The findings were reported Thursday at the American Stroke Association's International Stroke Conference in San Diego.
Nearly 5 percent of the participants in the trial suffered from stroke during an average of five years of follow-up. The risk was lower in patients who followed the vitamin regimen, although the researchers described the difference as "modest."
The study's statistics suggest the vitamin therapy would help 13 out of 1,000 subjects avoid a stroke.
Several groups gained more benefit from the vitamin treatment: people younger than 70, those who had higher cholesterol and homocysteine levels at the start of the study, those from areas without folic acid fortification in food, and those who weren't receiving antiplatelet drugs (such as Plavix) or cholesterol-lowering statins at the start of the study.
The vitamin therapy didn't appear to have an effect on the severity of stroke that some of the participants suffered.
Another study presented at the same meeting found that taking recommended doses of B vitamins reduced homocysteine levels and lowered the chances of another stroke in stroke patients.
The University of California, Los Angeles, researchers collected demographic, clinical and laboratory data on more than 3,000 stroke patients at the start of the study and in follow-up visits of six, 12 and 24 months.
The vitamin group was less likely to have a recurrent stroke by the end of the two-year study (13.4 percent vs. 20.3 percent), the team found
Vitamins aside, experts said a healthy diet is the best way to guard against stroke.
"The best anti-stroke diet is high in vegetables and fruits, including high-fiber produce, low in saturated and trans fat, and higher in plant-based unsaturated fats [such as olive oil, unsalted nuts and avocado], with enough calcium, potassium and omega-3 fatty acids and at a calorie level that helps maintain a healthy weight,"
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