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Determining bioavailability of food folates in a controlled intervention study
Mary P Hannon-Fletcher1, Nicola C Armstrong, John M Scott
1Northern Ireland Centre for Food and Health and the School of Hotel, Leisure, and Tourism, University of Ulster, Coleraine, United Kingdom. p.hannon@ulster.ac.uk
The American Journal of Clinical Nutrition
|September 28, 2004
Summary
Folic acid is more bioavailable than natural food folates like spinach and yeast. These findings support the current dietary folate equivalents (DFE) system used in the United States.
Area of Science:
- Nutritional Science
- Biochemistry
Background:
- Dietary folate equivalents (DFEs) account for differing bioavailability of natural food folates and synthetic folic acid.
- Previous bioavailability studies are limited by confounding factors.
Purpose of the Study:
- Compare bioavailability of food folates versus folic acid under controlled conditions.
- Utilize spinach (50% polyglutamyl folate) and yeast (100% polyglutamyl folate) as natural folate sources.
Main Methods:
- 96 men were randomized into 4 groups over 30 days.
- Intervention groups received placebo, folic acid, spinach folate, or yeast folate.
- Plasma homocysteine (tHcy) levels and serum folate were monitored.
Main Results:
- Folic acid significantly increased serum folate and lowered tHcy compared to placebo.
- Spinach and yeast folates did not show significant changes.
- Bioavailability of natural folates was 30-59% compared to folic acid.
Conclusions:
- Relative bioavailability estimates align with those used for US DFE calculations.
- Folic acid demonstrates superior bioavailability over natural food folates.