Researchers studied 14 clinical trials involving nearly 50,000 participants. Of those participants, they found that people that took vitamin B had a 7 percent decreased risk of stroke compared with people that took a placebo.
Among the ones that did have strokes, taking vitamin B supplements did not appear to affect the severity of the strokes or the risk of dying from one.
Factors that may affect how vitamin B reduces stroke risk include the concentration and absorption of the supplement in a person's body. Patients with kidney disease or high blood pressure were also affected differently.
Dr. Xu Yuming, a study researcher and neurologist at Zhenzhou University in China, said the research is not enough information to go on.
"Previous studies have conflicting findings regarding the use of vitamin B supplements and stroke or heart attack," Yuming said. "Some studies have even suggested that the supplements may increase the risk of these events.
"Before you begin taking any supplements, you should always talk to your doctor."
While supplements containing B vitamins are thought to be safe, they should not be taken in large doses. High doses of niacin (B3) can cause health problems including blurred vision, nausea, vomiting and high blood sugar.