To set the new dietary recommendation for vitamin B9 (folate), the ‘Dietary Folate Equivalent’ (DFE) has been used, reflecting the higher bioavailability of synthetic folic acid found in supplements and fortified foods compared to that of naturally occurring food folates (35).
Dietary Folate Equivalents (DFE):
Example: A serving of food containing 60 mcg folate would provide 60 mcg DFE, while a serving of pasta fortified with 60 mcg of folic acid would provide 1.7 x 60 = 102 mcg DFE due to the higher bioavailability of folic acid. A folic acid supplement of 400 mcg taken on an empty stomach would provide 800 mcg of DFE.
Note: DFEs were determined in studies with adults; thus, the use of DFEs to determine a folic acid requirement for infants would not be recommended.
Summary of Dietary Reference Values for folate
|Age||Males: µg DFE/day||Females: µg DFE/day|
|7-11 months (AI)||80 (AI)||80 (AI)|
|15 years and older||330||330|
|Life Stage||Age||Males: (mcg/day)||Females: (mcg/day)|
|Infants||0–6 months||65 (AI)||65 (AI)|
|Infants||7–12 months||80 (AI)||80 (AI)|
|Adults||19 years and older||400||400|
Because pregnancy is associated with a significant increase in cell division and other metabolic processes that require vitamin B9 (folate) coenzymes, the recommended dietary allowance (RDA) for pregnant women, established by the U.S. Food and Nutrition Board, is considerably higher than for women who are not pregnant (3).
However, the prevention of neural tube defects (NTD) was not considered when setting the RDA for pregnant women because the crucial events in the development of the neural tube occur before many women are aware that they are pregnant (10).
As the available scientific evidence shows that adequate vitamin B9 (folate) intake prevents neural tube defects, helps in lowering the risk of some forms of cancer, and may lower the risk of cardiovascular diseases, many experts recommend that adults take a 400 micrograms (mcg) supplement of folic acid daily, in addition to folate and folic acid consumed in the diet. Even with a larger than average intake of folic acid from fortified foods, it is unlikely that an individual's daily folic acid intake would regularly exceed the tolerable upper intake level of 1,000 micrograms (= 1 mg)/day (see Safety).
For a detailed overview of recommended daily intakes (PRIs/RDAs) of vitamins and minerals for adults derived from different countries and organizations see PDF.
A common variation in the gene for the vitamin B9 (folate) coenzyme-dependent enzyme ‘methylene tetrahydrofolate reductase’ (MTHFR) results in a less stable enzyme (37), required to form methionine from homocysteine. When folate intake is low, individuals with the abnormal gene have lower levels of the MTHFR enzyme and thus higher levels of homocysteine in their blood (38). Improved folate nutritional status appears to stabilize the MTHFR enzyme, resulting in improved enzyme levels and lower homocysteine levels. An important unanswered question about folate is whether the present RDA is enough to normalize MTHFR enzyme levels in individuals with the genetic variation.
Authored by Dr Peter Engel in 2010, reviewed and revised by Angelika Friedel on 29.06.2017