Exercise performance, muscle damage and oxidative stress: a role for antioxidants?

A free radical is a molecule with an unpaired electron in its outer orbital and is produced during normal cellular metabolism. High levels of radicals can damage cells by reacting with cellular components (e.g., proteins and lipids). This form of damage is called oxidation and can result in a lethal injury to cells. Given that radicals are produced during normal metabolism, it is not surprising that cells contain antioxidants (molecules that eliminate radicals) to reduce the risk of radical-mediated injury. Two major classes of antioxidants work together to reduce the potentially harmful effects of radicals: 1) enzymatic antioxidants and 2) non-enzymatic antioxidants. Key antioxidant enzymes include superoxide dismutase, glutathione peroxidase, and catalase. These enzymes are manufactured in the cell and cannot be obtained through dietary supplementation. Important non-enzymatic antioxidants include vitamins E and C, and betacarotene. These antioxidants are included in many foods and can also be obtained through dietary supplements. Vitamin E and beta-carotene are lipid-soluble antioxidants and protect cell membranes from radical damage. Vitamin C is a water-soluble antioxidant and works in conjunction with vitamin E to protect both lipids and proteins in the cell from radical damage