Abstract
Selenium is an essential trace element and 25 selenoproteins, which contain the element in the form of selenocysteine, have been characterized in mammals. Selenium exerts its biological activity largely through these selenoproteins. However, some selenium compounds, such as selenite, Se-methylselenocysteine, methylseleninic acid, and selenomethionine, also have biological effects. Several studies indicate that these selenium compounds are among the most promising agents for cancer chemoprevention and anti-aging. A large chemoprevention study has been carried out using selenomethionine, because selenomethionine was thought to be an appropriate form of selenium supplementation for human nutritional. However, a randomized controlled trial shows that selenium-rich yeast (containing selenomethionine) may increase the risk for type-2 diabetes. The study of the chronic effects of selenium compounds including selenomethionine for usage in long-term supplementation is needed.
