A meta-analysis of folic acid supplementation studies has found a positive impact on an important cardiovascular disease risk factor. This suggests that high doses of folic acid could be useful in cardiovascular disease prevention.

Observational studies have linked folic acid consumption with better heart health but it is not clear how folic acid may be exerting an effect. Researchers from the Netherlands searched for all high quality studies that tested the impact of folic acid supplementation on flow-mediated dilation (FMD). FMD is a popular means of assessing the flexibility of blood vessels. Decreased flexibility is a risk factor for cardiovascular disease as it can adversely affect blood pressure. It could be that folic acid helps to maintain normal FMD, which then lowers cardiovascular disease risk.

The researchers found 14 randomised, double-blind placebo trials that met their inclusion criteria. These were published between 1966 and 2005 and represented data on 732 subjects. A meta-analysis discovered that folic acid supplementation improved FMD by a small but significant amount (1.08 percentage points). Higher doses of folic acid, i.e. 10,000 µg/d, had a greater impact on FMD than doses closer to the labelling Recommended Daily Amount of 200 µg/d. However, the researchers suggested that the dose-response data should be treated with caution due to statistical limitations. In conclusion, it would appear that folic acid may be useful in cardiovascular disease prevention but very high doses are needed to produce a clinically significant effect.

For more information, see
de Bree A et al (2007). Folic acid improves vascular reactivity in humans: a meta-analysis of randomized controlled trials. American Journal of Clinical Nutrition, Vol 86, pp 610-617.

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