title: Folate status and homocysteine response to folic acid doses and withdrawal among young Chinese women in a large-scale randomized double-blind trial.
abstract: BACKGROUND
  There are no large randomized trials of the effect of folic acid dosing regimens on blood folate and homocysteine concentrations.
  
  
  OBJECTIVE
  We aimed to evaluate the changes in folate and homocysteine concentrations in response to different folic acid doses and to withdrawal in young women not exposed to other sources of folic acid.
  
  
  METHODS
  Women (n = 1108) were randomly assigned to 1 of 6 intervention groups for which daily intakes of folic acid for 6 mo were 100 microg 1 time/d, 25 microg 4 times/d, 400 microg 1 time/d, 100 microg 4 times/d, 4000 microg 1 time/d, or 4000 microg 1 time/wk. Plasma and red blood cell folate and homocysteine concentrations were measured at baseline; at 1, 3, and 6 mo; and 3 mo after the discontinuation of folic acid.
  
  
  RESULTS
  Folate and homocysteine concentrations were not different at baseline between the groups who had the same daily intake of folic acid as a single dose or multiple doses (P = 0.058). Plasma folate concentrations plateaued at 3 mo with 108% (95% CI: 97.7%, 120%), 259% (95% CI: 240%, 279%), 460% (95% CI: 417%, 503%), and 142% (95% CI: 123%, 162%) observed increases for the folic acid groups receiving 100, 400, and 4000 microg/d and 4000 microg/wk, respectively. The rate of reduction in folate concentrations during the 3 mo after cessation of folic acid was dose-dependent-higher intakes were associated with faster reductions.
  
  
  CONCLUSIONS
  Changes in folate and homocysteine concentrations were unaffected by different dosing schedules. After folic acid cessation, blood folate declined rapidly, which indicated that the intervention-enhanced folate status was rapidly diminished.
authors.affiliation: National Reference Laboratory on Reproductive and Child Health, Ministry of Health and National Center for Maternal and Infant Health, Peking University Health Science Center, Beijing, China.
authors.forename: Ling
authors.initials: L
authors.lastname: Hao
authors.forename: Quan-He
authors.initials: QH
authors.lastname: Yang
authors.forename: Zhu
authors.initials: Z
authors.lastname: Li
authors.forename: Lynn B
authors.initials: LB
authors.lastname: Bailey
authors.forename: Jiang-Hui
authors.initials: JH
authors.lastname: Zhu
authors.forename: Dale J
authors.initials: DJ
authors.lastname: Hu
authors.forename: Bo-Lan
authors.initials: BL
authors.lastname: Zhang
authors.forename: J David
authors.initials: JD
authors.lastname: Erickson
authors.forename: Le
authors.initials: L
authors.lastname: Zhang
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Gindler
authors.forename: Song
authors.initials: S
authors.lastname: Li
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Berry
mesh_terms: D000328:Adult; D019587:Dietary Supplements; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D004334:Drug Administration Schedule; D005260:Female; D005492:Folic Acid / Q000008:administration & dosage* / Q000097:blood*; D006710:Homocysteine / Q000097:blood* / Q000187:drug effects*; D006801:Humans; D009752:Nutritional Status
chemical_list: D006710:Homocysteine; D005492:Folic Acid