benefit of citric acid on iron-calcium interaction is enhanced by ascorbic acid. In the presence of both citric acid and ascorbic acid, at orange juice levels, iron absorption from water plus CCM (37.6%) was comparable to that from water without CCM (34.5%). These results show orange juice can deliver bioavailable calcium from CCM with minimal inhibition of iron absorption. Citric acid and ascorbic acid are likely the major orange juice components that contribute to the alleviation of iron absorption inhibition by CCM.