Selenium C
Deficiency is harmful, but supplements above the requirement do not improve performance and are toxic
Citable fact
«Selenium» — evidence level C. Dosage: The adult requirement is 55 µg per day. In supplements, 55–200 µg is acceptable; the upper safe level is 400 µg per day. Chronic intake above 400 µg causes selenosis: brittle nails, hair loss, garlic breath, neurological symptoms. Source: PMID 33203106, permanent link to the source in the list below.
How it works
It is part of glutathione peroxidases and thioredoxin reductase, providing antioxidant protection, and is required by deiodinases that convert T4 to T3. Deficiency impairs antioxidant protection and thyroid function.
Dosage and intake
The adult requirement is 55 µg per day. In supplements, 55–200 µg is acceptable; the upper safe level is 400 µg per day. Chronic intake above 400 µg causes selenosis: brittle nails, hair loss, garlic breath, neurological symptoms.
With food; the time of intake does not affect the effect.
Forms
Selenomethionine, sodium selenate and yeast selenium have been studied; selenomethionine accumulates better in tissues.
What is confirmed
- Corrects the deficiency that occurs in regions with selenium-poor soils
- Supports glutathione peroxidase activity and thyroid function
Adverse effects and limitations
- Above 400 µg per day — selenosis with damage to nails, hair and the nervous system
- The therapeutic window is narrow: the difference between the norm and a toxic dose is small
- Selenium at doses of about 200 µg per day has been linked to an increased risk of type 2 diabetes and aggressive prostate cancer
Interactions
- Enhances the anticoagulant effect of warfarin
- Reduces the effectiveness of some chemotherapy drugs — only as prescribed by a doctor
Who must not use it
- Under 18 years: The requirement is 20–55 µg per day depending on age; supplements are not needed without indications.
- Pregnancy and lactation: The requirement is 60–70 µg per day; high doses are toxic — only as prescribed by a doctor.
- history of selenosis
- type 2 diabetes mellitus
- cancer under active treatment
- iodine deficiency
Sources
- Antioxidants and Exercise Performance: With a Focus on Vitamin E and C Supplementation · Higgins MR, Izadi A, Kaviani M · International journal of environmental research and public health, 2020 · PMID 33203106
- Micronutrients and athletic performance: A review · Beck KL, von Hurst PR, O'Brien WJ · Food and chemical toxicology : an international journal published for the British Industrial Biological Research Association, 2021 · PMID 34662692
See also
Open in the app
This page holds reference data with links to studies. In the app you can calculate calories and macros for your goal, build a personal supplement stack and review weekly training volume.