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Steady state folate concentrations achieved with 5 compared with 1.1 mg folic acid supplementation among women of childbearing age

¹ From the Department of Pharmaceutical Sciences, Leslie Dan Faculty of Pharmacy, University of Toronto, Toronto, Canada (PN, CT, and GK); The Motherisk Program, The Hospital for Sick Children, Toronto, ON, Canada (PN, CT, and GK); the Departments of Nutritional Sciences and Pathobiology and Laboratory Medicine, Faculty of Medicine, University of Toronto, Toronto, ON, Canada (DLO and BK); and the Department of Clinical Pathology, Sunnybrook Health Sciences Center, Toronto, ON, Canada (BK).

² Supported by Duchesnay Inc (Laval, PQ, Canada), which also supplied the prenatal multivitamins used in the study.

³ Address reprint requests and correspondence to G Koren, The Motherisk Program, The Hospital for Sick Children, 555 University Avenue, Toronto, ON M5G 1X8, Canada. E-mail: gideon.koren{at}sickkids.ca.

Background: Synthetic folic acid (0.4–1.0 mg) consumed during the periconceptional period has been shown to reduce the risk of neural tube defects. Women with poor supplement adherence or a previous pregnancy affected by a neural tube defect may need to take higher doses of folic acid (4–5 mg). However, there are limited data on the pharmacokinetics of higher folic acid doses.

Objective: Our aim was to compare steady state folate concentrations in women of childbearing age who took 5 or 1.1 mg folic acid daily for 30 wk.

Design: Forty nonpregnant women aged between 18 and 45 y, who did not take folic acid supplements, were enrolled in the study. Subjects were randomly assigned to take either 5 or 1.1 mg folic acid daily for 30 wk. Plasma and red blood cell (RBC) folate concentrations were measured at baseline and at weeks 2, 4, 6, 12, and 30.

Results: There was no significant difference in baseline RBC folate concentrations between the 2 groups (1121 ± 410 and 1035 ± 273 nmol/L for the 5- and 1.1-mg folic acid groups, respectively). Significant differences in RBC folate were detected between groups at weeks 4, 6, 12, and 30. RBC folate concentrations by week 30 were 2339 ± 782 and 1625 ± 339 nmol/L for the 5- and 1.1-mg folic acid groups, respectively.

Conclusion: The use of 5 mg folic acid among women of childbearing age produced higher blood folate concentrations, with a faster rate of folate accumulation, compared with 1.1 mg folic acid.