Iron in prenatal multivitamin/multimineral supplements. Bioavailability

To determine the effect of the differences in the content of essential and nonessential ingredients and of a standardized meal on iron bioavailability from four popular prenatal multivitamin/multimineral supplements.

Iron absorption during an eight-hour period following ingestion of a multivitamin/multimineral formulation, both fasting and postprandial, after a standardized meal, was measured in five groups of 20 pregnant women (24-32 weeks of gestation) and statistically compared. The prenatal formulations were Natalins Rx, Prenatal 1/1, Stuartnatal Plus and Prenate 90. One-A-Day (without iron) was included in the study for the control group.

The descending order of absorption, both fasting and postprandial, were Prenate 90, Stuartnatal Plus, Prenatal 1/1 and Natalins Rx. Total iron absorption for each formulation group during the postprandial phase was higher than during the fasting phase. However, the net amount of iron absorption (in both the fasting and postprandial phases) from three of the four formulations (Stuartnatal Plus, Prenatal 1/1 and Prenate 90) provided the minimal 3.0 mg of supplemental iron per day recommended by the National Academy of Science.

The observed differences in iron absorption between prenatal supplements apparently reflect the effects of the various combinations of vitamins, essential minerals and additives. The absolute amount of elemental iron contained in a prenatal multivitamin/ multimineral formulation does not ensure availability.