Substances that protect against free radicals, molecules occurring naturally in the body that can damage healthy cells.
Some antioxidants are found naturally in the body, whereas others must be consumed in food. Some of the more commonly known dietary antioxidants include vitamin C, vitamin E, and carotenoids, such as beta-carotene and lycopene. Vitamin C is found abundantly in fruits and vegetables. Vitamin E can be found in nuts, seeds, and vegetable oils. Carotenoids are colored antioxidants that give fruits and vegetables their color. For example, beta-carotene gives carrots their orange color, and lycopene provides the red color to tomatoes.
Free radicals have been implicated in a number of diseases, including heart disease, cancer, diabetes, osteoarthritis, and a number of inflammatory diseases such as rheumatoid arthritis. Antioxidants are thought to provide protection against these diseases. Many people take vitamin supplements in the hopes of staving off disease, but in a number of large studies, antioxidants in the form of supplements have not been shown to offer protection. (The one exception appears to be age-related macular degeneration, or breakdown of the light-sensitive cells in the center of the retina, for which vitamin supplements appear to slow the progression.) Nutrition experts say that the best source of antioxidants is a diet rich in fruits and vegetables, which provides a number of other important health benefits.