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evidence · mechanism · dose
Supplements/Mineral

Selenium

aka Selenomethionine

Trace mineral essential for glutathione peroxidase and thyroid hormone activation.

Immune FunctionHormone OptimizationHealthy Aging

Overview

Trace mineral essential for glutathione peroxidase and thyroid hormone activation.

Natural sources
  • Brazil nuts
  • Seafood
  • Organ meats
Common forms
  • Selenomethionine
  • Selenocysteine
  • Sodium selenite

Forms & variants of Selenium

Different chemical forms of Selenium behave differently. Browse each form's mechanism, bioavailability, and best-use context.

Selenomethionine
Selenomethionine

Organic selenium form — preferred for thyroid (Hashimoto's) and antioxidant support.

Selenium yeast
Selenium-Enriched Yeast

Yeast-bound selenomethionine — form used in major chemoprevention trials.

Mechanism of action

Incorporated into selenoproteins including glutathione peroxidase and deiodinases (T4→T3).

Pathways
  • · Antioxidant defense
  • · Thyroid hormone activation

Effects on the body

Supports
Thyroid hormone conversion
Supports
Antioxidant defense

Organ system effects

Endocrine

Required for T4→T3 deiodination.

Immune System

Modulates NK cell activity.

Evidence-based benefits

Reduces TPO antibodies in Hashimoto's

Moderate evidence

Potential side effects

Common
    Rare
    • · Garlic breath
    Serious
    • · Selenosis (hair loss, nail brittleness) >400 mcg/d

    Drug interactions

    No notable interactions reported.

    Safety & non-supplemental interactions

    Educational summary — always confirm with your clinician or pharmacist before starting, stopping, or combining with prescription therapy.

    Avoid with these conditions
    • ·Autoimmune disease (theoretical immune activation)
    Avoid / monitor with these medications
    • ·Immunosuppressants

    Supplement interactions

    Pairs well with

    None listed.

    Avoid combining with

    No specific avoidances listed.

    Dosing & bioavailability

    Typical dose
    55–200 mcg
    Upper safe limit
    400 mcg

    Where to buy

    Affiliate-style search links to reputable retailers. We don't endorse specific brands — verify third-party testing (USP, NSF, Informed Sport) before purchase.

    Mineral
    Selenium
    Amazon
    Wide selection · fast shipping
    Mineral
    Selenium
    iHerb
    Global delivery · curated brands
    Mineral
    Selenium
    Thorne
    Practitioner-grade · NSF tested

    Scientific evidence (8)

    Systematic reviewExamine.com Supplement Database · 2023

    Selenium: pharmacology, clinical evidence, and safety — narrative review

    Examine.com Research Team

    Curated narrative review of human and preclinical evidence for Selenium, including mechanism, typical dosing, and safety considerations.

    Key findings

    Best-supported outcome: Reduces TPO antibodies in Hashimoto's (evidence: moderate). Additional outcomes and limitations summarized in the full profile.

    Open study
    Systematic reviewPubMed (NLM) · 1970

    PubMed: Selenium — Reduces TPO antibodies in Hashimoto's

    Live PubMed search

    Live results for "Selenium Reduces TPO antibodies in Hashimoto's" across the PubMed/MEDLINE peer-reviewed index.

    Key findings

    Opens current human and preclinical literature matching Selenium and "Reduces TPO antibodies in Hashimoto's". Filter by RCT, meta-analysis, or year on the results page.

    Open study
    Systematic reviewPubMed (NLM) · 1970

    PubMed: Selenium — randomized controlled trial

    Live PubMed search

    Live results for "Selenium randomized controlled trial" across the PubMed/MEDLINE peer-reviewed index.

    Key findings

    Opens current human and preclinical literature matching Selenium and "randomized controlled trial". Filter by RCT, meta-analysis, or year on the results page.

    Open study
    Systematic reviewPubMed (NLM) · 1970

    PubMed: Selenium — meta-analysis

    Live PubMed search

    Live results for "Selenium meta-analysis" across the PubMed/MEDLINE peer-reviewed index.

    Key findings

    Opens current human and preclinical literature matching Selenium and "meta-analysis". Filter by RCT, meta-analysis, or year on the results page.

    Open study
    Systematic reviewPubMed (NLM) · 1970

    PubMed: Selenium — pharmacokinetics

    Live PubMed search

    Live results for "Selenium pharmacokinetics" across the PubMed/MEDLINE peer-reviewed index.

    Key findings

    Opens current human and preclinical literature matching Selenium and "pharmacokinetics". Filter by RCT, meta-analysis, or year on the results page.

    Open study
    Systematic reviewPubMed (NLM) · 1970

    PubMed: Selenium — safety adverse events

    Live PubMed search

    Live results for "Selenium safety adverse events" across the PubMed/MEDLINE peer-reviewed index.

    Key findings

    Opens current human and preclinical literature matching Selenium and "safety adverse events". Filter by RCT, meta-analysis, or year on the results page.

    Open study
    Systematic reviewPubMed (NLM) · 1970

    PubMed: Selenium — dose response

    Live PubMed search

    Live results for "Selenium dose response" across the PubMed/MEDLINE peer-reviewed index.

    Key findings

    Opens current human and preclinical literature matching Selenium and "dose response". Filter by RCT, meta-analysis, or year on the results page.

    Open study
    Systematic reviewGoogle Scholar · 1970

    Google Scholar: Selenium — clinical evidence

    Live Scholar search

    Cross-database citation index for Selenium as it relates to "clinical evidence".

    Key findings

    Includes preprints, theses, and journal articles. Useful for tracking citation counts and follow-on work.

    Open study
    Educational use only. This profile is not medical advice. Consult a qualified healthcare professional before starting any supplement, especially if you take prescription medication or have a chronic condition.