New research suggests folic acid could significantly reduce stroke risk in patients with high blood pressure who are taking the hypertension medication enalapril.

Stroke is the second leading cause of death in the world, and primary prevention is crucial in lowering the incident rate, the Journal of the American Medical Association (JAMA) reported.

The recent study looked at 20,000 adults in China who had high blood pressure but no history of heart attack or stroke. The researchers determined the combined use of enalapril and folic acid lowered stroke risk when compared to the use of enalapril alone. The participants were tested for variations in the MTHFR C677T gene (CC, CT, and TT genotypes), which can influence folate levels.

During a median treatment duration of 4.5 years, strokes occurred in 2.7 percent of the enalapril-folic acid group compared with 3.4 percent of participants who took enalapril alone, representing an absolute risk reduction of 0.7 percent and a relative risk reduction of 21 percent. Participants who took folic acid also saw a reduced risk of ischemic stroke and composite cardiovascular events.

The findings suggest baseline folate level is an important determinant of the role they play in stroke prevention and therapy.

"In this population without folic acid fortification, we observed considerable individual variation in plasma folate levels and clearly showed that the beneficial effect appeared to be more pronounced in participants with lower folate levels," the researchers wrote.

The researchers noted that due to "limited and inconsistent" data there is still uncertainty remains on the efficacy of folic acid therapy for the primary prevention of stroke.

"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," the researchers wrote.

The findings were published in a recent edition of JAMA.