Reactive oxygen species (ROS) generation has an important implication in the etiology of many diseases and in aging. Furthermore, strenuous physical exercise has been shown to increase oxidative stress to skeletal muscle and myocardium due to increased ROS generation. In order to optimize exercise benefits in the elderly whereas to prevent oxidative damage, we seek novel antioxidant protection, via dietary supplementation of phytochemicals in vegetables, fruits, grains, herbs and other natural sources. In one of our recent study, chronic dietary supplementation of North American ginseng (Panax Quinquefolium) was found to decrease ROS generation measured by dichlorofluorescin in several tissues of young and aged rats and attenuated age-related protein oxidative measured by reactive carbonyl derivatives. These changes were partially explained by the increases in endogenous antioxidant enzyme superoxide dismutase (SOD) and glutathione peroxidase (GPX) activities due to ginseng supplementation. In another study, we showed that dietary supplementation of a novel synthetic oat antioxidant, avenathramides, for 50 days in rats attenuated exercise-induced increase in ROS production in muscle and lipid peroxidation in the heart, while increasing SOD and GPX activities in these tissues. These studies are among a wide branch of literature showing the potential of dietary phytochemical antioxidant supplement to counteract oxidative stress due to aging and heavy exercise. However, many controversies still exist. Future studies should explore cellular and molecular mechanisms underlying the demonstrated antioxidant effects, their protection against specific pathophysiological conditions including aging, as well as novel ways to incorporate them into food and beverage.