Iron Status and Longevity: Why Too Little and Too Much Both Carry Risks
Iron is essential, but both too little and too much cause harm. Hepcidin, a hormone made by the liver, is the central regulator of the body's iron balance, and its disruption underlies both iron overload and some anaemias.2 Here is what ferritin tests can and cannot tell you, and what the evidence shows about lowering iron.
- Iron is essential but highly toxic when unbound; a 2014 analysis argued that much of the ferritin in blood leaks from damaged cells, so ferritin reflects cell damage and inflammation as well as iron stores.3
- WHO recommends ferritin for diagnosing iron deficiency in otherwise healthy people; with infection or inflammation, below 70 µg/L may indicate deficiency in adults, and above 150 µg/L in menstruating women or 200 µg/L in men and other women may indicate a risk of iron overload.1
- In a cohort of 31,192 people of northern European descent, iron-overload-related disease developed in 28.4% of men but only 1.2% of women who carried two copies of the C282Y hemochromatosis variant.4
- Higher ferritin is linked to type 2 diabetes: in a 2012 meta-analysis, people with the highest ferritin had a 63% higher risk after adjusting for inflammation, an association rather than proof of cause.7
- Blood donors have had fewer heart events in observational studies, but in a randomized trial of 1,277 people with artery disease, lowering iron by regular blood removal did not reduce deaths or heart attacks and strokes.5,6
Iron is essential for carrying oxygen and producing energy, but unbound iron is highly toxic, which is why the body binds and stores it carefully. A 2014 analysis argued that much of the ferritin found in blood is released from damaged cells, which would explain why serum ferritin correlates with markers of cell damage and hydroxyl radical formation as well as with body iron stores.3
Iron Physiology: The Hepcidin Regulator
Hepcidin, a hormone made by the liver, is the central regulator of the body's iron balance. Too little hepcidin causes the iron overload of hereditary hemochromatosis and some other conditions, while too much is associated with the anaemia of inflammation, chronic kidney disease and a form of iron deficiency anaemia that resists treatment.2
A critical feature of human iron biology: there is no regulated iron excretion pathway. Iron leaves the body only through blood loss (menstruation, donation, bleeding), skin cell shedding, and very small amounts in bile and urine. This means that dietary iron absorption must be precisely matched to losses — and that any imbalance that persists for years to decades produces progressive iron accumulation or iron depletion.
Ferritin, Inflammation and Disease Risk
Ferritin is the standard test of iron stores, but it needs careful reading. WHO guidance says ferritin is a good marker of iron stores and should be used to diagnose iron deficiency in otherwise healthy people; in adults with infection or inflammation, a ferritin below 70 µg/L may indicate iron deficiency, and a ferritin above 150 µg/L in menstruating women or 200 µg/L in men and non-menstruating women who are otherwise healthy as a possible risk of iron overload.1 Because ferritin also rises with inflammation and cell damage, a high value is not always a sign of excess iron.3
Higher iron stores are linked to type 2 diabetes. In a 2012 meta-analysis of prospective studies, people with the highest ferritin levels had a 70% higher risk of type 2 diabetes than those with the lowest, or 63% higher after adjusting for inflammatory markers, and a high intake of heme iron was also linked to higher risk.7 These are associations and do not prove that iron causes diabetes.
Hereditary Hemochromatosis: The Genetic Extreme
Hereditary hemochromatosis, most often caused by inheriting two copies of the HFE C282Y variant, leads to iron overload through a lack of hepcidin.2 In the Melbourne Collaborative Cohort Study of 31,192 people of northern European descent aged 40 to 69, followed for an average of 12 years, documented iron-overload-related disease, such as cirrhosis, liver fibrosis or liver cancer, occurred in 28.4% of male C282Y homozygotes and 1.2% of female homozygotes.4
Does Lowering Iron Help?
The idea that lower iron protects the heart is known as the iron hypothesis. In a Nebraska cohort, 655 blood donors reported fewer cardiovascular events than 3,200 non-donors (crude odds ratio 0.50), but the benefit was confined to non-smoking men, and the groups differed in education, physical activity and diabetes.5 When iron reduction was tested in a randomized trial, removing blood every six months in 1,277 veterans with peripheral artery disease did not significantly reduce all-cause mortality or the combination of death, heart attack and stroke.6 Blood donation is valuable for others, but the evidence does not show that lowering iron extends life.
Put this research into practice: Biomarker Reference Tool · What Should I Test Next?
References
- 1World Health Organization. "WHO guideline on use of ferritin concentrations to assess iron status in individuals and populations." 2020. who.int (checked 2026-10-01).
- 2Nemeth E, Ganz T. "The role of hepcidin in iron metabolism." Acta Haematol. 2009;122(2-3):78-86. PubMed · DOI
- 3Kell DB, Pretorius E. "Serum ferritin is an important inflammatory disease marker, as it is mainly a leakage product from damaged cells." Metallomics. 2014;6(4):748-73. PubMed · DOI
- 4Allen KJ, et al. "Iron-overload-related disease in HFE hereditary hemochromatosis." N Engl J Med. 2008;358(3):221-30. PubMed · DOI
- 5Meyers DG, et al. "Possible association of a reduction in cardiovascular events with blood donation." Heart. 1997;78(2):188-93. PubMed · DOI
- 6Zacharski LR, et al. "Reduction of iron stores and cardiovascular outcomes in patients with peripheral arterial disease: a randomized controlled trial." JAMA. 2007;297(6):603-10. PubMed · DOI
- 7Bao W, et al. "Dietary iron intake, body iron stores, and the risk of type 2 diabetes: a systematic review and meta-analysis." BMC Med. 2012;10:119. PubMed · DOI
