The need for selenium is well recognized in human and animal nutrition. Although it was believed, in the 1930’s, to be the toxic portion of seleniferous plants, many decades of research on the occurrence, metabolism, and toxicity of selenomethionine (the natural organic food form of selenium) ultimately led to selenium’s acceptance as a dietary supplement.
Selenomethionine cannot be synthesized by higher animals. Select strains of yeast and bacteria that are grown in selenium-rich media incorporate selenium as selenomethionine and synthesize it analogously with methionine. The selenomethionine in Selen-E is synthesized by brewer’s yeast.
Unlike the selenite or selenate forms of selenium, only selenomethionine is incorporated into body proteins. After absorption in the small intestine, any amount not immediately needed is stored in organs with a high rate of protein synthesis, such as the brain. Selenomethionine is released into plasma albumin from storage tissue when needed. The content in skeletal muscle reflects dietary intake. Selenomethionine’s half-life is about one-and-a-half times that of selenite. In nursing mothers supplementing with selenomethionine (compared to mothers consuming a selenite form of supplementation), significantly more selenium appeared in the milk.
Compared to selenite or selenate, selenomethionine has a differential effect on lymphocyte proliferation and other immunological biomarkers. A 1991 study demonstrated, for the first time, the immunostimulatory properties of selenium-enriched yeast in elderly humans. Selenomethionine has been shown to protect amino acids and proteins from radiation damage and, in mice, against UV-induced skin damage.
Both selenium and methionine are needed for glutathione peroxidase synthesis. In an individual with adequate methionine, selenomethionine supplementation causes tissue levels of selenium to increase proportionate to the dosage. Thereafter, a steady state is established. This takes about six weeks of supplementation in the erythocytes.
Typical dietary selenium intakes in the US range from 80 to 165 mcg/ day. The current total daily amount of selenium considered safe for an American on a “normal” diet is 200 mcg.*
Directions:
Take one softgel daily or as directed by your healthcare practitioner.
References:
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2. Guo X, Wu L. Distribution of free seleno-amino acids in plant tissue of Melilotus indica L. grown in selenium-laden soils. Ecotoxicol. Environ. Safety 1998;39:207-214[Medline]
3. Schrauzer GN. Selenomethionine and selenium yeast: appropriate forms of selenium for use in infant formulas and nutritional supplements. J. Med. Foods 1998;1:201-206
4. Vendeland SC, et al. Uptake of selenite, selenomethionine and selenate by brush border membrane vesicles isolated from rat small intestine. Biometals 1994;7:305-312[Medline]
5. Grønbaek H, Thorlacius-Ussing O. Selenium in the central nervous system of rats exposed to 75-Se selenomethionine and sodium selenite. Biol. Trace Elem. Res. 1992;35:119-127[Medline]
6. Oster O, Schmiedel G, Prellwitz W. The organ distribution of selenium in German adults. Biol. Trace Elem. Res. 1988;15:23-45[Medline]
7. Patterson B, Levander O, Helzsouer K, McAdam P, Lewis S, Taylor P, Veillon C, Zech LA. Human selenite metabolism. A kinetic model. Am. J. Physiol. 1989;257:R556-R567
8. McGuire MK, et al. Selenium status of lactating women is affected by the form of selenium consumed. Am. J. Clin. Nutr. 1993;58:649-652
9. Borella P, et al. Chemical form of selenium greatly affects metal uptake and responses by cultured human lymphocytes. Biol. Trace Elem. Res. 1995;51:43-54
10. Peretz A, et al. Lymphocyte response is enhanced by supplementation of elderly subjects with selenium-enriched yeast. Am. J. Clin. Nutr. 1991;53:1323-1328
11. Burke KE, et al. The effects of topical and oral L-selenomethionine on pigmentation and skin cancer induced by ultraviolet irradiation. Nutr. Cancer 1992;17:123-137
12. Shimazu F, Tappel AL. Selenoamino acids decrease radiation damage to amino acids and proteins. Science (Washington DC) 1964;143:369-371
