Haemoglobin synthesis (incorporation of Fe2+ into protoporphyrin IX via ferrochelatase to form heme)
Myoglobin synthesis for muscle oxygen storage
Cofactor for cytochrome c oxidase and other respiratory chain Fe-S cluster enzymes (oxidative phosphorylation)
Cofactor for ribonucleotide reductase (DNA synthesis, cell division)
Cofactor for tyrosine hydroxylase and tryptophan hydroxylase (dopamine and serotonin synthesis)
Cofactor for myeloperoxidase and NADPH oxidase in neutrophils (innate immunity)
Hepcidin-ferroportin axis regulates systemic iron homeostasis; high-dose iron raises hepcidin and blunts subsequent absorption
Molecular + tissue targets
Erythropoiesis and haemoglobin
Mitochondrial respiratory chain
Skeletal muscle myoglobin
Central nervous system monoamine synthesis
Innate immune effector cells
Replicating tissues (cell division)
Dosage range
Adult RDA (US): 8 mg/day men and post-menopausal women, 18 mg/day pre-menopausal women, 27 mg/day pregnancy. Tolerable Upper Intake Level (UL, US IOM): 45 mg/day elemental iron from all sources in adults (gastrointestinal tolerance limit). Therapeutic supplementation for iron deficiency: 30-120 mg elemental iron daily or alternate-day; emerging evidence (Stoffel 2017) supports alternate-day single morning dosing to maximize fractional absorption. Pregnancy: WHO recommends 30-60 mg elemental iron daily where anaemia prevalence is high.
Safety notes
Common adverse effects: nausea, epigastric pain, constipation, dark stools (dose-dependent). High single doses raise serum hepcidin and reduce absorption of subsequent doses, supporting alternate-day regimens for non-pregnant adults. Iron overload risk in hereditary haemochromatosis (HFE C282Y homozygotes), transfusion-dependent thalassemia, and other iron-loading disorders — supplementation contraindicated without medical supervision. Pediatric accidental overdose is a leading cause of fatal poisoning in children under 6; keep iron-containing supplements out of reach of children (FDA-mandated warning per 21 CFR 101.17(e)). Iron reduces absorption of levothyroxine, tetracyclines, fluoroquinolones, bisphosphonates, and levodopa — separate by at least 2-4 hours. Calcium, polyphenols (tea, coffee), and phytates inhibit non-heme iron absorption; ascorbic acid enhances it.
Cross-market regulatory status
🇺🇸 FDA
No FDA-authorized Significant Scientific Agreement (SSA) health claim exists for iron under 21 CFR Part 101 Subpart E (the SSA program covers only twelve specified nutrient-disease relationships and iron is not among them). Iron supplements are marketed under DSHEA (Dietary Supplement Health and Education Act of 1994) using structure/function claims (e.g., "supports red blood cell formation", "helps maintain healthy oxygen transport") accompanied by the DSHEA disclaimer "This statement has not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease" per 21 CFR 101.93. Solid-oral-dosage-form dietary supplements containing iron or iron salts must carry the warning statement required by 21 CFR 101.17(e): "WARNING: Accidental overdose of iron-containing products is a leading cause of fatal poisoning in children under 6. Keep this product out of reach of children. In case of accidental overdose, call a doctor or poison control center immediately." The 1997 unit-dose packaging requirement for iron supplements containing 30 mg or more per dose was vacated by the court in Nutritional Health Alliance v. FDA (3d Cir. 2003) and the corresponding regulation was removed by FDA in 68 FR 59714 (October 17, 2003); only the warning-statement portion of 21 CFR 101.17(e) remains in force.
🇪🇺 EFSA
Iron has multiple EU-authorized health claims under Commission Regulation (EU) No 432/2012 establishing the Union list of permitted health claims pursuant to Regulation (EC) No 1924/2006 Article 13(1). All authorized iron claims share a single condition of use: "The claim may be used only for food which is at least a source of iron 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." This corresponds to at least 15% of the Nutrient Reference Value supplied by 100 g/100 mL/per portion. Authorized claim functions: cognitive function, energy-yielding metabolism, formation of red blood cells and haemoglobin, oxygen transport in the body, function of the immune system, reduction of tiredness and fatigue, and role in the process of cell division.
🇧🇷 ANVISA
Iron (ferro) is listed as an authorized constituent of dietary supplements (suplementos alimentares) in Brazil under ANVISA Instrucao Normativa IN 28/2018 Anexos I, III and IV (minimum and maximum daily limits for the population groups defined therein), with complementary labeling rules in RDC 243/2018 and RDC 269/2005 (IDR reference values). Authorized functional claims for iron appear in IN 28/2018 Anexo V (lista de alegacoes autorizadas para uso na rotulagem dos suplementos alimentares); however, in this drafting pass the official Anexo V verbatim text for ferro could NOT be reliably extracted from any reachable official source (the BVSMS PDF and antigo.anvisa.gov.br PDFs returned only binary stream content; the Imprensa Nacional in.gov.br page closed the connection; legisweb and anvisalegis.datalegis.net mirrors truncated the document before Anexo V was reached). Per the NC honest-verbatim rule, no authorized_claims entries are populated for the ANVISA market until successful retrieval of the official Anexo V text in a subsequent editorial pass and the "O ferro auxilia ..." sentences are quoted directly. ANVISA also operates the Programa Nacional de Suplementacao de Ferro (PNSF, Ministerio da Saude) for public-health iron supplementation of children and pregnant women — that program is a public health intervention, not a labeling claim, and is therefore not represented in authorized_claims.
Authorized claims · verbatim (7)
Direct quotes from each jurisdiction's framework · never paraphrased · with framework reference and conditions of use.
🇪🇺 EFSA · 7 claims
Reg 432/2012
Iron contributes to normal cognitive function
Conditions: The claim may be used only for food which is at least a source of iron 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
Iron contributes to normal energy-yielding metabolism
Conditions: The claim may be used only for food which is at least a source of iron 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
Iron contributes to normal formation of red blood cells and haemoglobin
Conditions: The claim may be used only for food which is at least a source of iron 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
Iron contributes to normal oxygen transport in the body
Conditions: The claim may be used only for food which is at least a source of iron 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
Iron 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 iron 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
Iron contributes to the reduction of tiredness and fatigue
Conditions: The claim may be used only for food which is at least a source of iron 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
Iron has a role in the process of cell division
Conditions: The claim may be used only for food which is at least a source of iron 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
Iron-deficiency anaemia treatment
Iron deficiency without anaemia (low ferritin, fatigue)
