Bioavailability, selenomethionine

Yoshida M, Tashiro H, Iwami K, et al. 1983. Bioavailability of selenite, selenomethionine and selenocystine in rats with silver loading. Agric Biol Chem 47 807-813. 

Cases, J., Vacchina, V., Napolitano, A., Caporiccio, B., Besancon, P., Lobinski, R., and Rouanet, J.-M. 2001. Selenium from selenium-rich spirulina is less bioavailable than from sodium selenite and selenomethionine in selenium-deficient rats. J. Nutr. 131(9), 2343-2350. 

Elemental selenium (selenium[0]) is rarely found naturally, but it is stable in soils. Selenates (selenium[+6]) and selenites (selenium[+4]) are water soluble and can be found in water. Sodium selenate is among the most mobile forms of selenium because of its high solubility and inability to adsorb to soil particles. More insoluble forms, such as elemental selenium, are less mobile therefore, there is less risk for exposure. Because of greater bioavailability, water-soluble selenium compounds are probably more lethal than elemental selenium by any route. Selenium is found in nature complexed with multiple compounds, and although various forms are discussed in the profile, many others exist. Plants can contain organic selenium in the form of the amino acids selenomethionine and selenocysteine, along with the dimethyl selenides. Elemental selenium can be oxidized to form selenium dioxide. While the products of oxidation might be expected at the soil surface, elemental selenium would be the expected predominant form in deep soils where anaerobic conditions exist. Selenium sulfides, used in some antidandruff shampoos, are not very water soluble and, therefore, like elemental selenium are relatively immobile in the environment. 

RNSRUD R and Lorentzen M (2002) Bioavailability of selenium from raw or cured selenomethionine-enriched fillets of Atlantic salmon (Salmo solar) assessed in selenium deficient rats. 

Differences in the selenium content of foodstuffs are due in part to geographical differences in the amounts of the element that are transferred from soil to the food chain. Selenium-deficiency diseases related to selenium-poor soil are recognized in parts of China and elsewhere, but soils rich in selenium (above 5 ppm) are found in parts of the United States. The selenium in most plant-derived foods, present substantially as selenomethionine (SeMet) and selenocysteine (SeCys) derivatives, has reasonably good bioavailability. However, in animal-derived foods selenium has a wide range of bioavailability as assessed by its ability to increase liver concentrations and glutathione peroxidase activity. 

Studies on Se bioavailability are important, as the metabolic fate and physiological function of dietary selenite may differ from that of selenomethionine or food selenium [20]. The Se content of whole blood, but not plasma, was significantly higher in sheep fed on high-Se wheat where the... 

Yeasts are capable of assimilating large quantities of the trace element selenium, mostly in a form of selenomethionine, which is easily bioavailable for humans (Rayman 2004). As a safer selenium source compared to inorganic forms, selenium-enriched yeasts were used to manufacture supplements. But currently, selenium yeasts are desirable... 

---