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Bioavailability of food folates is 80% of that of folic acid^1,2,3

¹ From the Wageningen Centre for Food Sciences, Wageningen, Netherlands (RMW, IAB, MBK, and PV), and the Division of Human Nutrition, Wageningen University, Wageningen, Netherlands (RMW, IAB, ES, MBK, and PV)

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 µg food folate/d and a placebo capsule; groups B, C, and D (n = 14 or 15) received a low-folate diet with 73 µg food folate/d and folic acid capsules. These capsules contained 92 µg folic acid/d for group B, 191 µg for group C, and 289 µg for group D. In addition, all 72 subjects daily ingested a capsule with 58 µg [¹³C₁₁]-labeled folic acid. We measured the percentage of [¹³C₁₁]-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 [¹³C₁₁]-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 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.

Key Words: Food folate • bioavailability • folic acid • stable isotopes