[Mineral substance in human nutrition. Selenium: absorption and bioavailability].

In the review there are discussed results of selenium absorption studies in human and animals gastrointestinal tract. According to plenty of experimental data selenate-anion is rapidly and quantitatively absorbed upstream concentration gradient the site of absorption being predominantly ileum. This process is Na+ and energy dependent. On the contrary seleniteanion is absorbed mostly in jejunum, the rate of uptake is less than for selenate in model systems and absorption does not occur toward concentration gradient. Under physiological conditions the most part of selenite is transported as mixed thiols with glutathione and some other tissue thiol compounds. Selenium amino acids are transported by corresponding transfer systems with specificity for analogous sulfur containing amino acids. Whereas bioavailability of transition al metals salts rarely exceeds 10-20%, selenium food sources (both organic and inorganic origin) are typically high absorbable predominantly on 60% or more and in some cases almost on 100%. From this point of view selenium food sources bioavailability evaluation must take into account their metabolic retention and toxicity indicies rather than absorption ratio (such is for zinc, chromium and other metal ions).