"Antioxidant" is a classification of several organic substances, including vitamins C and E, vitamin A (which is converted from beta-carotene), selenium (a mineral), and a group known as the carotenoids. Carotenoids, of which beta- carotene is the most popular, are a pigment that adds color to many fruits and vegetables -- without them, carrots wouldn't be orange, for example. Together as antioxidants, these substances are thought to be effective in helping to prevent cancer, heart disease, and stroke.
At the molecular and cellular levels, antioxidants serve to deactivate certain particles called free radicals. In humans, free radicals usually come in the form of O2, the oxygen molecule. The oxygen molecule wants to be oxidized (remember that stuff from your chemistry class?), and this oxidation process can sometimes be carcinogenic. Free radicals are the natural by-products of many processes within and among cells. They are also created by exposure to various environmental factors, tobacco smoke and radiation, for instance.
Antioxidants play the housekeeper's role, "mopping up" free radicals before they get a chance to do harm in your body. Researchers have postulated that antioxidants prevent the possible carcinogenic effects of oxidation. Despite numerous studies carried out on the role of antioxidants in cancer and heart disease prevention, the jury is still out as to which groups of people, if any, benefit from taking antioxidant supplements.
Conflicting reports on the health benefits of antioxidants and beta-carotene exist. It is difficult to know what to believe and whose advice to follow. It is best to remember that vitamin and mineral supplements should never be used as substitutes for a healthy, well balanced diet! It is also important to note that we can "over- supplement" our bodies, taking much more than the recommended daily value of certain vitamins and minerals. Vitamins A and E are fat soluble, meaning that excess amounts are stored in the liver and fatty tissues, instead of being quickly excreted, creating a risk of toxicity. Your best bet is to eat a diet rich in fruits, veggies, and whole grains. Sweet potatoes, carrots, spinach, cantaloupe, and mangoes are great sources of antioxidants.