[Nutritional importance of selenium].

Selenium is an important trace element that was considered toxic for humans and animals for a long time. The best known biochemical role of selenium is, as a selenocysteine residue, to be a part of the active site of the enzyme glutathione peroxidase (GSH-Px). The highest values of selenium have been found in protein foods (meat and fish); although selenium from vegetables sources are more available than from the other foods. Nowadays are not known exactly the recommended dietary allowances for humans, mainly for children. The selenium intake in Spain is 221 micrograms/person/day and the plasmatic values of Spanish people (87 +/- 14 micrograms/L) are within the European average (85 micrograms/L).