L-Selenomethionine vs. Selenium Amino Acid Chelate
Among 4,693 on-market selenium products with an identifiable primary form, 57.5% use L-Selenomethionine (2,697 products) and 17.3% use Selenium Amino Acid Chelate (811).
| L-Selenomethionine | Selenium Amino Acid Chelate | |
|---|---|---|
| Quality tier | Tier 1 | Unrated |
| Selenium by weight | 40.3% | — |
| Share of market | 57.5% | 17.3% |
| On-market products | 2,697 | 811 |
| Median declared dose | 70 elemental mcg middle half: 35–105 | 50 elemental mcg middle half: 20–100 |
| Most common brands | Pure Encapsulations, GNC Mega Men, Carlson | Airborne, Ultima, Douglas Laboratories |
Doses are declared per serving in elemental mcg. “By weight” is the share of the ingredient that is the nutrient itself (e.g. elemental magnesium in a magnesium salt).
Why L-Selenomethionine is tier 1
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
Why Selenium Amino Acid Chelate is unrated
Terminology inconsistent across manufacturers; needs manual review to determine actual composition.
Source: uncertain -- needs review
Tiers summarize published comparative bioavailability or outcome evidence for each form (see methodology).
This page describes the market; it is not a recommendation to take either form. Talk to a clinician about what's right for you.