High levels of homocysteine in blood is one of the causes of cardiovascular disease.
David Wald, of the Wolfson Institute for Preventive Medicine, Barts and the London, Queen Mary School of Medicine and Dentistry told Reuters news: "The evidence is very persuasive that lowering homocysteine with folic acid will lower your risk of heart attack and stroke by about 10-20 percent."
Wald and his colleagues examined evidence from previous studies and found that tests involving large numbers of otherwise healthy people and people genetically prone to higher homocysteine levels yielded similar results - that folic acid had a protective effect.
Researchers think that higher homocysteine level in blood is increases the risk of cardiovascular disease by damaging the inner lining of arteries.
"The evidence shows clearly that those people who have the genetic defect who have higher homocysteine levels have a high risk," Wald said. "The work we have done looks closely at this type of evidence because if you take enough folic acid, or folate, you can cancel out the effect of this mutation".
Wald said that although the studies of the effects of lowering homocysteine levels were too small to be conclusive, the results were still consistent with the protective effect of folic acid.
"All the evidence put together is compelling," he said, adding that folic acid is a cheap and simple way to reduce heart disease and strokes.
Cardiovascular disease is a leading cause of death worldwide.
