In people with high blood pressure, folic acid supplementation alongside a common hypertension medication was found to reduce first-time stroke risk.
Each year, more than 795,000 people in the US have a stroke. Of these, around 610,000 are first-time strokes.
High blood pressure, or hypertension, is a known risk factor for stroke. According to the Centers for Disease Control and Prevention (CDC), around 8 in 10 first-time strokes are among people with high blood pressure.
Past studies looking at the effects of folic acid supplementation for prevention of cardiovascular disease have indicated that the vitamin may be effective for reducing stroke risk. But the investigators of this latest research - including Dr. Yong Huo of Peking University First Hospital in Beijing, China - say no studies have had stroke as the primary outcome, making it difficult to make a firm connection between the two.
As such, the team set out to assess the link between folic acid supplementation and stroke risk among 20,702 adults from China aged 45-75 years. All adults had hypertension, but they had no history of stroke or heart attack at study baseline.
Variations in the MTHFR C677T genotypes (CC, CT or TT) - which can affect folate levels - were assessed among participants, and their folate levels were measured at study baseline.
Between May 2008 and August 2013, participants were randomized to receive either 10 mg of enalapril - a drug commonly used to treat high blood pressure - and 8 mg of folic acid daily, or a daily 10 mg dose of enalapril alone.
Folic acid is a B vitamin that the body needs for healthy cell production. A lack of folic acid can lead to anemia and other health complications. It is highly recommended that women increase their intake of folic acid prior to and during pregnancy, as studies have suggested it can significantly reduce the risk of major birth defects, such as spina bifida and anencephaly.
Treatment with folic acid and enalapril reduced stroke risk by 21%
During the median 4.5-year follow-up period, 282 (2.7%) participants who were treated with both enalapril and folic acid had a first stroke, compared with 355 (3.4%) participants treated with enalapril.
The team calculated that participants treated with both enalapril and folic acid were at 21% lower risk of stroke, compared with participants treated with enalapril alone. Treatment with enalapril and folic acid also represented a 0.7% reduction in absolute risk of first-time stroke, the researchers found.
A lower relative risk of ischemic stroke was also identified among participants treated with enalapril and folic acid, and these participants were also at lower risk of combinations of cardiovascular events, including heart attack, stroke and cardiovascular death.
The team found that participants with TT genotypes were most likely to benefit from combination treatment with enalapril and folic acid, as were participants who had low folate levels at study baseline.
Commenting on their findings, the authors say:
"We speculate that even in countries with folic acid fortification and widespread use of folic acid supplements, such as in the United States and Canada, there may still be room to further reduce stroke incidence using more targeted folic acid therapy - in particular, among those with the TT genotype and low or moderate folate levels."
In an editorial linked to the study, Dr. Meir Stampfer and Dr. Walter Willet, of the Harvard T. H. Chan School of Public Health and Channing Division of Network Medicine in Boston, MA, say these findings hold important implications for the prevention of stroke across the globe, noting that the results are also likely to apply to populations without high blood pressure.
"Ideally, adequate folate levels would be achieved from food sources such as vegetables (especially dark green leafy vegetables), fruits and fruit juices, nuts, beans and peas. However, for many populations, achieving adequate levels from diet alone is difficult because of expense or availability," they add.
"This study seems to support fortification programs where feasible, and supplementation should be considered where fortification will take more time to implement."
Last month, Medical News Today reported on a study claiming that sleeping for more than 8 hours each night may increase the risk of stroke by 46%.