Heart study questions role of homocysteine

In the effort to predict vulnerability to heart disease and stroke, doctors have looked at cholesterol levels, blood pressure, obesity and, more recently, the amount of homocysteine in the blood.

But the significance of elevated levels of this amino acid may have been overstated -- at least in healthy people, according to a review of more than 30 studies involving 5,000 people.

In the review, published in the Oct. 23/30 issue of the Journal of the American Medical Assn., a group of scientists led by Dr. Robert Clarke of the Radcliffe Infirmary in Oxford, England, found elevated homocysteine levels to be at best only a modest predictor of a person’s risk for stroke and heart disease. The authors said that large studies of whether folic acid supplements can lower cardiac disease risk will provide more information about the relevance of high homocysteine.

When proteins are digested, the body produces homocysteine. A lot of homocysteine is believed to damage cells in the walls of blood vessels, thus contributing to the formation of the artery-clogging plaques linked to strokes and heart attacks. Folic acid, also known as folate, is a B vitamin that helps break down homocysteine in the body.

In the meantime, homocysteine may be a more meaningful risk factor in patients with a genetic mutation that lowers folate levels and raises homocysteine levels, according to a Dutch review of 40 studies involving nearly 24,000 people.

That review, in the same issue of the journal, found that patients with the mutation were at increased risk of coronary heart disease. The authors suggested that increasing folate in the diet, which has occurred in the U.S. with the fortification of flour and other foods, could decrease risk.