title: [6S]5-methyltetrahydrofolate or folic acid supplementation and absorption and initial elimination of folate in young and middle-aged adults.
abstract: OBJECTIVE
  To assess the effects of supplementation with the diastereoisomer of 5-methyltetrahydrofolate ([6S]5-methylTHF), as an alternative supplement for folic acid, on folate absorption and elimination, in two age groups.
  
  
  METHODS
  A randomized, double-blind intervention study.
  
  
  METHODS
  A total of 12 young (<30 y) and 12 middle-aged (> or =50 y) healthy volunteers were recruited.
  
  
  METHODS
  Volunteers were randomized to receive daily supplementation with 400 mug folic acid or equimolar amounts of [6S]5-methylTHF during 5 weeks. Before and after supplementation, absorption and initial elimination were calculated following oral [(2)H(2)]folic acid test doses using isotope kinetics in plasma.
  
  
  RESULTS
  Folic acid absorption was lower in the middle-aged as compared to the young adults, both before (P = 0.03) and after (P = 0.05) supplementation. In the young adults, absorption decreased by 22% after [6S]5-methylTHF and increased by 21% after folic acid (P = 0.02). In the other age group, no such changes were found. The folate rate constant of elimination increased after folic acid supplementation in the young (+50%; P = 0.05) but not in the middle-aged (+18%; P = 0.5) adults.
  
  
  CONCLUSIONS
  Young adults show increased folate turnover after folic acid supplementation relative to the effect of [6S]5-methylTHF supplementation. Similar differences are not observed in middle-aged adults, in whom folic acid absorption was found to be lower as compared to the young adults.
  
  
  BACKGROUND
  Financial support was received from the European Union 5th Framework Programme (Grant QLRT-1999-00576).
authors.affiliation: Department of Clinical Chemistry, Institute for Cardiovascular Research, VU University Medical Center, Amsterdam, The Netherlands. novosilski@hotmail.com
authors.forename: K
authors.initials: K
authors.lastname: de Meer
authors.forename: Y M
authors.initials: YM
authors.lastname: Smulders
authors.forename: J R
authors.initials: JR
authors.lastname: Dainty
authors.forename: D E C
authors.initials: DE
authors.lastname: Smith
authors.forename: R M
authors.initials: RM
authors.lastname: Kok
authors.forename: C D A
authors.initials: CD
authors.lastname: Stehouwer
authors.forename: P M
authors.initials: PM
authors.lastname: Finglas
authors.forename: C
authors.initials: C
authors.lastname: Jakobs
mesh_terms: D000328:Adult; D000375:Aging / Q000097:blood / Q000378:metabolism*; D019540:Area Under Curve; D018592:Cross-Over Studies; D019587:Dietary Supplements; D004311:Double-Blind Method; D005260:Female; D005492:Folic Acid / Q000008:administration & dosage* / Q000493:pharmacokinetics*; D006710:Homocysteine / Q000097:blood; D006801:Humans; D007408:Intestinal Absorption / Q000187:drug effects*; D008297:Male; D008875:Middle Aged; D013763:Tetrahydrofolates / Q000008:administration & dosage / Q000493:pharmacokinetics
chemical_list: D013763:Tetrahydrofolates; D006710:Homocysteine; D005492:Folic Acid; C005984:5-methyltetrahydrofolate