Substances that inhibit oxidation in plant and animal cells. Culinarily, antioxidants help prevent food from becoming rancid or discolored. In the body, many scientists believe that antioxidants may contribute to reducing cancer and heart disease. Ascorbic acid (vitamin C), which is easily obtained from citrus fruits, is a well known natural antioxidant, as is vitamin E, which is plentiful in seeds and nuts. Antioxidants are also abundant in cruciferous vegetables such as broccoli and Brussels sprouts.