Antioxidant vitamin supplements: update of their potential benefits and possible risks.

Oxidative damage to biological structures has been implicated in the pathophysiology of cardiovascular disease and cancer, the 2 most common causes of death in developed countries. This has stimulated interest in the possible role of natural antioxidant vitamins in preventing the development of these diseases. Epidemiological studies have offered support for the notion that high blood concentrations or dietary intake of antioxidant vitamins may have a protective effect. On the basis of these findings and powerful marketing strategies, many healthy members of the population are now voluntarily consuming antioxidant supplements. A number of long term, prospective, randomised, placebo-controlled trials examining the protective effect of antioxidant supplements have now been completed. Their results have been generally disappointing and have provided little evidence of efficacy. Of greater concern, they have unexpectedly raised concerns that antioxidants, notably betacarotene, might increase the rate of development of cancers in high risk individuals. For this reason regular consumption of antioxidant vitamins supplements cannot yet be advocated as a healthy lifestyle trait.