Selenium

Selenium

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Summary

Selenium is an essential trace mineral that supports antioxidant enzymes (e.g., glutathione peroxidases) and thyroid hormone metabolism. In adults, repleting low selenium can support energy, mood, and immune function; excess intake can be harmful.

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Selenium — Thorne
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Selenium
An essential mineral that supports heart health, thyroid function, and optimal immune function. NSF Certified for Sport®.
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Mental Clarity, Focus, and Energy

  • Indirect benefits: In low status, normalization may improve fatigue and mood; little benefit is expected if selenium intake is adequate.

Brain Health

  • Mechanisms: Antioxidant defense via selenoproteins and support for thyroid hormone activation, which influences cognition and mood.
  • Human cognition data are mixed outside deficiency states.

Gut Health

  • Generally well tolerated; take with food to reduce nausea. Brazil nuts are a food‑based alternative but vary in selenium content.

Brain-Gut Axis

  • By supporting thyroid and antioxidant systems, selenium may reduce stress‑related gut–brain signaling indirectly.

Evidence Summary

Benefit Area
Evidence Quality
Effect Noted
Notes
Mental Clarity
Limited–Moderate
Small gains in low selenium
Status dependent
Focus Enhancement
Limited
Indirect via thyroid/antioxidant effects
No benefit when replete
Energy Support
Limited–Moderate
Reduced fatigue in low status
Individualized dosing
Brain Health
Limited–Moderate
Antioxidant and thyroid support
Mixed human endpoints
Gut Health
Limited
Generally well tolerated
With food
Brain–Gut Optimization
Emerging
Lower oxidative stress
Indirect evidence

Typical Dosing Instructions

  • Standard dose: 100–200 mcg/day from selenomethionine (adjust based on diet and labs)
  • Timing: With meals
  • Notes: Do not exceed upper intake level (UL ~400 mcg/day) from all sources; personalize to labs and diet

Safety Considerations

  • General safety: Avoid excess; chronic high intake can cause selenosis (hair/nail changes, GI upset)
  • Common effects: Nausea at high single doses
  • Contraindications and cautions: Interactions with certain chemotherapeutics and antidiabetic medications are possible; consult clinician
  • Populations: Use under clinician guidance in pregnancy
  • Monitoring: Track selenium intake from diet plus supplements; consider periodic labs in long‑term users
 

References

  1. Selenium Fact Sheet for Health Professionals, NIH Office of Dietary Supplements, 2025-09-25
  1. Selenium and human health: a review of evidence for health effects, Antioxidants, 2022-03-15
  1. Effects of selenium supplementation on thyroid autoimmunity: a systematic review and meta‑analysis of randomized controlled trials, Thyroid, 2023-07-10
  1. Selenium supplementation and mood or quality‑of‑life outcomes: a systematic review of randomized trials, Nutrients, 2021-11-02
  1. Selenium status and cardiovascular health: umbrella review of systematic reviews and meta‑analyses, Frontiers in Nutrition, 2024-05-28
  1. Dietary selenium intake and biomarkers: variability of Brazil nuts and implications for supplementation, Journal of Trace Elements in Medicine and Biology, 2016-09-01
  1. Selenoproteins and the thyroid: from molecular mechanisms to clinical implications, Endocrine Reviews, 2020-08-12