Effects of once-a-week or daily folic acid supplementation on red blood cell folate concentrations in women.
OBJECTIVE
Our aim was to determine if a once-a-week folic acid supplement increases women's red blood cell folate to concentrations (>905 nmol/l) that are associated with a low risk of bearing a child with a neural tube defect.


METHODS
Randomized control trial.


METHODS
General community.


METHODS
In total, 114 nonpregnant women (18-40 y) volunteers, with red blood cell folate concentrations between 295 and 905 nmol/l at screening.


METHODS
Women were randomized to receive a once-a-week 2800 microg folic acid supplement, a daily 400 microg folic acid supplement or a daily placebo for 12 weeks.


RESULTS
The mean (95% CI) red blood cell folate concentrations increased during the 12-week intervention from 608 (553-668) to 900 (828-978) in the weekly folic acid group (P<0.05) and from 615 (560-677) to 1053 (957-1158) nmol/l in the daily group (P<0.05) during the trial. At week 12, 49% of women ingesting the weekly folic acid supplement had red blood cell folate concentrations greater than 905 nmol/l compared to 74% of women ingesting the daily supplement.


CONCLUSIONS
A once-a-week 2800 microg folic acid supplement can increase women's red blood cell folate to concentrations associated with a reduced risk of bearing a child with a neural tube defect, but is less effective than a 400 microg daily supplement. Use of a weekly folic acid supplement over at least 12 weeks before conception by women of child-bearing age may prevent neural tube defects.


BACKGROUND
The Otago Medical Research Foundation (Laurenson Award). Healtheries (New Zealand) provided the supplements.
Department of Human Nutrition, University of Otago, Dunedin, New Zealand.
B
B
Norsworthy
C M
CM
Skeaff
C
C
Adank
T J
TJ
Green
D000328:Adult; D019587:Dietary Supplements; D004311:Double-Blind Method; D004334:Drug Administration Schedule; D004912:Erythrocytes / Q000737:chemistry*; D005260:Female; D005492:Folic Acid / Q000008:administration & dosage* / Q000097:blood*; D006801:Humans; D009436:Neural Tube Defects / Q000517:prevention & control; D016896:Treatment Outcome
D005492:Folic Acid