By: Thomas Pickering, MD, DPhil, FRCP, Director of Integrative and Behavioral Cardiology Program
of the Cardiovascular Institute at Mount Sinai School of Medicine, New York.

Folic acid is a vitamin not usually thought of in the context of vascular disease. One of the actions of folic acid is to promote the breakdown of homocysteine, which is probably a name that you are not familiar with, but one that you are sure to hear more about. It is pronounced 'homo-cyst-eh-een' and is an amino-acid which is normally present in the blood (amino-acids are the building blocks for proteins). It was shown many years ago that children with a rare genetic defect which resulted in abnormally high blood levels of homocysteine developed arterial disease at a very early age. Subsequently it was also found that adults with moderately high levels also had more severe arterial disease than people with normal levels. It is thought that homocysteine damages arteries, and that folic acid converts it into a substance which does not.

In this study, a population of more than 5,000 Canadians who had had their blood folic acid levels measured as part of a national nutrition survey conducted between 1970 and 1972, were contacted 15 years later to see who had developed heart disease. The principal finding was that people with the lowest folic acid levels were at a 70% higher risk of dying from a heart attack when compared with people with high folic acid levels.

Doctor’s comments

This study was started before anyone realized that homocysteine and folic acid are involved in the development of heart disease; the folic acid levels were measured as part of the nutrition survey. It provides strong evidence that low blood folic acid levels are likely to lead to heart disease. Folic acid is found in fruits and vegetables, and elevated homocysteine levels can be reduced by eating only moderate amounts of folic acid. It has been estimated that as many as 88% of Americans do not get enough folic acid in their diet, and there is currently a plan to fortify the folic acid content of some foods. Even so, this is unlikely on its own to be enough to keep down homocysteine levels. Thus, the main implication of this study is that maintaining a high intake of fruits, beans, and leafy vegetables such as spinach is another way of helping to avoid heart disease.

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