The Essential Trace Element Selenium: Requirements for Selenium Intake in Health and Disease

Selenium is an essential trace element and micronutrient for humans that exerts most of its biological actions through selenoproteins, which have the rare amino acid selenocysteine in their active centre. Several selenoproteins such as glutathione peroxidases (GPx) and thioredoxin reductases (TrxR) have antioxidant and redox-active functions. Assumed (and in part controversially discussed) beneficial effects of selenium on human health include the prevention of some types of cancer, slower progression of autoimmune thyroid diseases, adjuvant therapy of viral infections and support of immune, reproductive and cognitive functions. In the diet, selenium is mainly present in form of the amino acids selenomethionine and selenocysteine, while dietary supplements may also contain higher amounts of inorganic selenium compounds such as sodium selenite and selenate. Recently, the European Food Safety Authority (EFSA) has set the dietary reference value for adequate selenium intake of adults to 70 mu g/day, as did the German Society for Nutrition (DGE) with 60 mu g/day for women and 70 mu g/day for men. These values are based on the requirements to saturate blood levels of the selenium transport protein selenoprotein P (SePP1). Many Europeans including Germans -ingest less selenium; however, selenium deficiency is not a general problem. On the other hand, selenium supplementation beyond the doses required for SePP1 optimisation may not provide additional health benefits and, according to some studies, may even provoke adverse side effects. Therefore, dietary selenium supplementation is not recommended for healthy people in general. Persons who wish to take selenium-containing dietary supplements should have measured their plasma/serum selenium or SePP1 levels first. Selenium supplementation might be useful for persons with low selenium status and/or increased needs of selenium.