According to researchers, supplementing the diet with antioxidant vitamins and minerals appears to blunt the beneficial effects of certain cholesterol-lowering drugs.
Their findings suggest that patients with coronary artery disease who are taking simvastatin and niacin should steer clear of supplements containing vitamins E and C, beta-carotene or selenium.
Patients who took a "cocktail" of these four antioxidants along with simvastatin and niacin had smaller increases in HDL ("good") cholesterol levels over a 1-year period, compared with patients who took the medications alone, the investigators found. Simvastatin and niacin have been shown to reduce total cholesterol and LDL ("bad") cholesterol while boosting levels of HDL, which helps cut the risk of heart disease.
However, the findings do not suggest that patients avoid fruits and vegetables, which are naturally rich in antioxidants and contain a number of other compounds that may protect against heart disease, Dr. Marian C. Cheung, the study's lead author, told Reuters Health.
"Our findings are based on antioxidant supplements and not foods that are naturally rich in antioxidants. Therefore, coronary artery disease patients should continue to eat a variety of foods daily from all the basic food groups including fruits and vegetables," said Cheung, a researcher at the University of Washington in Seattle.
The study is published in the August issue of Arteriosclerosis, Thrombosis and Vascular Biology: Journal of the American Heart Association. It included 153 patients with heart disease and low HDL, aged 33 to 74. Patients were divided into four treatment groups: therapy with simvastatin and niacin; four antioxidant vitamin supplements; drug therapy plus antioxidants; or an inactive placebo.
After one year, patients on simvastatin and niacin alone saw their HDL increase by an average of 25 per cent, while HDL levels rose by an average of 18 per cent among patients on the medications plus antioxidants.
In addition, the HDL component responsible for most of its protective effects increased by an average of 42 per cent with medication, but remained unchanged among patients who added the antioxidant cocktail. This response was seen among all individuals, including diabetics and nondiabetics, smokers and nonsmokers, and those with normal or high blood pressure.
Patients who took only antioxidants or the placebo experienced no significant changes in HDL levels.
Exactly why antioxidant therapy blunted the beneficial effects of cholesterol treatment is not clear, and future studies should try to answer this question, said Dr. Lewis H. Kuller, an epidemiologist with the University of Pittsburgh in Pennsylvania.
For now, the current findings seem to reinforce a growing body of research demonstrating that supplementing the diet with certain antioxidants such as vitamin E and beta-carotene have no significant effect on heart disease in humans. Taken together, these results argue against recommending antioxidant vitamins to prevent or treat heart disease, according to Kuller.