L-Selenomethionine
L-Selenomethionine is a tier 1 form of Selenium, used in 2,703 on-market products and providing 40.3% elemental selenium by weight.
2,703
on-market products
tier 1
quality tier
40.3%
elemental fraction
Basis: C5H11NO2Se, single defined molecule, no hydration ambiguity
Why this tier: Retained longer than inorganic selenite/selenate (organic forms show higher retention; Fairweather-Tait 2010); the form used in SELECT. The NPC trial is reported to have used selenium-enriched yeast (not confirmed from the abstract).
Source: Fairweather-Tait SJ et al. 2010, Am J Clin Nutr 91(5):1484S-1491S, PMID 20200264; Lippman SM et al. 2009, JAMA 301(1):39-51, PMID 19066370; Clark LC et al. 1996, JAMA 276(24):1957-1963, PMID 8971064