[Antioxidant vitamins and disease--risk of a suboptimal supply]

Reactive oxygen species (ROS) such as the superoxide (O2.-) and the hydroxyl radical (OH.) are aggressive chemical compounds that can induce tissue injury, e.g. by peroxidation of polyunsaturated fatty acids in cell membranes or directly by DNA damage. Many pathological conditions are in part caused by ROS. There are various biological defense systems directed towards radicals: specific enzymes, e.g. superoxide dismutase or glutathione peroxidase; nonessential antioxidants, e.g. the plasma proteins and uric acid; and the essential antioxidants, e.g. vitamin C, vitamin E and carotenoids. This review focuses on various clinical conditions where ROS are of major pathogenetic significance: ageing, cancer, stroke, hematologic disorders, adult respiratory distress syndrome (ARDS) and organ preservation in transplantation medicine. Moreover, the complementary system of the vitamins C and E in defense against ROS is shortly discussed and the need for further studies about the effects of antioxidant treatment, such as interventional studies, proposed. The chronic exposure of the organism to ROS is an important factor for tissue injury in the process of ageing. Lipofuscin is a typical product of lipid peroxidation and inversely correlates with longevity of an organism. The ingestion of higher doses of antioxidative vitamins was recently shown to be protective for the development of cataracts, a degenerative disorder of the eye. The impairment of the immune system in elderly people might be prevented by a higher intake of multivitamin supplements. Whether supplementation with antioxidative vitamins can extend the life span in humans, as was shown in experimental animals, remains unanswered.(ABSTRACT TRUNCATED AT 250 WORDS)