A lack of folic acid has been identified as a major cause of heart disease, along with smoking, diabetes, hypertension (high blood pressure) and cholesterol.

Researchers from Health Canada in Ottawa have made a direct link between an increased risk of fatal heart disease and low levels of folate in the blood.

Their findings tie in with earlier discoveries that high levels of the amino acid homocysteine can cause cardiovascular disease, which affects the heart and blood vessels. Homocysteine levels can be lowered with even a small amount of folate.

Most people have too low levels of folate, which can be found in fruit and vegetables.

In a separate commentary, Drs Meir Stampfer and Eric Rimm from the Harvard School of Public Health say the Canadian research is "an important advance" but it does not prove conclusively that higher folate intake, either through food or supplements, will reduce the level of cardiovascular disease. More research needs to be carried out, and urgently, they say.

The Canadian researchers studied the records of 5,056 men and women, aged between 39 and 79, and found that the 165 who died from heart disease had the lowest levels of folate in their blood.

!AJAMA, June 26, 1996.