Selenium

Selenium is a trace mineral your body uses to build selenoproteins. These enzymes run thyroid hormone activation. They protect cells from oxidative damage. They support immune defence and reproductive tissue.^[1] The thyroid stores more selenium per gram than any other organ in your body.

If you have heard selenium matters for thyroid health, hair or fertility, this page covers which form absorbs best, how much you need and what the research shows.

Forms of selenium

Selenium in supplements comes as inorganic salts or as organic amino-acid forms. The form changes how well your body absorbs it and how it is stored.

L-selenomethionine is selenium built into the amino acid methionine. Your body absorbs more than 90% of an oral dose. Once inside, selenomethionine slots into proteins wherever methionine is used. This builds a tissue reserve your body can draw on later. It is the form used in nōuxx Green Glow.^[1]

Selenium yeast is yeast grown on a selenium-rich medium. It is mostly selenomethionine plus a mix of other selenium compounds. Bioavailability is high. Composition can vary between batches.^[6]

Sodium selenite and sodium selenate are inorganic salts. They are absorbed less efficiently than the organic forms. They do not build the same tissue reserve. A 2025 bioavailability study found that selenomethionine raised tissue selenium and selenoenzyme activity more reliably than sodium selenite at the same dose.^[6]

How much you need

The European Food Safety Authority sets the adequate intake for selenium at 70 µg per day for adult women. The EU nutrient reference value used on labels is 55 µg.^[1]

Soil selenium varies sharply across Europe. Most of the continent sits on selenium-poor soils. Average intake in many European countries falls below the EFSA reference. The UK, Germany and parts of Eastern Europe routinely test as low. The US Midwest by contrast has high-selenium soil. This is why brazil nuts grown in Brazil can carry 50 to 90 µg in a single nut while a brazil nut from a low-selenium region carries a fraction of that.^[1] Green Glow contributes 45.2 µg per serving. That covers most of a day for a woman whose food sources run low.

The science on women's health

Thyroid

Hashimoto's thyroiditis is the most common cause of hypothyroidism in iodine-sufficient countries. It affects women roughly eight times more often than men. Selenium sits at the centre of the enzymes that activate thyroid hormone and quench the oxidative stress generated during hormone synthesis.^[3]

A 2024 systematic review and meta-analysis in Thyroid pooled 35 randomised trials. Selenium supplementation lowered thyroid peroxidase antibody titres in women with Hashimoto's. It also lowered TSH in patients not yet on thyroid hormone replacement. Adverse events were no different from placebo. The authors graded the evidence as moderate certainty.^[3]

A 2024 network meta-analysis compared selenium against vitamin D and myo-inositol for autoimmune thyroiditis. Selenium was the only single nutrient that reliably reduced both TPO and thyroglobulin antibodies.^[4]

Hair

Selenium is required for the selenoproteins that protect the hair follicle from oxidative damage during the growth phase. Both deficiency and excess are linked to hair loss. The window for benefit sits in the middle.^[5]

A 2024 systematic review in Molecular Nutrition & Food Research looked at micronutrients in androgenetic alopecia. Selenium was one of five nutrients with consistent evidence linking deficiency to hair loss risk. The authors flagged that correcting low status can support hair growth alongside standard treatment. They cautioned against high-dose supplementation in women with already-adequate selenium status.^[5]

A 2023 randomised controlled trial in 83 adults with androgenetic alopecia or telogen effluvium tested an oral supplement containing selenium plus iron and amino acids. The supplement group showed significantly better global assessment scores at 12 weeks than the drug-only group.^[7]

EU authorised health claims

Under EU law, selenium is officially authorised to carry the following health claims:

• Selenium contributes to the normal function of the immune system
• Selenium contributes to the protection of cells from oxidative stress
• Selenium contributes to normal thyroid function
• Selenium contributes to the maintenance of normal hair
• Selenium contributes to the maintenance of normal nails
• Selenium contributes to normal spermatogenesis^[2]

References

[1] National Institutes of Health, Office of Dietary Supplements. Selenium: Fact Sheet for Health Professionals. ods.od.nih.gov/factsheets/Selenium-HealthProfessional

[2] Commission Regulation (EU) No 432/2012 establishing a list of permitted health claims made on foods. Official Journal of the European Union, 25 May 2012. eur-lex.europa.eu

[3] Huwiler VV, Maissen-Abgottspon S, Stanga Z, et al. Selenium supplementation in patients with Hashimoto thyroiditis: a systematic review and meta-analysis of randomized clinical trials. Thyroid 2024;34(3):295-313. doi.org/10.1089/thy.2023.0556

[4] Peng B, Wang W, Gu Q, Wang P, Teng W, Shan Z. Effects of different supplements on Hashimoto's thyroiditis: a systematic review and network meta-analysis. Frontiers in Endocrinology 2024;15:1445878. doi.org/10.3389/fendo.2024.1445878

[5] Wang R, Lin J, Liu Q, Wu W, Wu J, Liu X. Micronutrients and androgenetic alopecia: a systematic review. Molecular Nutrition & Food Research 2024;68(22):e2400652. doi.org/10.1002/mnfr.202400652

[6] Liu G, Cao S, Huang L, et al. Relative bioavailability of selenium yeast, selenomethionine, hydroxyl-selenomethionine and nano-selenium. Frontiers in Veterinary Science 2025;11:1542557. doi.org/10.3389/fvets.2024.1542557

[7] Milani M, Colombo F. Efficacy and tolerability of an oral supplement containing amino acids, iron, selenium, and marine hydrolyzed collagen in subjects with hair loss. Skin Research and Technology 2023;29(6):e13381. doi.org/10.1111/srt.13381