Interventional Trials of Antioxidants

Abstract

Prospective observational studies have found consistent associations between higher intakes of fruit and vegetables and reduced rates of coronary heart disease (CHD) and ischemic stroke. The exact mechanisms for these apparent protective effects are not entirely clear. It is possible that higher fruit and vegetable intake replaces fat and cholesterol intake, but alternatively, the observed beneficial effects may be due to micronutrients contained in the fruits and vegetables. Micronutrients with antioxidant properties might be responsible for the lower rates of cardiovascular disease (CVD) associated with fruit and vegetable consumption. Laboratory research has identified a possible mechanism – the inhibition of oxidative damage – by which antioxidants might reduce the risk of atherosclerosis and CVD. In addition, many cross-sectional, case-control, and cohort studies have found an association between antioxidant vitamin consumption and a reduced risk of CVD. These results suggest that antioxidants such as vitamin E, beta-carotene, and vitamin C may be involved in the prevention of CVD but do not provide a definitive answer. Several large-scale, randomized trials of antioxidant supplements have now been completed and are not entirely consistent. In this chapter, we discuss the rationale for conducting large-scale trials of antioxidant supplements and review completed and ongoing trials.