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: More complete absorption and greater tissue retention than selenite in comparative reviews; the form used in the two largest human RCTs (NPC, SELECT).
Source: Clark LC et al. 1996, JAMA 276(24):1957-1963; Lippman SM et al. 2009, JAMA 301(1):39-51