mineral · for hair thinning
Selenium
Your thyroid needs selenium, and thyroid trouble is a known cause of hair loss.
Say that in clinical terms
Required for thyroid hormone synthesis and conversion of T4 to T3. Selenoprotein P supports hair follicle growth.
How strong is the research?
A case report found selenium supplements were the probable cause of hair loss and nail damage.
2 papers read, 1 against.
Who was studied: An observational study linking selenium levels to hair loss in women — not a trial of taking it.
How much to take
daily
50–100 mcg
Deficiency impairs thyroid function. Avoid exceeding 200 mcg/day without testing.
Before you take it
- NIH ODS Tolerable Upper Intake Level (UL) for selenium is 400 mcg/day for all adults (ages 14+); EFSA (2023) set a more conservative UL of 255 mcg/day for all adults based on evidence linking chronic excess intake to hair loss and nail changes.
- The primary clinical signs of chronically high selenium intake (selenosis) are hair loss and nail brittleness or loss; NIH ODS explicitly names these as the most common manifestations of selenium toxicity, not deficiency.
- Average US dietary selenium intake is approximately 100–150 mcg/day; supplemental doses of 100–200 mcg/day may approach or exceed the EFSA UL (255 mcg/day) in individuals with higher dietary selenium from food or geography, without the user being aware.
- Individuals in high-selenium geographic regions (parts of the US Great Plains — South Dakota, Nebraska, Wyoming) may have dietary intakes near or above the NIH UL before any supplementation is added.
- Drug interaction: cisplatin and platinum-based chemotherapy agents reduce selenium concentrations in hair and serum; selenium supplementation during chemotherapy may affect cisplatin efficacy; patients on these agents must consult their oncologist before supplementing.
- Selenium form substantially affects bioavailability and tissue retention: selenomethionine (organic) is retained longer and accumulates more in tissues than sodium selenite (inorganic) or selenium-enriched yeast; the same supplemental dose carries meaningfully different toxicity profiles depending on the form.
- In thyroid patients on levothyroxine, selenium is a cofactor for iodothyronine deiodinase enzymes that convert T4 to active T3; supplementation may alter thyroid hormone metabolism and should be disclosed to the prescribing clinician.
- Selenium supplementation above the RDA (55 mcg/day) is not recommended during pregnancy without confirmed deficiency; excessive selenium is teratogenic in animal models.
- A 2008 US outbreak documented 201 individuals developing alopecia, nail changes, and neurological symptoms from a commercial selenium-containing supplement; the product contained approximately 200 times its labeled selenium amount, demonstrating the real-world toxicity risk from over-the-counter selenium products.
- NIH ODS explicitly names hair loss as the primary manifestation of excessive selenium intake (selenosis); recommending selenium supplementation for hair thinning without first confirming selenium deficiency via serum testing creates direct risk of worsening the presenting symptom rather than alleviating it.
- Serum selenium measurement is clinically indicated before any supplementation when hair thinning is the presenting complaint because the direction of the selenium-hair relationship depends entirely on whether the patient is deficient or already replete or excess.
When to take it
Best taken: with food
What we make of it
The citation is a letter about retinoids and depression.
The detail
The identifier resolves to a real article, but it is a correspondence letter replying to a discussion about oral retinoids and depression. It has nothing to do with selenium or hair.