[How do antioxidants work?].

Reactive oxygen species, formed by incomplete reduction of molecular oxygen, may cause oxidative stress in the organism and be involved in the pathogenesis of many diseases. A number of anti-oxidants are necessary to counteract the harmful effects. Some antioxidants are enzymes which catalyze the breakdown of reactive oxygen species, some act by chelating transition metals, which makes them non-reactive, while chain-breaking antioxidants act by halting the cascade of free radical reactions. The effect of redox active antioxidants depends on their redox status. In some circumstances antioxidants can have pro-oxidant effects. The mechanisms may be reductive release of metals, accumulation of the oxidized form of redox active antioxidants, or merely an unfavourable equilibrium between various antioxidants. At present there is no basis for recommending the prophylactic use of commercially produced antioxidants. In particular, the optimal combinations of antioxidants are not yet known. If the aim is to improve the antioxidant defence of the body, our advice is still a mixed diet and regular physical activity.