Encyclopedia · supplement
Selenium
An essential mineral with no proof that supplements regrow hair, and a well-known cause of hair loss in excess.
What it is
Selenium is a trace mineral found in Brazil nuts, fish, eggs and meat, and added to many multivitamins and hair blends. Selenium sulfide anti-dandruff shampoo is a different use.
How it works
It is part of antioxidant enzymes and thyroid hormone handling. Too much disrupts thyroid hormone synthesis and damages hair and nails.
What the studies show
- A review found chronic excess affects thyroid hormone synthesis from about 300 micrograms/day, and that nail and hair loss and dermatitis occur at high environmental exposure. Vinceti 2001
- A systematic review of 47 studies placed selenium among the agents with the strongest evidence for causing alopecia on overdose. Yu 2018
- In 90 women with chronic telogen effluvium versus 90 controls, serum selenium was higher, not lower, in the shedding group. Durusu Turkoglu 2024
- A systematic review of 49 articles concluded selenium is involved in pattern hair loss, but evidence is inconsistent. Wang 2024
- A blend with marine collagen, amino acids, iron and selenium added to drugs scored better than drugs alone in 83 people over 12 weeks (1.67 versus 0.66). Selenium's share cannot be separated. Milani 2023
Side effects and safety
The European Food Safety Authority's adult upper limit is 255 micrograms a day. A multivitamin, several hair supplements and Brazil nuts can add up past this, and layering selenium-containing products is the main practical risk.
Bottom line
Meet your needs from food and do not megadose. Selenium toxicity is one of the better-documented nutritional causes of hair loss, so more is not better. Discuss with a doctor.
Fun facts
- Because selenium overdose is a recognised cause of hair loss, a "hair" supplement can backfire. Yu 2018
Studies 5
Vinceti M et al. Adverse health effects of selenium in humans. 2001
Result: Chronic excess affects thyroid hormone synthesis from about 300 micrograms/day; nail and hair loss occur at high exposure.
Read the study ↗Yu V et al. Alopecia and Associated Toxic Agents: A Systematic Review. 2018
Result: Thallium, mercury, selenium and colchicine had the strongest links to hair loss; vitamin A listed among agents with described incidents.
Read the study ↗Durusu Turkoglu IN et al. A comprehensive investigation of biochemical status in patients with telogen effluvium: Analysis of Hb, ferritin, vitamin B12, vitamin D, thyroid function tests, zinc, copper, biotin, and selenium levels. 2024
Result: Only zinc (lower) and selenium (higher) differed; ferritin, B12, vitamin D, biotin and hemoglobin did not.
Read the study ↗Wang R et al. Micronutrients and Androgenetic Alopecia: A Systematic Review. 2024
Result: Deficiencies or imbalances may be modifiable factors but evidence is inconsistent.
Read the study ↗Milani M et al. Efficacy and tolerability of an oral supplement containing amino acids, iron, selenium, and marine hydrolyzed collagen in subjects with hair loss (androgenetic alopecia, AGA or FAGA or telogen effluvium). A prospective, randomized, 3-month, controlled, assessor-blinded study. 2023
Tested: tablet with marine collagen, amino acids, iron and selenium added to drugs vs drugs alone
Result: Global assessment 1.67 vs 0.66; assessor-blinded; contribution of individual ingredients cannot be separated.
Read the study ↗Related
- ZincTrue zinc deficiency causes hair loss that zinc fixes, but zinc has not been shown to regrow hair in people who are not deficient, and too much causes copper deficiency.
- Vitamin AToo much preformed vitamin A can make hair fall out, so extra vitamin A in a hair supplement is more likely to harm than help.
- Hair supplement blends (Nutrafol, Viviscal and similar)Branded multi-ingredient hair vitamins that beat placebo in small, mostly company-linked trials.
- Diet and hairCrash diets and rapid weight loss cause shedding, ordinary diets rarely do, and testing beats guessing before you buy supplements.