A meta-analysis found folate supplementation reduced the risk of stroke by 18%, a significant benefit compared with placebo. An analysis of study characteristics suggested that trials lasting over 36 months demonstrated a significant benefit for folate therapy with a reduce risk of 29% compared to placebo. In addition, compared to placebo, folate was effective only in areas without or with very little grain enrichment (25% reduced risk), where homocysteine was lowered by more than 20% (23% reduced risk), and among patients without a previous history of stroke (25% reduced risk). (11)
Lowering of homocysteine, an amino acid, with folic acid and vitamins B6 and B12 had a modest, but beneficial effect on stroke prevention or fatal stroke among a population at high risk for cardiovascular disease. Results from this five-year research trial that randomly assigned 5,522 adults with heart disease to either placebo or a daily combination regimen of 2.5 mg. of folic acid (vitamin B9), 50 mg vitamin B6 and 1mg of vitamin B12 found that daily supplements of folic acid, vitamin B6, and B12 for 5 years reduced the risk of stroke by 25%. However, no noticeable effect was observed during the first 3 years of supplementation. During a five-year follow-up period, stroke occurred in 258 of the participants (4.7%). The risk was lower in those who followed the vitamin regimen. The average homocysteine concentration decreased by 2.2 micromol/L in the vitamin therapy group, and increased by 0.80 micromol/L in the placebo group. Those who benefited the most from the vitamin treatment included those younger than age 69, with higher cholesterol and homocysteine levels at the start of the study, from areas where folic acid-fortified food isn’t available, and who weren’t receiving anti-platelet drugs or cholesterol-lowering drugs at the start of the study. (8)