B vitamin effect applies to those with certain factors
According to the National Institutes of Health (NIH) certain B vitamins (folic acid, vitamin B12, and vitamin B6) might reduce cardiovascular disease risk by lowering homocysteine levels.
Dr. Yuming Xu, MD, Department of Neurology, The First Affiliated Hospital of Zhengzhou University, and colleagues from the The First Affiliated Hospital of Zhengzhou University and the Medical College of ZhengZhou University (A.C.), Zhengzhou, Henan, China, carried out a meta-analysis on the effect of lowering homocysteine levels via B vitamin supplementation on cerebrovascular disease risk.
Researchers used clinical trials published before August 2012. This analysis included 14 randomized controlled trials with 54,913 participants aged 52 to 68.9 years, and had compared vitamin B to a placebo, very low dose B vitamins or usual care. The study follow-up ranged from 24 t 87 months.
The researchers found that among the trials there were 2,471 stroke events. There was a reduction in overall stroke events resulting from reduction in homocysteine levels following B vitamin supplementation (RR 0.93; 95% CI 0.86–1.00; p = 0.04), but not in subgroups divided according to primary or secondary prevention measures, ischemic vs hemorrhagic stroke, or occurrence of fatal stroke.
For stroke, subgroup analyses showed the following borderline and significant associations with B vitamins; three or more years of follow-up, an 8% reduction in risk, cereal) folate fortification, a 9% reduction in risk, with systolic blood pressure above 130 mm Hg, a 14% reduction in risk and with an antiplatelet agent use rate below 50%, a 16% reduction in risk.
Some trials that included chronic kidney disease patients reported decreased glomerular filtration rate with B vitamin supplementation.
Researchers conducted a detailed subgroup analysis for vitamin B12 but did not find a significant benefit regarding intervention dose of vitamin B12 or baseline blood B12 concentration.
In their conclusion the researchers write “B vitamin supplementation for homocysteine reduction significantly reduced stroke events, especially in subjects with certain characteristics who received appropriate intervention measures.”
This effect had a marginal significance in the absence of folate (vitamin B9) fortification of grain products but was not significant for populations already getting the vitamin in their food supply. Other factors associated with modest benefit included high blood pressure and low antiplatelet usage.
Dr. James F. Meschi. MD, chair of neurology at the Mayo Clinic in Jacksonville, Florida, related to MedPage Today "All three of these factors do not apply to the typical stroke-prone patient seen in the U.S. clinic.” "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.”
Dr. Ralph L. Sacco, MS, MD, FANN, FAHA. Adjunct Professor, Department of Neurology, Columbia University and Professor and Chairman, Department of Neurology, Miller School of Medicine, University of Miami, related to Medscape "When one examines the largest clinical trials individually, there is no significant effect of vitamin B supplementation for primary or secondary stroke prevention, so it's difficult to use a meta-analysis to change evidence-based guidelines. There may be some subgroups of patients who could benefit from vitamin B supplementation, but unfortunately the effects are small and limited."
This study is published in Neurology.