Relative bioavailability of iron and folic acid from a new powdered supplement compared to a traditional tablet in pregnant women

Abstract

Background: Deficiencies of iron and folic acid during pregnancy can lead to adverse outcomes for the fetus, thus supplements are recommended. Adherence to current tablet-based supplements is documented to be poor. Recently a powdered form of micronutrients has been developed which may decrease side-effects and thus improve adherence. However, before testing the efficacy of the supplement as an alternate choice for supplementation during pregnancy, the bioavailability of the iron needs to be determined. Our objective was to measure the relative bioavailability of iron and folic acid from a powdered supplement that can be sprinkled on semi-solid foods or beverages versus a traditional tablet supplement in pregnant women.

Methods: Eighteen healthy pregnant women (24 - 32 weeks gestation) were randomized to receive the supplements in a crossover design. Following ingestion of each supplement, the changes (over baseline) in serum iron and folate over 8 hours were determined. The powdered supplement contained 30 mg of iron as micronized dispersible ferric pyrophosphate with an emulsifier coating and 600 mug folic acid; the tablet contained 27 mg iron from ferrous fumarate and 1000 mug folic acid.

Results: Overall absorption of iron from the powdered supplement was significantly lower than the tablet (p = 0.003). There was no difference in the overall absorption of folic acid between supplements. Based on the differences in the area under the curve and doses, the relative bioavailability of iron from powdered supplement was lower than from the tablet (0.22).

Conclusion: The unexpected lower bioavailability of iron from the powdered supplement is contrary to previously published reports. However, since pills and capsules are known to be poorly accepted by some women during pregnancy, it is reasonable to continue to explore alternative micronutrient delivery systems and forms of iron for this purpose.

Trial registration: ClinicalTrials.gov NCT00789490.

Figure 1

Study Flow Diagram.

Figure 2

Mean incremental changes in serum iron concentrations between tablet and powdered supplements. Mean (± SEM) incremental changes in serum iron concentration in pregnant subjects over 8 hours after administration of either 27 mg of iron from ferrous fumarate in a traditional tablet supplement or 30 mg of iron from micronized dispersible ferric pyrophosphate in powdered supplement sprinkled over a standard meal. n = 17. The curve was adjusted for basal (diurnal) variation and the iron content of the standardized meal. There was a significant difference (p = 0.0003) between the relative bioavailability (as measured using AUC) of the iron in tablet supplement (41.8 ± 45.9 μmol·h/L) when compared to the iron in the powdered supplement (10.0 ± 43.3 μmol·h/L). The data were analyzed with the use of mixed-model repeated-measures with age, gestational age, ferritin concentration and parity as fixed effects and subject as the repeated effect. The pair-wise differences of least-square means of the treatments were tested with the use of Tukey-Kramer p value adjustments.

Figure 3

Mean incremental changes in plasma folate concentrations between tablet and powdered supplements. Mean (± SEM) changes in plasma folate concentrations in pregnant subjects over 8 hours after administration of either 1000 μg folic acid in the traditional tablet supplement or 600 μg folic acid in the powdered supplement sprinkled over a standard meal. n = 18. There was no significant difference in the area under the folate absorption curve in the tablet supplement (248.7 ± 140.2 nmol·h/L) when compared to the folic acid in the powdered supplement (271.8 ± 110.9 nmol·h/L). The data were analyzed with the use of mixed-model repeated measures with age, gestational age, ferritin concentration and parity as fixed effects and subject as the repeated effect. The pair-wise differences of least-square means of the treatments were tested with the use of Tukey-Kramer P value adjustments.