Taking antioxidant vitamin supplements - which millions of Americans do - can wipe out the major benefits of cholesterol-lowering medications, according to a new study from the University of Washington.

Compared to treatment with drugs alone, the combination of antioxidant vitamin supplements and cholesterol-lowering drugs resulted in a smaller increase in HDL cholesterol (the "good" cholesterol).

Investigators studied 153 patients with coronary artery disease and low HDL levels for a year. They were randomly assigned to one of four treatment groups: drug therapy with simvastatin and niacin; a vitamin supplement cocktail containing the antioxidants vitamins E and C, beta-carotene, and selenium; drug therapy plus the antioxidant supplements; or a placebo. The findings:

• Patients receiving drug therapy alone increased their HDL by 25%.
• Patients receiving drug therapy plus the antioxidants increased their HDL by 18%.
• Levels of HDL-2 (the component responsible for most of the risk-reducing benefits of HDL) increased by 42% in the patients on drug therapy alone.
• HDL-2 levels in patients taking the drugs plus supplements were unchanged.
• Antioxidant supplements alone had no effect on HDL or other cholesterol levels.

One of the study's investigators commented that the antioxidant supplements have no value on their own, and, "when combined with lipid drug therapy, it looks like the vitamins actually interfere with the lipid therapy’s ability to raise HDL cholesterol."

He advised doctors to tell their patients that using antioxidant supplements may be hazardous, especially in combination with lipid-lowering drugs. The research was reported in the August issue of the AHA journal Atherosclerosis, Thrombosis and Vascular Biology.

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