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
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
Why Selenium Amino Acid Chelate is unrated
Terminology inconsistent across manufacturers; composition cannot be determined from the name alone.
Source: none (definitional caveat; no source defines the composition of "selenium amino acid chelate")