Effect of Folic Acid and Betaine Supplementation on Flow-Mediated Dilation: A Randomized, Controlled Study in Healthy Volunteers
What this study found
Neither folic acid nor betaine improved flow-mediated dilation compared with placebo, despite clear homocysteine lowering. FMD changed by -0.1 FMD% (95% CI, -0.9 to 0.7) after folic acid and by -0.4 FMD% (-1.2 to 0.4) after betaine versus placebo, while plasma homocysteine fell by 20% (-2.0 umol/L, 95% CI -2.3 to -1.6) with folic acid and by 12% (-1.2 umol/L, -1.6 to -0.8) with betaine. No serious adverse events occurred. The authors concluded that lowering homocysteine did not affect vascular function in these healthy older volunteers.
- Study & population
- Healthy adults aged 50 to 70 years with higher-normal homocysteine and no cardiovascular disease or hypertension were recruited from volunteers at Wageningen University in Wageningen, the Netherlands.
- Intervention
- Two oral supplementation regimens were tested in a randomized, double-blind, crossover design for 6 weeks each: folic acid 0.8 mg/d mixed with 6 g lactose, taken twice daily in water, and betaine 6 g/d, also taken twice daily in water.
- Key limitation
- The trial was short, involved a relatively small sample of healthy older volunteers, and used a crossover design that limits broader generalizability.
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Open PDFOriginal abstract
Objectives: We investigated whether lowering of fasting homocysteine concentrations, either with folic acid or with betaine supplementation, differentially affects vascular function, a surrogate marker for risk of cardiovascular disease, in healthy volunteers. As yet, it remains uncertain whether a high concentration of homocysteine itself or whether a low folate status—its main determinant—is involved in the pathogenesis of cardiovascular disease. To shed light on this issue, we performed this study. Design: This was a randomized, placebo-controlled, double-blind, crossover study. Setting: The study was performed at Wageningen University in Wageningen, the Netherlands. Participants: Participants were 39 apparently healthy men and women, aged 50–70 y. Interventions: Participants ingested 0.8 mg/d of folic acid, 6 g/d of betaine, and placebo for 6 wk each, with 6-wk washout in between. Outcome Measures: At the end of each supplementation period, plasma homocysteine concentrations and flow-mediated dilation (FMD) of the brachial artery were measured in duplicate. Results: Folic acid supplementation lowered fasting homocysteine by 20% (−2.0 μmol/l, 95% confidence interval [CI]: −2.3; −1.6), and betaine supplementation lowered fasting plasma homocysteine by 12% (−1.2 μmol/l; −1.6; −0.8) relative to placebo. Mean (± SD) FMD after placebo supplementation was 2.8 (± 1.8) FMD%. Supplementation with betaine or folic acid did not affect FMD relative to placebo; differences relative to placebo were −0.4 FMD% (95%CI, −1.2; 0.4) and −0.1 FMD% (−0.9; 0.7), respectively. Conclusions: Folic acid and betaine supplementation both did not improve vascular function in healthy volunteers, despite evident homocysteine lowering. This is in agreement with other studies in healthy participants, the majority of which also fail to find improved vascular function upon folic acid treatment. However, homocysteine or folate might of course affect cardiovascular disease risk through other mechanisms.