Folate status and homocysteine response to folic acid doses and withdrawal among young Chinese women in a large-scale randomized double-blind trial.
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.
Hao
Ling
L
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.
Yang
Quan-He
QH
Li
Zhu
Z
Bailey
Lynn B
LB
Zhu
Jiang-Hui
JH
Hu
Dale J
DJ
Zhang
Bo-Lan
BL
Erickson
J David
JD
Zhang
Le
L
Gindler
Jacqueline
J
Li
Song
S
Berry
Robert J
RJ
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
D006710:Homocysteine; D005492:Folic Acid