Selenium is a vital trace element nutrient with multiple roles in the growth and functioning of living cells in higher animals and humans. Almost all of the selenium in animal tissues is found in the proteins. At the molecular level, selenium (as selenocysteine) is an essential component of the active sites of the antioxidant enzyme glutathione peroxidase, and the enzymes participating in thyroid functions - iodothyronine 5'-deiodinase and mammalian thioredoxin reductase. Selenium is also present in several other mammalian selenoproteins. Selenium occurs in foods in the form of the seleno-amino acids (selenomethionine and selenocysteine) and their derivatives. Inorganic salts such as sodium selenate, "organic" chelates, selenium yeast and L-(+)-Selenomethionine are offered for dietary supplementation. L-(+)-Selenomethionine and selenium yeast of good quality (containing most of the elemental selenium in the form of L- (+)-Selenomethionine) are the preferred forms for dietary supplementation.

Sabinsa Corporation offers manufacturers two grades of L-(+)-Selenomethionine: pure L-(+)-Selenomethionine (containing a minimum of 40% selenium) and a triturated product with dicalcium phosphate, which contains 5,000 mcg per gram (0.5%) of selenium. It is important to recognize that "chelates" and "organically bound" forms of selenium are not similar to Sabinsa’s L-(+)-Selenomethionine. Both these forms release inorganic selenium into the body. Sabinsa’s product is unique in that the selenomethionine is a molecularly integrated single chemical entity, containing selenium in place of sulfur in the molecule of the essential amino acid, methionine. This compound is directly incorporated into the body proteins by metabolic pathways similar to those for methionine.

L-(+)-Selenomethionine is not only safer, but more bioavailable than other dry "blended" selenium and methionine products. Organically bound selenium has garnered heavy media attention as a pivotal component in the body’s detoxifying system and for its role in the prevention of disease. It is important that Selenomethionine be present in the L-(+) form in selenium yeast and Selenomethionine supplements. It should be noted that amino acids in living cells are usually present in the L-(+) form. The biological significance of this factor and analytical methodologies developed at Sabinsa Corporation to identify the L-(+) form and differentiate between genuine L-(+)-Selenomethionine samples and physical blends of inorganic selenium salts and methionine are summarized in this article.