Effect of various calcium salts on non-heme iron bioavailability in fasted women of childbearing age

Introduction Micronutrient deficiencies are one of the most important public health issues worldwide and iron (Fe) deficiency anemia is the most prevalent micronutrient deficiency. Iron deficiency often coexists with calcium deficiency and iron and calcium supplementation often overlap. This has led to investigations into the interaction between these two minerals, and whether calcium may inhibit iron absorption in the gut. Objective To determine the effect of various calcium salts on non-heme iron bioavailability in fasted women of childbearing age. Methods A randomized and single blinded trial was conducted on 27 women of childbearing age (35–45 years old) divided into 2 groups (n1 = 13 and n2 = 14, respectively). On four different days, after an overnight fast, they received 5 mg of Fe as FeSO4 (labeled with 55Fe or 59Fe) with 800 mg of elemental calcium in the form of either calcium chloride, calcium gluconate, calcium citrate, calcium carbonate, calcium lactate, calcium sulfate or calcium phosphate. Calcium chloride was used as the control salt in both groups. Iron was labeled with the radioisotopes 59Fe or 55Fe, and the absorption of iron was measured by erythrocyte incorporation of radioactive Fe Results 800 mg of elemental calcium as calcium citrate produced a significant decrease in non-heme iron bioavailability (repeated measures ANOVA, F = 3.79, p = 0.018). Conclusion Of the various calcium salts tested, calcium citrate was the only salt that decreased non-heme iron bioavailability relative to the calcium chloride control when taken on an empty stomach. These results suggest that inhibition of non-heme iron absorption in fasted individuals is dependent upon the calcium salt in question and not solely dependent on the presence of calcium.