Selenium
Selenium is an essential trace mineral that the body builds into proteins called selenoproteins. It comes from foods such as Brazil nuts, fish and grains.
What it is studied for
The strongest rated effects first. Bars show the size of the effect, the letter grades the evidence, and each rating lists the studies behind it.
What does selenium do?
Selenium is an essential mineral involved in thyroid hormone metabolism, reproduction, and antioxidant defenses. 1
Who might need a closer look?
BfR identifies people eating a vegan diet and those with some absorption disorders as groups at risk of inadequate intake. A varied diet usually supplies enough. 2
Key studies
The most recent publications linked to Selenium's ratings.
Why people take it
SuppCo community snapshot, 2026-09-28. Reasons for use are not evidence that it works.
Questions people ask
Is selenium necessary for the thyroid?
Yes, but its normal biological role does not establish that extra selenium prevents hypothyroidism. 1 3
Can a lower antibody result prove treatment success?
The thyroid review leaves open whether lower antibodies translate into delayed hypothyroidism. 3
Does selenium improve the chance of having a baby?
The cited review assessed sperm quality; it does not establish a live-birth benefit. 4
Is the European upper limit a supplement dose?
No. The 255 µg adult limit includes food and supplements together. 5
Should I use Brazil nuts as a supplement?
DGE flags their radium content and advises particular groups to avoid them; they are not a straightforward daily supplement substitute. 6
Related nutrients
Zinc
SelenocysteineSources
- Selenium: Fact Sheet for Health Professionals NIH Office of Dietary Supplements
- Does selenium supplementation prevent hypothyroidism in Hashimoto’s Thyroiditis? American Thyroid Association, 2024
- Scientific opinion on the tolerable upper intake level for selenium EFSA Journal, 2023
- Ausgewählte Fragen und Antworten zu Selen Deutsche Gesellschaft für Ernährung
