Selenium

Also known as: selenium methionine, selenomethionine, selenium yeast

Grade B — Moderate Evidencemineraltraceantioxidant
100–200 mcgWith food. Do not exceed 400mcg/day.

Selenium is an essential trace mineral that serves as a cofactor for glutathione peroxidase and other selenoproteins critical for antioxidant defense and thyroid hormone metabolism. It is required for the conversion of T4 to T3, and supplementation has been shown to reduce thyroid peroxidase antibodies in Hashimoto's thyroiditis. The therapeutic window is narrow — 200mcg/day is the evidence-backed dose, while exceeding 400mcg risks selenosis.

TL;DR: Essential trace mineral for thyroid function (T4→T3 conversion) and antioxidant defense. Reduces Hashimoto's antibodies.

🛡️Immunity🧬Longevity✨Skin & Hair
Last reviewed: 2026-03-12

Quick Facts

Evidence

Grade B

Studies

3

Interactions

2

Forms

1

Evidence Rating: Grade B — Moderate Evidence

Some RCTs with positive results, or strong observational evidence. More research may refine our understanding.

Interaction Warnings

Blood thinnersLow

High doses may increase bleeding risk

Vitamin C (selenite form)Low

May reduce selenite absorption; less relevant with selenomethionine

Important Notes

  • Do not exceed 400mcg/day — selenosis risk
  • Brazil nuts: 1-2/day often sufficient (70-90mcg/nut)
  • Narrow therapeutic window

Clinical Evidence (3 studies)

Selenium and human health

Rayman MP (2012) — Lancet

Comprehensive review: thyroid, cancer, cardiovascular, immune benefits

View on PubMed

Selenium reduced TPO antibodies in Hashimoto's

Gärtner R et al. (2002) — J Clin Endocrinol Metab

200mcg/day significantly reduced TPO antibodies

View on PubMed

Meta-analysis of selenium in Hashimoto's thyroiditis

Toulis KA et al. (2010) — Thyroid

4 RCTs: consistent TPO-Ab reduction

View on PubMed

Alternatives to Consider

These supplements target similar goals and may be worth considering alongside or instead of Selenium.

Vitamin C

Grade A

Essential antioxidant vitamin. Supports immune function, collagen synthesis, and antioxidant defense. 50% infection reduction in athletes.

🛡️ Immunity✨ Skin & Hair🧬 Longevity

Zinc

Grade A

Essential mineral for immune function, wound healing, and testosterone production. Lozenges reduce cold duration by ~33%.

🛡️ Immunity✨ Skin & Hair

NAC (N-Acetyl Cysteine)

Grade B

Precursor to glutathione (master antioxidant). Strong evidence for respiratory health, liver support, and psychiatric conditions.

🛡️ Immunity🧬 Longevity

Related Supplements

Vitamin C

Grade A — Strong Evidence

Essential antioxidant vitamin. Supports immune function, collagen synthesis, and antioxidant defense. 50% infection reduction in athletes.

NAC (N-Acetyl Cysteine)

Grade B — Moderate Evidence

Precursor to glutathione (master antioxidant). Strong evidence for respiratory health, liver support, and psychiatric conditions.

Zinc

Grade A — Strong Evidence

Essential mineral for immune function, wound healing, and testosterone production. Lozenges reduce cold duration by ~33%.

Astaxanthin

Grade C — Preliminary

Extremely potent antioxidant carotenoid. Promising for skin health and exercise recovery. Still building human evidence.

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⚕️ Important Disclaimer

This information is for educational purposes only. It is not medical advice. Always consult a healthcare provider before starting any supplement regimen, especially if you take medications or have health conditions.

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