Lowering homocysteine levels through vitamin B supplementation may modestly help reduce stroke risk, a meta-analysis suggested.
In an analysis that included 14 randomized controlled trials with 54,913 participants, the use of vitamin B supplements decreased homocysteine levels by 1.3 to 10.4 mmol/L, as expected from the various doses given, according to Yuming Xu, MD, of First Affiliated Hospital of China's Zhengzhou University, and colleagues.
And the risk of stroke was 7% lower overall with B vitamin supplements (RR 0.93, 95% CI 0.86-1, P=0.04), the researchers reported online in Neurology. The effect on stroke risk appeared of borderline significance in the absence of folate (vitamin B9) fortification of grain products, but wasn't significant for populations already getting the vitamin in their food supply, they noted.
Other factors associated with modest benefit included high blood pressure and low antiplatelet usage. "All three of these factors do not apply to the typical stroke-prone patient seen in the U.S. clinic," commented James Meschia, MD, chair of neurology at the Mayo Clinic in Jacksonville, Fla.
He also cautioned about some surprising findings: How much B vitamin was given, baseline homocysteine levels, and how much homocysteine subsequently dropped didn't seem to have an impact on stroke. That was unexpected, given that the proposed mechanism of stroke reduction is homocysteine lowering.
"Until we can understand why these particular subgroups do not seem to matter, it does call into question how compelling the finding is that B vitamin supplementation lowers stroke risk," Meschia said. Regardless, a 7% relative reduction of patients' typically 1% to 2% annual stroke risk probably wouldn't be enough to influence practice, he told MedPage Today. Prior trials and meta-analyses cast doubt on folic acid benefits in cardiovascular prevention overall.
