Supplement: Antioxidants, Including Vitamins A, C, and E
Conventional Wisdom: They destroy free radicals, molecules created during exercise that are thought to contribute to cell damage.
Science Says: According to recent studies, some free radicals appear to trigger chemical reactions that actually help strengthen muscles after exercise and improve health. So taking antioxidants in excess may curb the benefits of exercise.
Conventional Wisdom: A flavonoid found naturally in apples, red wine grapes, and other fruits and vegetables, it’s thought to improve endurance capacity and fight fatigue.
Science Says: Athletes get little or no benefit from it. An upcoming review of seven studies concluded that quercetin may be useful for out-of-shape people who start exercising but does next to nothing for the already fit.
Conventional Wisdom: It’s the most popular supplement in the country, and power athletes insist it helps build muscle strength and bulk.
Science Says: It does—to a point. College football players who used creatine bench-pressed more weight, and Australian soccer players sprinted faster. But if you’re an endurance athlete, creatine draws extra water into cells, leading to diarrhea and even cramping.
Conventional Wisdom: DHEA raises testosterone levels and helps build muscle and increase power.
Science Says: Yes and no. DHEA is a naturally occurring hormone that affects the body’s ability to produce testosterone. But a 2006 study in the New England Journal of Medicine found that daily doses in men with normal levels did not increase muscle strength.