Selenomethionine · Selenium Yeast
Selenium is an essential trace mineral and cofactor for 25+ selenoproteins including glutathione peroxidases (the body's primary antioxidant enzyme system), thioredoxin reductases, and iodothyronine deiodinases (which convert T4 to active T3 thyroid hormone). Selenium is found in highest concentrations in Brazil nuts (the richest natural source - 1-2 nuts can provide an entire day's RDA), seafood (tuna, sardines, halibut), organ meats, eggs, and selenium-enriched soils (soybeans, sunflower seeds, garlic).
Take with food. 100mcg is daily RDA-level supplementation; 200mcg is therapeutic for autoimmune thyroid. Brazil nuts (1-2 daily) provide approximately equivalent dose. Selenomethionine is the most bioavailable form. Do NOT exceed 400mcg/day chronic - selenosis risk.
Start here. Every protocol below is ordered lowest-first. Begin at the smallest effective dose, hold about a week to assess tolerance, and step up only if needed.
Selenium's primary mechanism is incorporation into selenoproteins as the rare amino acid selenocysteine (Sec, the 21st amino acid in proteins). Twenty-five selenoproteins are encoded in the human genome, with the most clinically important being: glutathione peroxidases (GPx1-8) which neutralize hydrogen peroxide and lipid peroxides; thioredoxin reductases (TrxR1-3) which maintain redox homeostasis; and iodothyronine deiodinases (DIO1-3) which convert thyroid hormones (T4 to T3 conversion).
The thyroid mechanism is particularly relevant for autoimmune thyroid disease. Selenoproteins protect thyroid follicular cells from peroxide damage during thyroid hormone synthesis - a process that inherently generates reactive oxygen species. In Hashimoto's thyroiditis, selenium supplementation reduces oxidative damage and antibody-mediated destruction, leading to lower TPO antibody titers, improved thyroid function in subclinical hypothyroidism, and reduced inflammation. The deiodinase enzymes also depend on selenium for T4-to-T3 conversion, so deficiency can reduce active thyroid hormone availability.
Beyond thyroid effects, selenium's antioxidant role through GPx and TrxR is broadly cell-protective. Selenium also has direct anti-cancer mechanisms via apoptosis induction in cancer cells (especially methylselenocysteine), heavy metal binding (selenium binds mercury, cadmium, and arsenic, reducing their toxicity), and immune support. The relationship between selenium and cardiovascular disease is U-shaped - both deficiency and excess increase risk.
Days 1-14: Antioxidant pathway support.
Each reference below was re-fetched from its PubMed record, and the quoted sentence was confirmed to appear in that abstract and to support the claim it sits under. Follow any of them to read the source.
Selenium (Se), an essential trace element, plays a pivotal role in thyroid hormone synthesis and antioxidant defence mechanisms.
Selenium (Se), an essential trace element, plays a pivotal role in thyroid hormone synthesis and antioxidant defence mechanisms.
Selenium status and supplementation in thyroid disorders: A narrative review of current evidence.
Evidence scope. Narrative review; general selenium biology, not evidence for the exact 100 mcg supplement regimen.
Claims we could not support
No abstract we checked supports these for this molecule at this route. That is not the same as saying they are false — it marks where the evidence is missing.
Dose/route: 100mcg via Oral, Daily. No checked live PubMed abstract supported this complete molecule/formulation/route/dose/frequency combination.
Primary safety claim: Generally well tolerated at standard doses (100-200mcg/day). No checked live abstract directly established this as the primary concern for the card's exact formulation and regimen.
Two different questions: what is documented about running these together, and what is documented about drawing them into the same syringe. A good pharmacological partner can still have to be pinned separately.
Check any specific pair in the Stack & Interaction Checker, which answers both questions separately. Absence of a documented conflict is not evidence of safety.
No plasma curve is shown here. The half-life on record is a whole-body figure — how long the body takes to turn over its stores — not how long a dose stays in the bloodstream, and the two are not interchangeable.
Whole-body, slow turnover
Oral
~weeks to months (depending on tissue stores)
High (~80-90%) for selenomethionine; lower for sodium selenite (~50%).
Selenoprotein synthesis sustained with daily intake. Tissue levels stable for weeks once steady-state reached.
Renal excretion (predominantly), some via stool. Methylated forms preferentially excreted in breath (garlic odor at high doses).
Storage. Store at room temperature (20-25C) in a cool, dry place. Capsules and tablets shelf-stable for 24+ months. Liquid forms should be refrigerated after opening.
Classified as a dietary supplement in the US. RDA is 55mcg/day for adults. Tolerable Upper Intake Level (UL) is 400mcg/day. Available widely over the counter. Multiple commercial forms (selenomethionine, selenium yeast, sodium selenite, methylselenocysteine).
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