Bioavailability of food folates is 80% of that of folic acid

Am J Clin Nutr. 2007 Feb;85(2):465-73. doi: 10.1093/ajcn/85.2.465.


Background: The bioavailability of natural food folates is lower than that of synthetic folic acid, but no agreement exists as to the extent of the difference.

Objective: In a 4-wk dietary intervention study, we determined the aggregate bioavailability of food folates from fruit, vegetables, and liver relative to that of folic acid.

Design: Seventy-two healthy adults were randomly divided into 4 treatment groups. Group A (n = 29) received a high-folate diet with 369 mug food folate/d and a placebo capsule; groups B, C, and D (n = 14 or 15) received a low-folate diet with 73 microg food folate/d and folic acid capsules. These capsules contained 92 microg folic acid/d for group B, 191 microg for group C, and 289 microg for group D. In addition, all 72 subjects daily ingested a capsule with 58 microg [(13)C(11)]-labeled folic acid. We measured the percentage of [(13)C(11)]-labeled folate in plasma folate at the end of the intervention and ascertained the changes in serum folate concentrations over the 4 wk of the intervention.

Results: Bioavailability of food folate relative to that of folic acid was 78% (95% CI: 48%, 108%) according to [(13)C(11)]-labeled folate and 85% (52%, 118%) according to changes in serum folate concentrations.

Conclusions: The aggregate bioavailability of folates from fruit, vegetables, and liver is approximately 80% of that of folic acid. The consumption of a diet rich in food folate can improve the folate status of a population more efficiently than is generally assumed.

Publication types

  • Comparative Study
  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Diet*
  • Dose-Response Relationship, Drug
  • Female
  • Folic Acid / administration & dosage*
  • Folic Acid / chemical synthesis
  • Folic Acid / pharmacokinetics*
  • Food Analysis
  • Food*
  • Humans
  • Male
  • Middle Aged
  • Nutritive Value


  • Folic Acid