Researchers said antioxidants may alleviate artery damage from oxygen free-radicals. In one study, researchers gave 70 people an antioxidant supplement containing 500 mg of vitamin C, 200 IU of vitamin E, 100 mcg of selenium, and 60 mg of CoQ10 per day, or a placebo. Participants had at least two factors that raised chances for heart disease, including high blood pressure or blood fats, diabetes, or they were smokers. After six months, while the placebo group had not improved, the antioxidant group had more flexible blood vessels, lower blood pressure, better blood sugar control, and an 18 percent increase in HDL, the good cholesterol.