Effect of Folic Acid and Betaine Supplementation on Flow-Mediated Dilation: A Randomized, Controlled Study in Healthy Volunteers

PLoS Clinical Trials

Jun 2006

DOI: 10.1371/journal.pctr.0010010

Citations:42

Influential Citations:3

Interventional (Human) Studies

Enhanced Details

Methods

Healthy men and women aged 50-70 years; no cardiovascular disease or hypertension; not using vitamin B supplements more than once weekly in the 3 months before entry; 40 participants randomized to six treatment sequences in a double-blind, placebo-controlled, crossover design; 39 completed.

Intervention

Betaine 6 g/day (3 g after breakfast and 3 g after dinner) dissolved in water; Folic acid 0.8 mg/day mixed with 6 g lactose; Placebo: 6 g lactose; all supplements taken twice daily after meals; duration per supplement: 6 weeks.

Results

Folic acid lowered fasting homocysteine by 2.0 µmol/L (20%) vs placebo; betaine lowered by 1.2 µmol/L (12%) vs placebo. FMD did not change with either supplement relative to placebo (folic acid difference: −0.1 FMD% [95% CI −0.9 to 0.7]; betaine difference: −0.4 FMD% [95% CI −1.2 to 0.4]). Conclusion: Neither long-term folic acid nor betaine supplementation improves vascular function in healthy elderly adults, despite effective homocysteine lowering.

Limitations

Small sample size (n=40; 39 completed); short duration per treatment (6 weeks); outcomes are surrogate markers (FMD) rather than clinical cardiovascular endpoints; results in healthy elderly population may not generalize to patients with cardiovascular disease.

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. show less