Selenium
Supplements · Minerals · Supplement, Typed Supps
A trace mineral your thyroid cannot work without.
Stage by stage
- Intake (Tablet): Often bound to an amino acid (selenomethionine) in supplement form, which absorbs efficiently.
- Small intestine (Amino acid transporters): Absorbed via the same transporters used for that amino acid.
- Bloodstream (Circulates): Circulates in the blood before being taken up by tissues that need it.
- Thyroid & antioxidant enzymes (Built into key enzymes): Incorporated into enzymes that both make thyroid hormone and act as antioxidants.
What the evidence supports
- Preventing deficiency disease in low-selenium regions — strong evidence. Supplementation eliminated Keshan disease, a selenium-deficiency cardiomyopathy, in affected parts of China. A genuine public health success.
- Reducing thyroid antibodies in autoimmune thyroiditis — limited evidence. Several small trials show antibody reduction, but whether that translates into better thyroid function or symptoms is unresolved.
- Preventing prostate cancer — insufficient evidence. A large prevention trial found no benefit, and a signal of increased type 2 diabetes risk. The early observational optimism did not hold.
Typical dose
55–200 mcg daily
Upper limit: 400 mcg daily for adults
Timing
With food; consistent daily intake matters more than timing.
Time to effect
- Weeks: Blood levels normalize.
Medication interactions
- Statins and niacin: High-dose antioxidant combinations blunted the HDL response in at least one trial. (moderate)
Common myth
“More selenium boosts immunity further.” In reality: Selenium has a narrower safety margin than most minerals — more isn’t better past adequate intake.
Food sources
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