L-Selenomethionine
Also known as: Selenium (organic form), Selenomethionine, SeMet
Selenium is an essential trace element required for selenoproteins including glutathione peroxidases and thyroid-hormone deiodinases. Selenomethionine raises selenium status more effectively per microgram than inorganic selenite, though selenium nutrition follows a U-shaped curve — both deficiency and excess are harmful.
Last reviewed: 2026-10-06 · 0 indexed studies
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Overview
L-selenomethionine is the organic, amino-acid-bound form of selenium and the main form found in foods. It is absorbed efficiently and incorporated into body proteins, providing a slow-release selenium pool.
Mechanism & Function
Mechanism of Action
Absorbed via methionine transporters, selenomethionine enters the methionine pool and is gradually metabolised to selenide, the precursor for selenocysteine insertion into selenoproteins.
Physiological Role
Selenium is essential for glutathione peroxidase (antioxidant defence), iodothyronine deiodinases (thyroid hormone activation) and thioredoxin reductases.
Primary Pathways
Performance / Health Relevance
Relevant where selenium status is low (low-soil-selenium regions); no performance benefit when status is adequate.
Evidence Review
No human clinical studies indexed for this ingredient yet.
No meta-analyses or systematic reviews indexed for this ingredient yet.
Dimensions marked N/A have no indexed evidence of that class. They are shown as unavailable rather than scored.
Practical Use & Dosage
- Minimum Effective Dose
- 55 µg/day (adult RDA for selenium)
- Optimal Range
- 55–200 µg/day total selenium from all sources
- Upper / Caution Level
- 400 µg/day (tolerable upper intake level); chronic excess causes selenosis
- Timing
- Daily, with food
- Best Format
- L-selenomethionine (organic) — better retained than selenite
- Bioavailability
- High absorption (~90%); retained in body protein pools.
- Absorption Considerations
- Count total selenium intake from diet plus supplements to avoid excess.
Safety & Interactions
Side Effects
- •Selenosis at chronic high doses (garlic breath, brittle nails, hair loss)
Contraindications
- High dietary selenium intake
Drug Interactions
- •None major; cisplatin interaction reported (theoretical)
Who Should Avoid
- •People already consuming selenium-rich diets or multiple fortified products
Monitoring
Avoid stacking multiple selenium-containing supplements.
Frequently Asked Questions
Auto-generated from indexed evidence — dosage, safety, interactions, and more.
When is L-Selenomethionine typically used or indicated?
L-Selenomethionine is most commonly used for: Selenium repletion, Thyroid-support formulas, Antioxidant-enzyme support. Selenium is essential for glutathione peroxidase (antioxidant defence), iodothyronine deiodinases (thyroid hormone activation) and thioredoxin reductases.
How does L-Selenomethionine work?
Absorbed via methionine transporters, selenomethionine enters the methionine pool and is gradually metabolised to selenide, the precursor for selenocysteine insertion into selenoproteins.
What is the recommended dose of L-Selenomethionine?
The optimal range is 55–200 µg/day total selenium from all sources. with a minimum effective dose of 55 µg/day (adult RDA for selenium). Best taken: Daily, with food. Upper / caution level: 400 µg/day (tolerable upper intake level); chronic excess causes selenosis.
What are the side effects of L-Selenomethionine?
Reported side effects include: Selenosis at chronic high doses (garlic breath, brittle nails, hair loss). Monitoring: Avoid stacking multiple selenium-containing supplements.
Does L-Selenomethionine interact with medications?
Known or theoretical interactions: None major; cisplatin interaction reported (theoretical). Always check with a clinician before combining with prescription medication.
Who should avoid L-Selenomethionine?
L-Selenomethionine is generally not recommended for: People already consuming selenium-rich diets or multiple fortified products; and High dietary selenium intake.
How strong is the evidence for L-Selenomethionine?
Evidence level: Limited (overall score 50/100), based on 0 indexed studies on SuppIndex.
Research & References (0)
No studies match this filter
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Research Overview
Limited EvidenceCite this ingredient
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Stable URL
https://thesuppindex.com/ingredients/l-selenomethionine
SuppIndex. (2026). L-Selenomethionine: Evidence summary, dosage and clinical studies. Retrieved October 16, 2026, from https://thesuppindex.com/ingredients/l-selenomethionine
Based on 0 indexed studies · Evidence level: Limited.
Goal Ratings
Stack Compatibility
Common in thyroid formulas with iodine and zinc; pairs with vitamin E historically.