Cardiovascular disease is one of the most significant disease burdens today. In addition to traditional risk factors, elevated homocysteine (hereafter referred to as Hcy) levels are receiving increasing attention as an important independent risk factor for the development of cardiovascular diseases. Studies related to hypofolateemia, which is closely associated with high Hcy, and folic acid supplementation for the prevention of cardiovascular diseases are also attracting attention. The nutritional role of folic acid in humans has been confirmed since 1948, and deficiency of folic acid can cause megaloblastic anemia. Folic acid supplementation has been used to treat nutritional megaloblastic anemia and to prevent fetal neural tube abnormalities in pregnant women. In recent years, the role of folic acid in the prevention and treatment of cardiovascular diseases has received increasing attention. Although the current findings do not confirm the role of folic acid in the prevention and treatment of coronary heart disease, and some studies even suggest that it may be harmful, the role of folic acid in the prevention and treatment of cerebrovascular disease is increasingly recognized by the academic community. the Norwegian Vitamin Study (NORVIT), published in 2005, found that high doses of vitamin B, including folic acid vitamin B did not prevent cardiovascular disease in patients with myocardial infarction and may even put them at increased risk of cardiovascular disease. But the NORVIT study focused on cardiovascular disease and not enough on stroke. The HOPE2 study published last year was a study of 2.5 mg of folic acid, 50 mg of vitamin B6 and 1 mg of vitamin B12 daily supplementation versus placebo control in 5522 people over 55 years of age with previous coronary heart disease, cerebrovascular disease, peripheral vascular disease or diabetes, with a mean follow-up of 5 years. Although the above B-vitamin complex was not shown to reduce the combined endpoint of cardiovascular death, myocardial infarction, and stroke, subgroup analysis reduced the risk of stroke by 25%. Similar to the results of the HOPE2 study, a meta-analysis published in this year’s Lancet, in which we participated, also confirmed that folic acid supplementation is effective in reducing the risk of stroke in humans, with a more pronounced effect in primary stroke prevention. This analysis involved eight large international clinical trials on the efficacy of folic acid supplementation for stroke prevention in 16,841 subjects from 1996 to 2006. These studies compared the effect of folic acid in combination with other B vitamins (B6 and B12) or alone with placebo or common lifestyle interventions on endpoint events. The studies lasted at least 6 months, with stroke as one of the endpoint events. The countries involved were mainly developed countries in Europe and the United States, including the United States, Canada, 3 European countries, Australia, New Zealand, and one study conducted in China. The population was predominantly middle-aged and elderly and included both men and women, with slightly more men. Folic acid dosage in the intervention group ranged from 0.5 to 15 mg/d. One of the eight studies was conducted in a population with previous stroke, and the others in a population with coronary heart disease, end-stage renal disease, and esophageal atypical hyperplasia. Folic acid was added to food in some of the intervention areas. Results showed that folic acid supplementation (alone or in combination with other group B vitamins) reduced the risk of stroke by 18% (p=0.045). Subgroup analysis showed a 25% (p=0.003) reduction in the risk of stroke in those who did not add folic acid to their food, a 25% (p=0.003) reduction in the risk of stroke in those with no previous stroke, and a 23% (p=0.012) reduction in the risk of stroke in those with a ≥20% reduction in serum Hcy. The trend analysis also suggested that the relative risk of stroke decreased further with longer duration of folic acid supplementation and greater decrease in Hcy. In fact, folic acid supplementation works by reducing Hcy in the body. The “Dietary Nutrient Reference Intakes for Chinese Residents” published by the Chinese Nutrition Society in 2001 suggests a daily intake of 0.4 mg of folic acid for adults over 18 years of age, including middle-aged and elderly people over 50 years of age, and 0.6 mg for pregnant women. The U.S. Centers for Disease Control has recommended 0.4 mg of folic acid daily for women of childbearing age and 0.8 mg for pregnant women. Women who have had multiple births or have chronic hemolytic anemia need an additional 0.2-0.4 mg of folic acid per day. The U.S. FDA has mandated that all cereal flours be fortified with 0.14 mg of folic acid per 100 g of flour since 1998, and Canada has begun to have a similar policy. The average daily intake of folic acid per person in Beijing is reported to be 0.25-0.28 mg, so there is a certain degree of inadequate folic acid intake in the country. The results of the above study give important insights into stroke prevention and treatment in China. Currently, the incidence of hypertension and stroke in China is high and on the rise, while hyper-Hcythemia is not uncommon in China. In particular, the expected effect of folic acid supplementation on stroke prevention should be better than that in western countries because of the high incidence of hypertension and stroke, low folic acid levels and high Hcy levels in the northern population of China. The only one of the meta-analyses mentioned above, the Chinese Linxian Nutrition Intervention Study, also showed a 37% reduction in the risk of stroke in this population after 2 years of folic acid supplementation at a certain dose. Thus, although the role of folic acid in the prevention of coronary heart disease is controversial, more and more studies are proving that folic acid plays an important role in the prevention of cerebrovascular disease, especially in primary prevention. It is believed that as scientific research progresses, clinical studies with cerebrovascular disease as the primary endpoint will further examine the role of folic acid in the prevention and treatment of this disease.