A study published in the journal Stroke (2005; 36(11): 2404–2409) examined whether higher-dose B-vitamin supplementation—particularly vitamin B12—might be linked with reduced risk of stroke. The study included 2,155 men and women with a mean age of 66 years.
Participants were assigned to receive either:
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a low-dose supplement containing 20 mcg folate, 200 mcg vitamin B6, and 6 mcg vitamin B12, or
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a high-dose supplement containing 2.5 mg folate, 25 mg vitamin B6, and 400 mcg vitamin B12
These nutrients were selected because they act as cofactors in homocysteine metabolism. Elevated homocysteine levels have been linked in observational studies with increased cardiovascular and cerebrovascular risk.
To reduce confounding, participants were pre-screened to exclude individuals with already elevated B12 levels or conditions that might impair nutrient absorption.
Over the course of the study, the group receiving the higher-dose B-vitamin supplement experienced a 21% lower risk of stroke compared with the low-dose group. No comparable reduction was reported for heart attack risk.
The authors concluded that vitamin B12—when included as part of a B-vitamin combination aimed at lowering homocysteine—may play a role in reducing stroke risk in certain populations, particularly among older adults with adequate absorption and without excess baseline levels.
