Acta Pharm. 54 (2004) 261-276
[ Full paper in PDF ]Selenium (the Greek goddess of moon) is a metalloid element with atomic number 34 and an average relative atomic mass of 78.96, melting-point at about 220.5 °C, boiling-point at about 684.9 °C. It belongs to the sulfur family of elements (which also includes sulfur, oxygen, tellurium and polonium), and has some common properties with sulfur, including valency and the ability to form covalent bonds with carbon (1, 2). Selenium was discovered in 1817 by the Swedish physician and chemist Jons Jakobs Berzelius (1779-1848). Marco Polo gave the first account of selenium toxicity, which he observed during his travels in western China in the 13th century. Until the 1950's selenium was considered to be toxic to humans, but in 1958 Schwarz and Foltz (3) described the relationship between selenium intake by food and prevention of liver necrosis in rats. Importance of selenium intake to humans was observed in the 1970's, when a cardiomyopathy endemic in certain areas of China was shown to be linked to dietary selenium deficiency. This disorder, known as Keshan disease, is endemic in the areas of China with some of the most selenium-poor soils in the world (4). Selenium is a trace element that is essential in small amounts but can be toxic in larger amounts. It is known today that humans and animals require selenium for the normal function of a number of selenium-dependent compounds. Selenium levels in the body are mainly dependent on the amount of selenium in the diet. Selenium is derived from both vegetable and animal products. The amount of selenium in food is a function of the selenium content of the soil. It enters the food chain incorporated into plant proteins as the amino acids L-selenocysteine and L-selenomethionine as well as some inorganic forms of selenium.
Keywords: selenium, metabolism, function, supplementation, toxicity