Selenium is part of antioxidant enzymes and thyroid hormone metabolism. Soil levels vary a lot by region.
Calculator Official intake Study doses Best form Safety Sources
AI (adequate intake)
| Men | 70 µg |
|---|---|
| Women | 70 µg |
| Pregnancy | 70 µg |
| Breastfeeding | 85 µg |
Safe upper limit: 255 µg a day
RDA (recommended dietary allowance)
| Men | 55 µg |
|---|---|
| Women | 55 µg |
| Pregnancy | 60 µg |
| Breastfeeding | 70 µg |
Safe upper limit: 400 µg a day
Source: National Academies (NASEM) 2019
These are doses tested in research, not personal advice. Some exceed the upper limit because they were short courses or given under medical care.
200 µg a day
SELECT gave healthy men 200 µg selenium a day. It did not lower prostate cancer.
200 µg a day
Meta-analysis (Thyroid 2016): around 200 µg selenium a day for 3 to 12 months lowered thyroid peroxidase antibodies in people with Hashimoto's on thyroid hormone. It is not clear that this improves symptoms or thyroid function. Discuss with your doctor.
No clear winner
Label shows elemental amount (a good choice among equals)
Why: Selenomethionine, selenium yeast, sodium selenite and selenate are all absorbed well, up to about 90%. Labels give elemental selenium, which is what to compare.
Alternatives: Brazil nuts are very rich in selenium (68 to 91 µg per nut) and vary a lot, so regular large amounts can be too much.
Brazil nuts (very high and variable), fish, eggs, meat.
Count Brazil nuts: one nut can contain a lot of selenium.
Too much causes brittle hair and nails and a garlic breath odour. EFSA lowered its safe limit to 255 µg in 2023.
Pregnant, breastfeeding, on medication, or managing a health condition? Check with a doctor or pharmacist before starting a supplement.
Values checked: November 12, 2026.
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