Antioxidants are a group of chemical compounds that protect against free radicals.  Antioxidants slow or prevent oxygen from reacting with other compounds.  Examples include vitamins C and E, beta carotene, the minerals selenium and germanium, superoxide dismutase (SOD), coenzyme Q10, catalase, and some amino acids.

Free radicals are highly reactive molecules.  They are produced naturally or can be induced by exposure to things like radiation, certain chemical pollutants, or other sources.

When free radicals come in contact with healthy cell membranes, they can cause damage to the membrane and may cause the cell to die.  Antioxidants are often the substances that give foods their color and flavor.  Some antioxidants have been shown to have cancer-protecting potential because they neutralize these free radicals.