Antioxidants are naturally occurring substances that prevent damage to cells, membranes or organs by blocking free radicals and reactive oxygen-containing molecules. These oxygen-compounds are unstable and ‘looking’ for extra electrons: in doing so they injure DNA and cells, such as causing a cut apple to turn brown, accelerating human aging, and contributing to heart disease and cancer. Antioxidants can lend an electron to 'calm' the free radical and prevent tissue damage. Most antioxidants are best taken with food, e.g. CoQ10 is fat-soluble and much better absorbed along with oil or fats in a meal.