The bioavailabilities of iron and folic acid in supplements may be an area of concern, primarily due to the higher requirements during pregnancy. Materna® contains a large quantity of calcium (250 mg), whereas Sprinkles contains none. A study by Hallberg, et al. (1991) showed that adding as little as 165 mg of calcium to a meal reduced the absorption of iron by 50-60% in wheat rolls. In addition, a study by Koren, et al. (2004) showed that after adjusting for dose, the iron absorbed from one maternal iron supplement containing calcium was statistically less as compared to one without calcium. A study by Rossander-Hultén et al (1991, as cited by Sandröm, 2001) found that zinc has the potential to inhibit iron absorption in supplements but not when zinc is added to food . The iron supplement contains 25mg of zinc whereas SuppleFem contains only 5.5mg. There are no reported interactions between folate and other nutrients. However, there is evidence that folate bioavailability may be influenced by the amount ingested. While pregnancy does increase the demand for folate, the amount in SuppleFem is compliant with the current DRI guidelines at 600µg, whereas the iron supplement contains 1000 µg. Currently, there is not enough research to indicate whether unmetabolized folic acid poses any health risks .