Taking vitamin B supplements may help reduce the risk of stroke, a new review suggests.
Researchers looked at 14 clinical trials involving nearly 50,000 participants, and found that people who took vitamin B had a 7 percent decreased risk of stroke compared with people who took a placebo.
However, among those who did have strokes, taking vitamin B supplements did not appear to affect the severity of strokes or the risk of dying from a stroke, according to the study, published Sept. 18 in the journal Neurology.
A number of factors may influence the ability of vitamin B to reduce a person's stroke risk, the researchers said. These factors include how well a person's body absorbs the vitamins, the concentrations of vitamins in the blood and whether a person has kidney disease or high blood pressure, said study researcher Dr. Xu Yuming, a neurologist at Zhengzhou University in China.
"Before you begin taking any supplements, you should always talk to your doctor," Yuming said.
In a stroke, the blood supply to the brain is interrupted by a blood clot or the bursting of a blood vessel. Common risk factors for stroke include high blood pressure, high cholesterol and smoking.
However, previous studies indicate that these risk factors explain only half of the risk for stroke, the researchers said. Some studies have suggested that high levels of the amino acid homocysteine in the blood could potentially be a risk factor for vascular disease, which prompted researchers to examine whether vitamin B supplements could reduce homocysteine levels and, in turn, lower stroke risk. But such studies have found mixed results.
"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."
B vitamins are important nutrients for the body. They can be found in a variety of foods, including whole grains, potatoes, bananas, beans and lentils.
The American Cancer Society notes that while supplements containing B vitamins are generally thought to be safe, they should not be taken in large doses. High doses of vitamin B3 (niacin) can cause health problems including blurred vision, nausea, vomiting and high blood sugar.