Selenium bioavailability as selenite (74Se) and as a selenium drug (76Se) by stable isotope methodology.

Many forms of selenium supplement are commercialized. The purpose of this work was to study the bioavailability of one selenium drug, "Granions de Sélénium", as compared with sodium selenite. Each product was labelled with enriched stable isotopes, and by means of gas chromatography/mass spectrometry (GC/MS), the metabolism of the two forms was followed simultaneously. In a first study, the absorption of a single dose of 480 micrograms Se (Na-Selenite) containing 100 micrograms of 74Se was compared with that of 480 micrograms Se (Granions) containing 100 micrograms of 76Se. Measurement precision was mediocre and only apparent absorption, urinary excretion and body retention could be measured. In a second experiment, kinetic studies were performed after a single oral dose of 100 micrograms of 74Se (Na-selenite) and 100 micrograms of 76Se (Granions). Blood, urine and feces samples were collected for a week to determine the true absorption, plasma half-life, and turnover of these two compounds. No significant difference in the metabolism of selenium was observed between "Granions de Sélénium" and selenite. Both present two maximal absorption peaks at 6 h and 12 h and a bioavailability of 76%.