What do the states mean?+
- Solid: well studied, and it works.
- Half-there: the science is still forming.
- A ghost: almost no real studies.
- Hollow: well studied, and it does not work.
- A cord: the pair itself has been tested together.
- Air: nobody has ever tested this pair.
The full scoring method: How we score
Selenium benefits: where the science stands
For thyroid: yes.
Thyroid is what most people take selenium for, and the strongest evidence says it helps (a combined review covering 35 trials). As of August 2026, the verdicts on this page rest on evidence from 47 trials, drawn from the strongest research among the 4,182 papers on PubMed that mention selenium. Every claim is checked below.
4,182 papers on PubMed · evidence from 47 trials
Claim by claim
- ThyroidWell studied, and it works. The biggest review covered 35 trials.
- Cancer preventionWell studied, and it does not work. The biggest review covered 5 trials.
- JointsThe science is still forming. Results lean positive, but there is not much yet.
Pairs people ask about
The three sources we read
- 2018Meta-analysis · pools 5 trials, 21,860 people · no clear effect on cancer preventionsource
- 2024Meta-analysis · pools 35 trials, 2,358 people · moderate benefit for thyroidsource
- 2025Meta-analysis · pools 7 trials, 367 people · moderate benefit for jointssource
Chosen as the strongest evidence out of 4,182 papers on PubMed. Every row links to its paper.
Fair questions
Does selenium work?+
For thyroid, yes. The biggest review covered 35 trials.
Is selenium safe?+
No caution is recorded on this page. That is not a safety guarantee; the studies we read were not safety trials.
Why only 3 sources, when PubMed lists 4,182?+
The 4,182 is every paper that mentions selenium in any way: animal studies, blood measurements, papers where it is a side note. The strongest sources are combined reviews, and each one already gathers every trial its authors could find. Our 3 cover 47 trials between them, and every one is linked above. Both counts are measured, not estimated.