Thyroid and cancer-prevention trials studied 200 µg/day for years but do not support routine prevention in the general population
Reviewed · Published
Selenium
Functions in selenoproteins for thyroid-hormone metabolism and antioxidant defense.
Established functions
- Functions in selenoproteins for thyroid-hormone metabolism and antioxidant defense.
Dietary sources
- tuna
- eggs
- meat
Claims and evidence
Claims that Selenium alone prevents or treats disease, or invariably improves health without deficiency, are unsupported.
Japanese reference amounts
- Japanese adults (age and sex as specified): Adults: 25–30 µg/day (RDA)
Amounts studied
- Thyroid and cancer-prevention trials studied 200 µg/day for years but do not support routine prevention in the general population
Tolerable upper limits
- Adults: 400–450 µg/day
Forms and bioavailability
Supplement forms: selenomethionine, sodium selenite
- Selenomethionine is nonspecifically incorporated into body proteins and retained.
Safety and interactions
Adverse effects
- hair loss
- nail changes
- garlic breath
- neurologic symptoms
Medicine and nutrient interactions
- duplicate multivitamins, cisplatin
Contraindications and cautions
- Avoid stacking supplements with high-selenium foods.
Practical selection
- Compare Selenium amount per serving, form, allergens, and batch testing; prefer a single-ingredient product suited to the intended use.
Sources and review
- Dietary Reference Intakes for Japanese (2025)Ministry of Health, Labour and Welfare (Japan)
- NIH ODS mineral fact sheetsNIH Office of Dietary Supplements
Daiki Minaki (editorial and evidence review) ·