Integrating the issues of folate bioavailability, intake and metabolism in the era of fortification

The addition of folic acid to foods in the United States, Canada and several other countries has yielded improved folate nutritional status and reduced the incidence of neural tube defects. In spite of this success, a number of questions remain regarding the bioavailability of natural and added folates and the level of folate intake from dietary sources needed to meet nutritional requirements. Many aspects of current folate requirements are being expressed in terms of dietary folate equivalents, in which an adjustment is employed to account for differences in mean bioavailability of natural and added forms of folate. In this review, we discuss the scientific rationale behind such assumptions and research needs in the broad area of folate bioavailability. We also consider the merits of fortification strategies, including the biofortification of foods.