Iron Bioavailability in Prenatal Multivitamin Supplements with Separated and Combined Iron and Calcium

Objective: To compare iron absorption of a prenatal multivita¬min supplement containing both iron and calcium (HICA) to that of another multivitamin containing a lower iron dose and no calcium (LI).Methods: In a crossover study, serum iron was measured in 12 healthy women administered HICA and LI separately on 2 dif¬ferent occasions. Blood samples were taken at 0, 1, 2, 3, 4, 6, and 8 hours after administration of each supplement.Results: The values of the area under the concentration-time curve (AUC) were not significantly different between LI (79.1 ± 36.0 μM*h) and HICA (91.4 ± 50.4 μM*h) (P = .37). After standardizing the AUC for dose, the relative absorption over the 8-hour time period was significantly higher for LI (2.3 ± 1.0 μM*h/mg) than for HICA (1.5 ± 0.8 μM*h/mg) (P = .021).Conclusion: The absorption of iron from a low-iron-containing supplement was similar to that from a supplement with almost twice the amount of iron, due possibly to the exclu¬sion of calcium in the LI product. Thus, while offering similar amounts of iron, the LI supplement may be better tolerated by women who are sensitive to iron-induced adverse effects.