Vitamin B12 deficiency may increase the risk of stroke by increasing the levels of Homocysteine. High Homocysteine level may cause early artheriosclerotic changes within vessels’ wall (hardening of vessels). By lowering Homocysteine level with vitamin B supplementation (vitamin B12 and folic acid) one may be able to reduce the risk of stroke. Blood testing may be needed to check for both Homocysteine level as well as levels of vitamin B12 and folic acid. Research data from four randomized controlled trials (included around 55 thousand participants and investigators) measured the association between B vitamin supplementation and stroke events. For this group, reduction of overall stroke events resulting from the reduction of Homocysteine levels because of vitamin B supplementation was observed.