Antioxidant

Antioxidants are compounds that inhibit oxidation, a chemical reaction that can produce free radicals and chain reactions that may damage the cells of organisms. Antioxidants such as thiols or ascorbic acid (vitamin C) may act to inhibit these reactions. To balance oxidative stress, plants and animals maintain complex systems of overlapping antioxidants, such as glutathione.

Although certain levels of antioxidant vitamins in the diet are required for good health, there is still considerable debate on whether antioxidant-rich foods or supplements have anti-disease activity. Moreover, if they are actually beneficial, it is unknown which antioxidants are health-promoting in the diet and in what amounts beyond typical dietary intake. Some authors dispute the hypothesis that antioxidant vitamins could prevent chronic diseases, and some declare that the hypothesis is unproven and misguided. Polyphenols, which have antioxidant properties in vitro, have unknown antioxidant activity in vivo due to extensive metabolism following digestion and little clinical evidence of efficacy.