Vitamin B9 // Folic Acid

Vitamin B9 Intake Recommendations

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):

  • 1 microgram (mcg) food folate provides 1 mcg DFE
  • 1 mcg folic acid taken with meals or as fortified food provides 1.7 mcg DFE
  • 1 mcg folic acid (supplement) taken on an empty stomach provides 2 mcg 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.

In 2015, the European Scientific Committee for Food adopted the population reference intakes (PRI) for vitamin B9 (folate) (36):

Summary of Dietary Reference Values for folate

 Age    Males: µg DFE/day Females: µg DFE/day
 7-11 months (AI) 80 (AI) 80 (AI)
 1–3 years 120 120
 4–6 years 140 140
 7–10 years 200 200
 11–14 years 270 270
 15 years and older 330 330
 Pregnant - 600
 Breast feeding - 500

AI = average intake
DFE = dietary folate equivalent

In 1998, the U.S. Food and Nutrition Board established recommended dietary allowance (RDA) values for vitamin B9 (folate) in Dietary Folate Equivalents (DFE) that should meet the dietary requirement (1):

 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)
 Children  1–3 years 150 150
 Children  4–8 years 200 200
 Children 9–13 years 300 300
 Adolescents 14–18 years 400 400
 Adults 19 years and older 400 400
 Pregnancy all ages - 600
 Breast-feeding all ages - 500

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.

Genetic variation

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