Source: Lancet 369: 1876-1882
Article Type: Meta Analysis
Authors: X Wang et al.

More than a decade ago, homocysteine has been suggested to act as an independent risk factor for the development of cardiovascular disease (CVD). Luckily, homocysteine levels can easily be modified, i.e. reduced, in states of adequate folic acid/folate (FA) intake. Whereas nobody doubts that FA supplementation is able to significantly reduce homocysteine levels in humans, there is an ongoing debate of whether homocysteine is indeed a risk factor or an innocent bystander.
The recent meta analysis by Wang an colleagues argues for a beneficial effect of FA supplementation on human health, here stroke prevention. The risk of stroke was reduced by 18% and the effect of FA supplementation was greater in those studies with longer duration. Although this meta analysis aimed to establish a link between FA supplementation and primary stroke prevention, there are several confounders that ought to be considered (for details see CM Carlsson’s comment, Lancet 369). To get a better picture of the true potential of increasing FA intake in terms of health outcome, I also recommend reading another meta analysis which has been published in 2006 in JAMA 296 and confirmed that FA supplementation did not reduce the risk of CVD or all-cause mortality in patients with pre-existing disease.
Last but not least, for all who would like to get a quick overview on homocysteine, you might want to go to the following wepage www.homocysteine.net run by Axis-Shield, a diagnostic company based in the UK.

Image taken from: strokecenter.org