Selenium (as Se-methyl-L-selenocysteine)


Se-Methyl-L-Selenocysteine | Methyl Seleno Cysteine | Methylselenocysteine | MSC


  • Supports general immune health*
  • Supports thyroid health*


Selenium (Se) has been recognized as an essential trace mineral since 1957; about 25 different selenium-containing proteins have been identified in humans[1]. Selenium is critical for immune function, thyroid function, reproductive health, DNA synthesis, and antioxidant defenses[1,2]. Selenium concentration is highest in the thyroid gland, while muscles, liver and bone are the largest reservoirs of selenium. In foods, selenium is mostly found as selenomethionine, selenocysteine, and Se-methyl-L-selenocysteine (organic selenium). Selenium is found in soils as selenate and selenite (i.e., referred to as inorganic forms), which plants convert into organic forms. Brazil nuts are the best food source, with a single nut, on average, containing about the recommended dietary allowance (RDA) of selenium[3]. Fish, meat, poultry, mushrooms, and legumes are good sources of selenium. Most ingested selenium is converted into selenoproteins (i.e., proteins that have a selenocysteine)—selenoproteins are a member of the selenol class of organoselenium compounds. The selenoproteins are needed for antioxidant enzymes (e.g., glutathione peroxidase, thioredoxin reductase) and the enzymes that convert one thyroid hormone to another. Se-methyl-L-selenocysteine (MSC) is one of the organic forms of selenium: Most of the selenium found in Allium (e.g., garlic, leeks, onions) and Brassica (e.g., broccoli, cannage, cauliflower) species is MSC[4,5]. Selenium’s name derives from the ancient Greek word for moon—selḗnē. 


Se-methyl-L-selenocysteine is a bioavailable and safe organic form (i.e., one of the forms found in foods) of selenium. It can be used in the selenium-containing proteins that cells need to stay healthy.

Se-methyl-L-selenocysteine is produced by Sabinsa.

Se-methyl-L-selenocysteine is GRAS, non-GMO, gluten-free, Halal, and vegan.


We chose Se-methyl-L-selenocysteine because it (1) is one of the bioavailable forms of selenium, (2) can be converted into selenium-containing proteins, and (3) may be the best form of selenium for helping cells counter changes caused by cellular stress and aging. To ensure against inadequacy, in the United States the recommended dietary allowance (RDA) of selenium for adults is currently set at 55 mcg (ug) per day, which is an amount sufficient to support selenoprotein levels in healthy adults. Selenium follows hormetic principles (see Neurohacker Dosing Principles). The key point is that selenium is not a “more is better” trace mineral—the tolerable upper limit for adults has been set at 400 mcg per day. When determining the dose of selenium to include in a product, our goal is to ensure we’ve supplied an amount consistent with the product’s goals while being within the hormetic range. If the product is intended to be supplemented for extended periods of time in healthy adults, who would be expected to have adequate selenium status, we believe that the dose used should be an amount on the lower end of the range (i.e., the RDA amount).


Immune function

  • Supports general immune health[1,6–10]
  • Supports innate immunity[11–16]
  • Supports adaptive immunity[7,8,11–15,17]
  • Supports immune tolerance[18–38] 
  • Supports immune signaling[39–41]   
  • Supports healthy natural killer cell function[11–16,42–44]
  • Supports healthy macrophage function[45–47]   
  • Supports healthy microglial function[48,49]
  • Supports healthy neutrophil function[50–58]
  • Supports healthy mast cell function[59–61]  
  • Supports healthy T cell function[8,11–15,17]
  • Supports healthy B cell function[8,60]

Thyroid function

  • Supports thyroid function[19–21,23–37,62]

Gut microbiota

  • Supports a healthy gut microbiota[63–65]

Healthy aging

  • Supports Healthspan (Caenorhabditis elegans)[66,67]
  • Supports mitochondrial function[68–74]
  • Supports Nrf2[75–84]
  • Supports antioxidant defenses[2]
  • Supports sirtuin activity[85]
  • Supports circadian function[85–87]

Complementary ingredients

  • Zinc in supporting immunity[10,88]
  • Zinc, vitamin C and E, and beta-carotene for cognitive function during aging[89]


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