title: Bioavailability of food folates is 80% of that of folic acid.
abstract: 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.
  
  
  METHODS
  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.
authors.affiliation: Wageningen Centre for Food Sciences, Wageningen, Netherlands. renate.winkels@wur.nl
authors.forename: Renate M
authors.initials: RM
authors.lastname: Winkels
authors.forename: Ingeborg A
authors.initials: IA
authors.lastname: Brouwer
authors.forename: Els
authors.initials: E
authors.lastname: Siebelink
authors.forename: Martijn B
authors.initials: MB
authors.lastname: Katan
authors.forename: Petra
authors.initials: P
authors.lastname: Verhoef
mesh_terms: D000328:Adult; D004032:Diet; D004305:Dose-Response Relationship, Drug; D005260:Female; D005492:Folic Acid / Q000008:administration & dosage* / Q000138:chemical synthesis / Q000493:pharmacokinetics*; D005502:Food; D005504:Food Analysis; D006801:Humans; D008297:Male; D008875:Middle Aged; D009753:Nutritive Value
chemical_list: D005492:Folic Acid