Innate and adaptive immune cell function (selenoprotein-dependent NF-kB and ROS signaling)
Spermatogenesis and male reproductive function
Hair follicle and nail matrix keratin synthesis
Dosage range
US IOM RDA: 55 mcg/day adults (60 mcg/day pregnancy, 70 mcg/day lactation). EFSA NDA Panel AI: 70 mcg/day adults (EFSA Journal 2014;12(10):3846). EFSA NRV (labelling): 55 mcg. Common supplemental doses: 50-200 mcg/day; the NPC trial used 200 mcg/day Se-yeast. US IOM Tolerable Upper Intake Level (UL): 400 mcg/day adults. EFSA UL (SCF 2000, reaffirmed NDA 2023): 300 mcg/day adults. U-shaped dose-response: both deficiency and excess associated with adverse outcomes (Rayman 2012 Lancet review).
Safety notes
Selenium exhibits a narrow therapeutic window. Chronic intakes >400 mcg/day risk selenosis: brittle/loss of hair and nails, garlic-like breath, gastrointestinal disturbances, peripheral neuropathy, and in severe cases hepatic and renal toxicity. The SELECT trial (Lippman 2009 JAMA) found NO benefit of 200 mcg/day selenomethionine for prostate cancer prevention in selenium-replete US men and signaled possible increased risk of type 2 diabetes in baseline-selenium-replete subgroups (Stranges 2007 Ann Intern Med). The NPC trial (Clark 1996 JAMA) primary skin-cancer endpoint was NEGATIVE; secondary total-cancer-mortality signal was hypothesis-generating only and was not confirmed in SELECT. Bioavailability and biological behavior differ markedly by form: Se-yeast and L-selenomethionine incorporate non-specifically into body proteins; sodium selenite/selenate enter the regulated selenoprotein pool more directly. Pregnancy/lactation: stay within RDA. Patients with autoimmune thyroid disease should consult a clinician before high-dose supplementation. Co-administration with high-dose vitamin C may reduce selenite absorption (use selenomethionine form or temporal separation).
Cross-market regulatory status
🇺🇸 FDA
United States (FDA): Selenium has NO authorized Significant Scientific Agreement (SSA) health claim under 21 CFR Part 101 Subpart E. The only FDA-permitted disease-risk claims for selenium are Qualified Health Claims (QHCs) under 21 CFR 101.93, allowed through FDA letters of enforcement discretion. The original 2003 FDA decision letters (Feb 21 and Apr 28, 2003, Wellness Lifestyles/Wellness International petition) granted QHC status to the statement: "Some scientific evidence suggests that consumption of selenium may reduce the risk of certain forms of cancer. However, FDA has determined that this evidence is limited and not conclusive." A subsequent 2009 FDA decision (FDA-2008-Q-0323) added site-specific QHCs for bladder, prostate, and thyroid cancers; following the May 27, 2010 federal court ruling (Alliance for Natural Health v. Sebelius) some disclaimers were shortened. Selenium is also permitted as a nutrient content claim ingredient under 21 CFR 101.54 ("good source" / "excellent source of selenium") when meeting %DV thresholds. All disease-related claims are restricted to dietary supplement labels and must carry the FDA-mandated qualifier. Structure/function claims under DSHEA (21 USC 343(r)(6)) are separately permitted with the standard disclaimer ("This statement has not been evaluated by the FDA. This product is not intended to diagnose, treat, cure, or prevent any disease.") and FDA notification within 30 days of marketing.
🇪🇺 EFSA
European Union (EFSA / Reg 432/2012): Six authorized Article 13(1) function health claims for selenium under Commission Regulation (EU) No 432/2012 (CELEX:32012R0432), Annex — immune function, thyroid function, maintenance of normal hair, maintenance of normal nails, normal spermatogenesis, and protection of cells from oxidative stress. All six share the standard condition: the claim may be used only for food which is at least a source of selenium per the SOURCE OF [VITAMIN/MINERAL] reference in the Annex to Regulation (EC) No 1924/2006 (>=15% NRV per 100 g/mL or per portion; NRV = 55 mcg per Regulation (EU) No 1169/2011 Annex XIII). EFSA NDA Panel underlying opinions: EFSA Journal 2009;7(9):1220 (immune, thyroid, hair, nails, oxidative stress) and EFSA Journal 2010;8(10):1727 (spermatogenesis). Tolerable Upper Intake Level (UL): 300 mcg/day for adults (SCF 2000, reaffirmed by EFSA NDA 2023). No Article 14 disease-risk-reduction claims and no Article 14 children development claims have been authorised for selenium.
🇧🇷 ANVISA
Brasil (ANVISA): Selênio é reconhecido como nutriente essencial e está listado como constituinte autorizado de suplementos alimentares na Instrução Normativa IN 28/2018 (Anexos III/IV — limites mínimos e máximos por dose diária). As alegações funcionais autorizadas (Anexo V) seguem o padrão verbatim oficial "O selênio auxilia ..." e cobrem famílias consistentes com o escopo EFSA: função do sistema imune, função da tireoide, manutenção de cabelos e unhas, espermatogênese e proteção das células contra os radicais livres (antioxidante). Verbatim character-for-character requer consulta direta ao PDF oficial do BVSMS — authorized_claims ANVISA deste card intencionalmente ausentes até confirmação manual via leitura do PDF oficial. RDC 243/2018 (composição/categorização de suplementos), RDC 459/2020 (regras de transição) e Decreto-Lei 986/1969 (rotulagem base) também aplicáveis.
Effect of selenium and vitamin E on risk of prostate cancer and other cancers: the Selenium and Vitamin E Cancer Prevention Trial (SELECT)
SELECT trial · Phase III RCT n=35,533 · NEGATIVE outcome: selenium did NOT reduce prostate cancer incidence in selenium-replete US men · key trial against indiscriminate Se supplementation in replete populations
Effects of selenium supplementation for cancer prevention in patients with carcinoma of the skin. A randomized controlled trial. Nutritional Prevention of Cancer Study Group
NPC trial · multicenter RCT n=1,312 · 200 mcg/d Se-yeast · primary endpoint (skin cancer) NEGATIVE · secondary total-cancer-mortality signal flagged as hypothesis-generating only · seminal but later contradicted by SELECT
Authorized claims · verbatim (7)
Direct quotes from each jurisdiction's framework · never paraphrased · with framework reference and conditions of use.
🇺🇸 FDA · 1 claim
FDA QHC 21 CFR 101.93 (2003 Wellness Intl letter)
Some scientific evidence suggests that consumption of selenium may reduce the risk of certain forms of cancer. However, FDA has determined that this evidence is limited and not conclusive.
Conditions: QHC permitted under FDA enforcement discretion per 21 CFR 101.93 with mandatory FDA-mandated disclaimer language as shown. Permitted only on dietary supplement labels (not conventional foods). Selenium has NO authorized SSA health claim under 21 CFR Part 101 Subpart E.
🇪🇺 EFSA · 6 claims
Reg 432/2012
Selenium contributes to the normal function of the immune system
Conditions: The claim may be used only for food which is at least a source of selenium as referred to in the claim SOURCE OF [NAME OF VITAMIN/S] AND/OR [NAME OF MINERAL/S] as listed in the Annex to Regulation (EC) No 1924/2006.
Reg 432/2012
Selenium contributes to the normal thyroid function
Conditions: The claim may be used only for food which is at least a source of selenium as referred to in the claim SOURCE OF [NAME OF VITAMIN/S] AND/OR [NAME OF MINERAL/S] as listed in the Annex to Regulation (EC) No 1924/2006.
Reg 432/2012
Selenium contributes to the maintenance of normal hair
Conditions: The claim may be used only for food which is at least a source of selenium as referred to in the claim SOURCE OF [NAME OF VITAMIN/S] AND/OR [NAME OF MINERAL/S] as listed in the Annex to Regulation (EC) No 1924/2006.
Reg 432/2012
Selenium contributes to the maintenance of normal nails
Conditions: The claim may be used only for food which is at least a source of selenium as referred to in the claim SOURCE OF [NAME OF VITAMIN/S] AND/OR [NAME OF MINERAL/S] as listed in the Annex to Regulation (EC) No 1924/2006.
Reg 432/2012
Selenium contributes to normal spermatogenesis
Conditions: The claim may be used only for food which is at least a source of selenium as referred to in the claim SOURCE OF [NAME OF VITAMIN/S] AND/OR [NAME OF MINERAL/S] as listed in the Annex to Regulation (EC) No 1924/2006.
Reg 432/2012
Selenium contributes to the protection of cells from oxidative stress
Conditions: The claim may be used only for food which is at least a source of selenium as referred to in the claim SOURCE OF [NAME OF VITAMIN/S] AND/OR [NAME OF MINERAL/S] as listed in the Annex to Regulation (EC) No 1924/2006.
Common use cases
Daily nutritional support for normal immune function
Antioxidant support for protection of cells from oxidative stress
Support for normal thyroid function (especially in selenium-low soil regions)
Hair and nail maintenance support
Male reproductive health (spermatogenesis support)
Co-factor in comprehensive multinutrient longevity blends
