The controversy surrounding selenium and cardiovascular disease: a review of the evidence.

Selenium is an essential trace element that is an integral part of many proteins, with catalytic and structural functions. The antioxidant properties of some selenoproteins, such as glutathione peroxidase, may be particularly important in carcinogenesis and heart disease. The content of selenium in food depends on the selenium content of the soil where the plants are grown or the animals are raised. Moreover, the metabolism of selenium is determined by its dietary form: some forms are better utilized than others. Therefore, wide variations have been found in selenium status in different parts of the world. In animal studies, selenium deficiency is associated with cardiomyopathy and sudden death, as well as reduced T-cell counts and impaired lymphocyte proliferation and responsiveness. Abnormalities in liver function, brain, heart, striated muscle, pancreas and genital tract have also been reported. In humans, selenium deficiency has been implicated in the etiology of cardiovascular disease and other conditions in which oxidative stress and inflammation are prominent features, but there is still only limited evidence from epidemiological and ecological studies for this, and the therapeutic benefit of selenium administration in the prevention and treatment of cardiovascular diseases remains insufficiently documented. Interventions studies are currently in progress to assess the benefits of selenium supplements in primary and secondary prevention of atherosclerosis. The results to date are inconclusive and further controlled trials are needed.