The 1998 recommendations for folate are expressed using a term called the dietary folate equivalent (DFE). The DFE was developed to help account for the difference in bioavailability between naturally occurring dietary folate and synthetic folic acid. The Food and Nutrition Board of the US National Academy of Sciences reasoned that, since folic acid in supplements or in fortified food is 85% bioavailable, but food folate is only about 50% bioavailable, folic acid taken as supplements or in fortified food is 85/50 (i.e., 1.7) times more available. Thus, the calculation of the DFE for a mixture of synthetic folic acid and food is mg of DFE = mg food folate + (1.7 x mg synthetic folate).
International recommendation tables are constantly subject to review, particularly in view of the relationship between folate status and the risk of NTD and specific chronic diseases including coronary artery disease and colorectal cancer.
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