Another energy booster catching on among athletes—including cyclist Lance Armstrong—is quercetin, an antioxidant found in apples, onions, and berries. In addition to quelling inflammation and mopping up free radicals, “it gives you a very smooth energy lift,” says Rikki Keen, RD, who teaches sports nutrition at University of Alaska Anchorage. Men who took 1,000 mg quercetin daily for two weeks went 3 percent farther during treadmill time trials than those taking a placebo, in a 2010 study.

Dose: 650­–1,000 mg in two to three doses daily, one taken one hour before a workout. Take with vitamin C to enhance absorption.