Antioxidants in cardiovascular disease: randomized trials

Abstract

The hypothesis that antioxidant vitamins might reduce cardiovascular disease risk is based on a large body of both basic and human epidemiologic research. One of the most consistent findings in dietary research is that those who consume higher amounts of fruits and vegetables have lower rates of heart disease and stroke as well as cancer. Recent attention has focused on the antioxidant content of fruits and vegetables as a possible explanation for the apparent protective effects. Basic research provides a plausible mechanism by which antioxidants might reduce the risk of atherosclerosis. A large number of descriptive, case-control and cohort studies provide data suggesting that consumption of antioxidant vitamins is associated with reduced risks of cardiovascular disease. These data raise the question of a possible role of antioxidants, such as vitamins C and E, and beta carotene, in the primary prevention of cardiovascular disease but do not provide a definitive answer. Results from several large-scale randomized trials of antioxidant supplements are now available; however, results are not entirely consistent. The results of the major trials do not prove or disprove the value of antioxidant vitamins, nor do they incriminate them as harmful. They do, however, raise the possibility that some of the benefits from observational epidemiology may have been overestimated and that there may be some adverse effects. At this point randomized trial data are not yet sufficient to fully assess the risk-to-benefit ratios for antioxidant supplements. More reliable data should be forthcoming in the near future which will better define the role of antioxidants in the primary and secondary prevention of atherosclerotic disease as well as cancer.