Experts are investigating the relationship between homocysteine and coronary artery disease (CAD). Homocysteine is a naturally occurring amino acid in the body; some people are slow to metabolize it, so that it builds up in the bloodstream. High levels of this substance are found in about one-third of patients who have CAD or who have had a stroke. Thus it has been identified as a risk factor for CAD, but scientists have not yet shown that it is an actual cause.

A number of research studies are investigating whether high levels of homocysteine damage the endothelial lining of the arteries. A new study from the Wales Heart Institute has reported that folic acid improves the lining of the arteries (endothelium) before it affects the levels of homocysteine. Many doctors advise patients to take folic acid supplements, since folic acid safely and economically reduces homocysteine levels.

Researchers studied endothelial function by measuring blood flow and dilation of the arteries. They studied the effects of folic acid in 33 patients with CAD who took the supplement for six weeks. They found that endothelial functioning improved immediately - within two hours of taking the first dose of folic acid and before there was any reduction in the homocysteine level.

They concluded that folic acid improves endothelial function in people with CAD in a way that is not related to homocysteine. Thus, while doctors may prescribe folic acid to reduce homocysteine levels, its benefits are broader in improving arterial function.

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Source:  Doshi SN, McDowell IFW, Moat SJ, et al. Folic acid improves endothelial function in coronary artery disease via mechanisms largely independent of homocysteine lowering. Circulation, January 2002;105:22. (Abs.)