The meta-analysis, published in Neurology, analysed pooled data from almost 55,000 people in 14 randomised controlled trials in order to test for a potential benefit of B vitamin supplementation on cerebrovascular disease risk via lowering homocysteine.
"Previous studies have conflicting findings regarding the use of vitamin B supplements and stroke or heart attack," explained study author Xu Yuming, of Zhengzhou University, China.
"Some studies have even suggested that the supplements may increase the risk of these events," he said.
However, by pooling together the data from previous trial, the team revealed that taking vitamin B supplements may help reduce the risk of stroke compared to placebo or a lower dose of vitamin B.
Indeed Yuming and his colleagues revealed that vitamin B was found to lower the overall risk of stroke in the studies by 7%. However, supplementation did not appear to affect the severity of strokes or risk of death from stroke, they added.
The team analysed data from 14 randomized clinical trials with a total of 54,913 participants. Participants were then followed for a minimum of six months, and all of the studies compared B vitamin use with a placebo or a very low-dose B vitamin.
During the follow up period of all studies the team found 2,471 incidence of stroke, all of which showed some benefit of taking vitamin B.
“We observed a reduction in overall stroke events resulting from reduction in homocysteine levels following B vitamin supplementation, but not in subgroups divided according to primary or secondary prevention measures, ischemic vs hemorrhagic stroke, or occurrence of fatal stroke,” explained Yuming and his team.
They also revealed that folic acid - a supplemental form of vitamin B9 (folate) - which is often found in fortified cereals, appeared to reduce the effect of vitamin B, while intake of vitamin B12 was not associated with a reduction in stroke risk.
"Based on our results, the ability of vitamin B to reduce stroke risk may be influenced by a number of other factors such as the body's absorption rate, the amount of folic acid or vitamin B12 concentration in the blood, and whether a person has kidney disease or high blood pressure," said Yuming.
Published online ahead of print, doi: 10.1212/WNL.0b013e3182a823cc
“Vitamin B supplementation, homocysteine levels, and the risk of cerebrovascular disease”
Authors: Yan Ji, Song Tan, Yuming Xu, et al