L-Selenomethionine
Also known as: selenomethionine, SeMet, organic selenium, selenium (as L-selenomethionine)
The organic selenium form found in Brazil nuts, grains, and selenium yeast, in which selenium replaces sulfur in the amino acid methionine. It is absorbed nearly completely and incorporated into body proteins, giving higher and more sustained blood selenium than inorganic selenite. It is the standard selenium in multivitamins, thyroid, antioxidant, and men's-health formulas. Pure L-selenomethionine is about 40% selenium, but it is almost always supplied as a 0.5–1% dilution on a carrier.
Research summary
Provides selenium for selenoproteins such as glutathione peroxidases and thioredoxin reductases that manage peroxides, and for deiodinases that activate thyroid hormone.
Dosage
Daily amounts, elemental (40% of the compound is the element).
| Lowest studied | Typical range | Highest studied | Upper limit |
|---|---|---|---|
| 50 mcg | 50–200 mcg | 400 mcg | 400 mcg |
NIH ODS — UL of 400 mcg/day for adults from all sources
Doses are micrograms of elemental selenium. L-selenomethionine (MW 196.1) is 40.3% Se by stoichiometry, but the ingredient is normally shipped as a 1% (10,000 mcg/g) trituration on dicalcium phosphate or similar; raw_material_mg_per_dose_unit = 0.1 mg per mcg reflects that dilution — adjust if the supplier's premix differs. Xia 2005 compared selenomethionine and selenite at graded doses in a low-selenium population; SELECT and similar trials used 200 mcg/day, and some studies went to 400–800 mcg. The app caps at the 400 mcg UL. Selenosis (hair and nail brittleness, garlic breath) is the warning sign of chronic excess.
Source material: synthetic L-selenomethionine, usually as a 0.5–1% dilution
As supplied: Typically supplied as a 1% (10,000 mcg/g) trituration; pure SeMet ≈ 40% Se
Forms of Selenium
| Form | Typical dose | Element % | Formats | Price |
|---|---|---|---|---|
| L-Selenomethionine | 50–200 mcg | 40% | Capsule, Powder, Tablet, Gummy, Liquid | low |
| Sodium Selenite | 50–200 mcg | 46% | Capsule, Powder, Tablet, Liquid | low |
Format suitability
- Capsule
- Powder
- Tablet
- Softgel
- Gummy
- Liquid
Micro-dose; the carrier dilution, not the active, sets the fill weight (200 mcg ≈ 20 mg of 1% premix). Blend uniformity matters at these levels.
Formulation notes
Vitamin E is the traditional pairing in antioxidant formulas. High-dose vitamin C in the same serving may slightly reduce absorption of inorganic selenium but has little effect on selenomethionine. Count selenium from selenium yeast or Brazil-nut ingredients toward the total.
- Has an upper limit
Sources
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