Researchers from Beijing Geriatric Hospital, in a meta-analysis of 12 studies involving 47,523 patients with cardiovascular disease, found that those that supplemented with folic acid (vitamin B9) reduced their risk of stroke by 15 percent. Folic acid, which the study authors called a “safe and inexpensive therapy,” lowers levels of homocysteine, an amino acid linked to heart disease; research indicates that 0.5 to 5 milligrams daily can reduce homocysteine levels by approximately 25 percent.