Background: Increased plasma total homocysteine (tHcy) is a risk factor for vascular disease and adverse pregnancy outcomes. Health authorities recommend periconceptional supplementation with 400 micro g folic acid to prevent neural tube defects. Several countries have implemented food fortification with folic acid. However, excessive intake of folic acid could mask an undiagnosed vitamin B-12 deficiency. The biologically active [6S]-5-methyltetrahydrofolate ([6S]-5-MTHF) may be an alternative to folic acid because it is unlikely to mask vitamin B-12 deficiency symptoms.

Objective: We compared the tHcy-lowering potential of 2 dosages of [6S]-5-MTHF with that of 400 micro g folic acid during 24 wk of supplementation.

Design: In this double-blind, randomized, controlled intervention trial, 144 female participants were supplemented daily with 400 micro g folic acid, 416 micro g [6S]-5-MTHF, 208 micro g [6S]-5-MTHF, or placebo. Concentrations of tHcy and plasma folate were measured at baseline and at 4-wk intervals.

Results: After supplementation, there was a significant interaction between time and treatment with respect to changes in tHcy and plasma folate (both P < 0.001 by two-factor repeated-measures analysis of variance). The decrease in tHcy did not differ significantly between the 3 supplemented groups (P > 0.05; Tukey's post hoc test). The increase in plasma folate in the group receiving 208 micro g [6S]-5-MTHF was significantly lower than that in the groups receiving 400 micro g folic acid (P < 0.001) or 416 micro g [6S]-5-MTHF (P < 0.05).

Conclusions: [6S]-5-MTHF was shown to be an adequate alternative to folic acid in reducing tHcy concentrations. Supplementation with 416 micro g [6S]-5-MTHF was no more effective than that with 208 micro g [6S]-5-MTHF.