If you've ever made a fruit salad, you probably know that squeezing lemon juice onto the apples, pears, and bananas will keep the fruit from turning brown. This brown color happens because of a process called oxidation—a reaction between the oxygen molecules in the air and the molecules in the substance the air meets.
A similar type of reaction happens inside your body all the time. Substances called oxidants, or free radicals, react with your cells, harming healthy tissue, weakening immunological functioning, speeding up the aging process, and contributing to chronic degenerative diseases. These free radicals are formed through normal body processes, as well as through environmental exposure to the sun, pollution, cigarette smoke, too much stress, and the intake of alcoholic beverages and unhealthy food. Antioxidants are substances that work like that lemon juice on the fruit, protecting healthy tissue by destroying free radicals before they do any damage. Antioxidants are believed to play a role in helping to fight and prevent cancer, heart disease, Alzheimer's disease, and other chronic conditions.