Vitamin B6, B12 and folic acid - are known to reduce the level of homocysteine in the blood. Elevated levels of Homocysteine are associated with an increased risk of stroke, cognitive impairment and Alzheimer's disease. A study of a group of elderly patients with mild cognitive impairment found that after two years of intervention with high doses of B6, B12 and folic acid there was significantly less brain shrinkage compared to a subset that was given placebo treatment.