Selenium
Both deficiency and excess cause hair loss; supplementation in adequately-fed adults has no AGA benefit.
How Selenium works — and how well we know it
Cofactor for glutathione peroxidase and other antioxidant enzymes. Both deficiency and excess can cause hair loss; selenium toxicity (selenosis) presents with hair loss as a feature.
oral
55 mcg/day (RDA). Toxicity above ~400 mcg/day chronically.
Trace mineral. RDA 55 mcg/day. Narrow therapeutic window — toxic above ~400 mcg/day.
Patients with documented deficiency.
Evidence distribution across 1 claims
Why the grade is F. Deficiency is rare; excess is the more common AGA-relevant issue (selenosis causes hair loss). No AGA RCT support for supplementation.
Every claim, traced back to its source
We took every major claim made about Selenium and matched it to the specific experimental model behind it. Click a claim to see the model, the finding, and our assessment of how much weight it deserves.
1 claims · evidence-by-evidence breakdown
1Open-LabelWeight: HighSelenium toxicity (selenosis) causes hair lossHair loss is a symptom of selenium *excess*, not just deficiency. Mega-doses in supplement bundles are a real risk.
Case reports and series of selenium overdose, typically from contaminated supplements or mining environments.
Chronic selenium intake above ~400 mcg/day produces selenosis — characterized by hair loss, nail brittleness, GI symptoms, and neuropathy.
Real risk that's more concerning than the (rare) deficiency. Some hair supplements bundle selenium without regard to the user's existing intake.
- Yang G, Yin S, Zhou R, Gu L, Yan B, Liu Y (1989). J Trace Elem Electrolytes Health Dis PMID 2535619
What's still missing from the science
- RCT of selenium supplementation for AGA.
Our verdict on Selenium
Not in our formulary yet
We don't carry this ingredient. We only formulate around actives where the evidence — and the safety profile — is strong enough to recommend with confidence. As the data matures, we may revisit.
Related treatments
How does Selenium stack up against its closest peers?
A genuine cause of reversible hair shedding in iron-deficient patients — but useless and potentially harmful if your iron stores are normal.
Read the breakdown →A botanical 5-alpha reductase inhibitor whose only high-quality trials (in BPH) showed no benefit over placebo; the positive AGA data are small and low-quality.
Read the breakdown →One small Malaysian RCT showed a hair-count increase. Never replicated. Used by Nutrafol to justify its tocotrienol content.
Read the breakdown →