Quercetin is an antioxidant found in apple skins, cranberries, blueberries, onions, tea, and red wine. It might be an effective supplement for active bodybuilders, because it prevents illness and improves cell aerobic capacity.

A study from Appalachian State University showed that supplementing quercetin for two weeks caused small increases in endurance performance, compared to a placebo. They noted a trend toward increased muscle cell mitochondria (the cell energy centers).

Other studies concluded that quercetin reduced inflammation, boosted the immune system, stimulated mental performance, protected the heart from coronary artery disease, and prevented protein breakdown. Quercetin supplements prevented colds, improved exercise performance and increased mitochondria. It also has caffeine-like effects, which might promote mental and physical performance. Quercetin supplements might prevent overtraining, strengthen the immune system, and improve general health. (Medicine Science Sports Exercise, 42: 338-345, 2010)