Selenium: recent clinical advances.

Selenium is an essential trace element that serves a number of metabolic functions. Its recommended dietary allowance has been set at 55 µg per day for adults. Selenium deficiency has not been reported to occur in healthy persons in the United States and Canada. However, many people in the world have suboptimal intakes of the element and may suffer clinical consequences. Certain viruses become more virulent by being passed through selenium-deficient animals. This might have public health consequences because viruses of clinical significance infect selenium-deficient populations in China and elsewhere. Selenium has also been promoted as a cancer chemopreventive agent when given at supranutritional levels. Studies are underway to evaluate this use of the element.