Thursday July 31 6:33 PM EDT

By E. J. Mundell

Researchers say antioxidant compounds, such as vitamin C, E, and beta-carotene may slow down the oxidation of 'bad' LDL cholesterol, a process which contributes to heart disease.

A study led by investigators from the University of Michigan Preventive Cardiology Program in Ann Arbor, Michigan, concludes that there is "a role of antioxidants in secondary prevention (of coronary artery disease)."

The researchers report their findings in the current issue of the Journal of the American College of Cardiology.

Antioxidants have gained popularity in recent years due to claims that they help lower levels of 'bad' cholesterol, reduce the buildup of fatty plaques on artery walls, and preserve the function of the cells that line arteries. All of these effects can help counter the arterial deterioration that characterizes coronary artery disease.

To test the efficacy of antioxidants in fighting cholesterol, the Michigan researchers placed 45 patients, all with diagnosed cardiovascular disease, on three types of diets for a period of three months. Some of the study participants were given a 'mid-dose' daily regimen of antioxidants, which included 400 international units (IU) of vitamin E, 500 milligrams (mg) of vitamin C, and 12 mg of beta-carotene. Another group received 'high-dose' supplementation, double the amount of antioxidants dispensed daily to the 'mid-dose' group. A third group received placebo only -- this group served as a comparison group for the other two.

The researchers measured blood-levels of antioxidants throughout the study. They also looked at a time-specific, chemically determined measurement of LDL cholesterol oxidation known as "lag phase." The slower the lag phase, the greater the resistance of LDL to oxidation -- and the lower the risk of LDL causing arterial disease. The researchers call lag phase evaluation "the most appropriate measure of the effect of antioxidant vitamin supplementation on LDL oxidation."

The results? Investigators discovered that those patients on the 'high-dose' antioxidant regimen saw "a significant reduction" in LDL cholesterol oxidation during the 12 weeks of the study. In fact, they noted "a doubling of mean (LDL oxidation) lag phase" in the high-dose group.

Even those heart patients taking the 'mid-dose' regimen displayed slower LDL oxidation rates compared with those patients placed on placebo, the researchers say.

They add that their results back up the findings of previous studies, and point to a positive role for antioxidant supplementation among those suffering from coronary artery disease.

The researchers do caution that the possible long-term side effects of high-dose supplementation with vitamins C, E, and beta-carotene remain unknown. "The potential adverse effects of high dose vitamin supplementation deserves further investigation," they conclude.

SOURCE: Journal of the American College of Cardiology (1997;30(2):392-397)