Thorne Selenium 200 mcg – Selenomethionine | Supports Thyroid, Antioxidant, Immune & Cardiovascular Health, 60 Capsules

What Is Thorne Selenium 200 mcg?

Thorne Selenium 200 mcg delivers 200 micrograms of selenium per capsule as Selenomethionine — the most bioavailable, organic form of selenium, in which selenium is bound to the amino acid methionine exactly as it occurs naturally in selenium-rich foods such as Brazil nuts, fish, meat, and eggs. Selenomethionine is absorbed via the same active amino acid transport pathway as methionine itself, achieving significantly higher and more consistent tissue selenium retention compared to inorganic forms (sodium selenite, sodium selenate). Selenium is an essential trace mineral that serves as the catalytic center of an entire family of selenoprotein enzymes — including glutathione peroxidases, thioredoxin reductases, and iodothyronine deiodinases — making it indispensable for antioxidant defense, thyroid hormone metabolism, immune function, and cardiovascular health. NSF Certified for Sport®.

Why Selenomethionine Is the Superior Form

• Organic vs. Inorganic Selenium — Inorganic selenium (selenite, selenate) is absorbed passively via a less efficient mechanism and has lower bioavailability and tissue retention. Selenomethionine is absorbed actively via methionine transporters with absorption rates of 90%+ and is stored in body proteins (substituting for methionine) creating a selenium reservoir that is released gradually as needed
• Higher Tissue Retention — Studies consistently show selenomethionine achieves significantly higher selenium tissue levels per microgram consumed compared to inorganic selenium forms, making it more effective at raising selenium status in deficient individuals
• Food-State Analogous — Selenomethionine is the predominant form of selenium in plant foods and animal proteins — the same form the body has evolved to absorb and utilize most efficiently

What Does Selenium Do?

• Thyroid Hormone Metabolism — Critical Selenoprotein Function — Selenium is the catalytic center of iodothyronine deiodinase enzymes (Types I, II, III) — the selenoproteins responsible for converting inactive thyroid hormone T4 (thyroxine) to active T3 (triiodothyronine) in peripheral tissues, and for regulating T3 degradation. Without adequate selenium, T4-to-T3 conversion is impaired even when iodine and TSH are normal, resulting in subclinical hypothyroid symptoms despite normal standard thyroid panels. Selenium also protects thyroid gland cells from the hydrogen peroxide generated during thyroid hormone synthesis (required by thyroid peroxidase/TPO) via Glutathione Peroxidase 3 (GPx3), the dominant antioxidant enzyme in thyroid tissue
• Antioxidant Defense — Glutathione Peroxidase System — Selenium is the active site mineral in all five Glutathione Peroxidase (GPx1–5) enzymes — the body’s primary enzymatic antioxidant defense system for neutralizing hydrogen peroxide and lipid hydroperoxides in both cytoplasmic and mitochondrial compartments. GPx enzymes work in concert with Vitamin C and Vitamin E to form a layered antioxidant defense network protecting every cell from oxidative damage
• Immune System Modulation — Selenium is required for the proliferation and activity of multiple immune cell types including T lymphocytes, natural killer (NK) cells, and neutrophils. Selenium deficiency impairs both innate and adaptive immune responses, increases susceptibility to viral infection, and may promote viral mutation toward more virulent strains (demonstrated in influenza and other RNA viruses). Adequate selenium supports vaccine efficacy and immune resilience
• Cardiovascular Protection — Selenoproteins (particularly thioredoxin reductases and GPx1) protect the heart muscle and vascular endothelium from oxidative damage. Selenium deficiency is associated with Keshan disease (a severe cardiomyopathy) in severely deficient populations, and with increased cardiovascular risk in moderately deficient individuals. Selenium supports healthy LDL oxidation resistance and platelet function
• Anti-inflammatory Activity — Thioredoxin reductases (TrxR1, TrxR2) — selenoproteins — regulate the thioredoxin system, which controls redox-sensitive inflammatory transcription factors including NF-κB and AP-1. Adequate selenium helps maintain appropriate inflammatory homeostasis and reduces chronic low-grade inflammation
• Male Reproductive Health — Selenium is highly concentrated in testicular tissue and is essential for sperm formation (spermatogenesis), sperm motility, and sperm DNA integrity via the selenoprotein GPx5 and Selenoprotein P. Selenium deficiency is associated with reduced sperm count, poor motility, and increased sperm DNA fragmentation
• DNA Integrity & Cancer Risk Reduction — Selenium supports DNA repair mechanisms and has been extensively studied for its potential role in reducing oxidative DNA damage. The SELECT trial and multiple epidemiological studies have explored selenium’s relationship with cancer risk, particularly prostate, colorectal, and lung cancers, though optimal dosing and form are still under investigation

Selenium Deficiency — Who Is at Risk?

Selenium content in food is entirely dependent on soil selenium levels, which vary enormously by geography. Large regions of Europe, China, New Zealand, and parts of the Middle East have selenium-depleted soils, resulting in systematically low dietary selenium intake in populations living there. Risk factors include:

• Living in or sourcing food from selenium-depleted soil regions
• Vegan and vegetarian diets (plant foods have lower and more variable selenium than animal proteins)
• Inflammatory bowel disease, celiac disease, or other malabsorption conditions
• Chronic kidney disease (increased selenium losses)
• Thyroid disorders (Hashimoto’s thyroiditis — see below)

Selenium & Hashimoto’s Thyroiditis

Selenium has specific clinical relevance for Hashimoto’s autoimmune thyroiditis — the most common cause of hypothyroidism. Multiple randomized controlled trials have shown that selenium supplementation (200 mcg/day as selenomethionine) significantly reduces thyroid peroxidase antibody (TPO-Ab) titers in Hashimoto’s patients, modulates autoimmune activity, and may slow thyroid gland destruction. This is the most evidence-backed nutritional intervention for autoimmune thyroid disease management.

Who Should Take This?

• Individuals with Hashimoto’s thyroiditis or autoimmune thyroid disease (under medical supervision)
• Those with suboptimal thyroid function, impaired T4-to-T3 conversion, or thyroid symptoms despite normal TSH
• People in selenium-depleted geographic regions or on vegan/vegetarian diets
• Athletes seeking antioxidant support for exercise-induced oxidative stress
• Men supporting sperm health and male reproductive function
• Individuals supporting immune resilience, cardiovascular health, and anti-inflammatory defense
• Competitive athletes requiring NSF Certified for Sport® verified supplements

How to Use

Take 1 capsule daily with a meal, or as directed by your healthcare practitioner. 200 mcg/day is the most commonly used therapeutic dose in clinical research. Do not exceed 400 mcg/day from all sources (food + supplements combined) as selenium has a narrow therapeutic window and chronic excess can cause selenosis. Selenium status can be assessed via plasma selenium or selenoprotein P levels — testing before and during supplementation is recommended for targeted thyroid or immune protocols.

Product Highlights

• 200 mcg Selenium as Selenomethionine — highest bioavailability organic form
• 90%+ absorption via active amino acid transport pathway
• Activates Glutathione Peroxidase (GPx) system — primary enzymatic antioxidant defense
• Supports T4-to-T3 Thyroid Hormone Conversion via Iodothyronine Deiodinase selenoproteins
• Clinically studied for Hashimoto’s TPO antibody reduction at 200 mcg/day
• Supports Immune Defense, Cardiovascular Health & Male Reproductive Function
• 60 Capsules | NSF Certified for Sport® | No unnecessary excipients
• From Thorne — trusted by healthcare practitioners worldwide