Men Have No Way to Excrete Iron. Does Giving Blood Slow Aging, or Do Healthy Men Just Donate More?
In 1981 a pathologist named Jerome Sullivan wrote a short letter to The Lancet with an unusual explanation for why men get heart disease a decade or more before women. The difference, Sullivan argued, might not be estrogen at all. It might be iron. Premenopausal women lose iron through menstruation and carry small stores; men lose almost none and accumulate it for decades. After menopause, women's iron stores rise and their heart disease rates climb toward men's. Forty-five years later the iron hypothesis is still neither proven nor dead. A Finnish cohort produced striking early support, a large genetic scan in 2020 put iron metabolism among the few pathways tied to human lifespan, and the one serious randomized trial of iron reduction came back mostly null. This article walks through what men should know about their own iron, what ferritin numbers mean, and what blood donation can and cannot be expected to do.
Key Takeaways: What the Research Shows About Iron, Blood Donation and Aging in Men
An adult man carries roughly 1,000 mg of stored iron, about three times the stores of a premenopausal woman, and loses only about 1 mg a day because the human body has no regulated way to excrete iron. In the Kuopio Ischaemic Heart Disease study of Finnish men, a serum ferritin of 200 µg/L or more was linked to 2.2 times the risk of heart attack (Salonen, Circulation, 1992), and donating blood in the previous two years was linked to a relative risk of 0.12 (Salonen, BMJ, 1998). A 2020 genetic study by Timmers and colleagues in Nature Communications, drawing on about 1.75 million people, identified heme and iron metabolism as a pathway linked to lifespan, and Mendelian randomization suggested that genetically higher blood iron shortens healthy lifespan. The FeAST randomized trial of 1,277 patients with peripheral artery disease found that phlebotomy to a ferritin near 25 µg/L did not significantly reduce all-cause death overall (hazard ratio 0.85), though death rates were roughly halved in the youngest quartile, aged 43 to 61. Blood donors are healthier than non-donors before they ever donate, a bias called the healthy donor effect, which explains a large part of the survival advantage seen in donor registries. Men who donate often can become iron deficient. In the HEIRS trial, ferritin had not recovered in most donors 168 days after a single donation unless they took oral iron.
The Finnish Men Who Launched the Iron Hypothesis
Relative risk of acute myocardial infarction in the Kuopio Ischaemic Heart Disease Risk Factor Study of middle-aged Finnish men. Salonen and colleagues reported in Circulation in 1992 that men with serum ferritin of 200 µg/L or more had 2.2 times the heart attack risk. In the BMJ in 1998 the same group reported that men who had donated blood in the previous two years had a relative risk of 0.12, based on a single heart attack among 153 donors. Both are observational findings.
Why do men accumulate iron as they age?
Men accumulate iron because the body absorbs iron from food but has no active pathway to get rid of the excess. Iron leaves the body only passively, through shed skin, gut lining cells and small amounts of blood loss, which adds up to about 1 mg a day in an adult man. A typical Western diet supplies 10 to 20 mg of iron a day, of which the gut absorbs 1 to 2 mg, so a healthy man runs close to balance with a slight tendency to gain. The liver hormone hepcidin controls absorption, lowering it when stores are full, but hepcidin control is imperfect, and red meat supplies heme iron that is absorbed more efficiently than plant iron. The result shows up in population data. Serum ferritin, the standard blood marker of stored iron, rises steeply in men through their twenties and thirties and then plateaus at a higher level. Premenopausal women lose roughly 15 to 30 mg of iron with each menstrual period and through pregnancies, which keeps their stores near 300 mg. After menopause, women's ferritin rises toward men's levels over the following decade.
Men Carry Roughly Three Times the Stored Iron of Premenopausal Women
Approximate iron in milligrams. An adult man typically holds about 1,000 mg of storage iron as ferritin and hemosiderin, against about 300 mg in a premenopausal woman. One 500 mL whole blood donation removes roughly 200 to 250 mg. The body has no active route for excreting iron, so a man loses only about 1 mg a day through shed skin and gut cells.
What is the iron hypothesis of heart disease?
The iron hypothesis proposes that higher body iron stores raise cardiovascular risk, and that the lower iron stores of premenopausal women help explain why they develop heart disease later than men. Jerome Sullivan proposed the idea in The Lancet in 1981. The proposed mechanism is oxidative: free iron catalyses the Fenton reaction, which turns hydrogen peroxide into hydroxyl radicals, among the most reactive molecules in biology. Hydroxyl radicals oxidise LDL cholesterol, and oxidised LDL is the form taken up by macrophages in the artery wall to build plaque. The first strong human support came from eastern Finland, which at the time had some of the highest heart attack rates in the world. In 1992 Jukka Salonen and colleagues reported in Circulation that among 1,931 men in the Kuopio Ischaemic Heart Disease Risk Factor Study, those with serum ferritin of 200 µg/L or higher had 2.2 times the risk of acute myocardial infarction over about three years of follow-up, after adjustment for standard risk factors. In 1998 the same group reported in the BMJ that among 2,682 Kuopio men, 1 of 153 who had donated blood in the previous two years had a heart attack during follow-up, against 316 of 2,529 non-donors, a relative risk of 0.12. The confidence interval around that estimate was wide because it rested on a single event.
What do genetic studies say about iron and lifespan?
Genetic studies give the iron hypothesis its most interesting modern support, because they are less vulnerable to the lifestyle confounding that dogs observational research. In 2020 Paul Timmers and colleagues at the University of Edinburgh published a combined analysis in Nature Communications of three ageing traits: healthspan, parental lifespan and survival to extreme old age, drawing on about 1.75 million people. The analysis identified 10 genomic regions linked to all three traits and found that heme metabolism, the pathway that handles iron in blood, was one of the few biological pathways enriched across them. Mendelian randomization, which uses inherited gene variants as a natural experiment, suggested that genetically higher blood iron levels reduce the number of years lived in good health. The genetic picture is not uniform. Separate Mendelian randomization work by Dipender Gill and colleagues has linked genetically higher iron status to a slightly lower risk of coronary artery disease but a higher risk of certain infections and venous thrombosis, which suggests iron's effects differ by organ system. The clearest genetic evidence comes from hereditary hemochromatosis. Men who inherit two copies of the HFE C282Y variant absorb iron without normal restraint. In UK Biobank, Pilling and colleagues reported in the BMJ in 2019 that male C282Y homozygotes had roughly four times the rate of diagnosed liver disease and higher rates of diabetes, arthritis and frailty than men without the variant, and a 2020 JAMA analysis by Atkins and colleagues found higher all-cause mortality in the same group.
Did the randomized trial of iron reduction work?
The only large randomized trial of iron reduction, the Iron and Atherosclerosis Study, known as FeAST, did not meet its primary goal. Leo Zacharski and colleagues at Veterans Affairs hospitals randomized 1,277 patients with symptomatic peripheral artery disease, almost all of them men, to either usual care or regular phlebotomy aimed at lowering ferritin to about 25 µg/L. The results, published in JAMA in 2007 after a mean follow-up of about 3.5 years, showed a hazard ratio for all-cause death of 0.85 and for the composite of death, non-fatal heart attack and stroke of 0.88. Neither difference was statistically significant. The FeAST investigators had pre-specified an analysis by age, and the youngest quartile, aged 43 to 61 at entry, told a different story. In that group, phlebotomy was associated with a hazard ratio of about 0.46 for death and 0.43 for the composite endpoint. Subgroup findings can arise by chance and need their own trial before they count as evidence, and no such trial has been run. The FeAST result is compatible with iron reduction helping younger men before arterial disease is established, and equally compatible with no real effect.
FeAST: The Only Large Randomized Trial of Iron Reduction Missed Its Main Endpoint
Hazard ratios from the Iron and Atherosclerosis Study (FeAST), Zacharski and colleagues, JAMA 2007. 1,277 patients with peripheral artery disease were randomized to phlebotomy aimed at a ferritin near 25 µg/L or to usual care. Across all ages neither result was statistically significant. In the youngest quartile, aged 43 to 61, both hazard ratios were roughly halved, a subgroup finding that needs confirmation. Values below 1 favour phlebotomy.
Do blood donors live longer?
Blood donors do live longer on average than non-donors, but most of that advantage reflects who is allowed to donate rather than what donation does. Blood services turn away people with heart disease, cancer, infections, anaemia, recent illness and many medications, so the donor population starts out healthier than the general population. Epidemiologists call this the healthy donor effect. People who keep donating for years also have to stay healthy enough to pass screening every time, which strengthens the bias with each donation. Researchers using the Danish and Swedish SCANDAT donor registries have tried to separate the effects by comparing donors with other donors, for example people who donated more often against people who donated less often. Some of those analyses still find lower mortality with more frequent donation, but the frequency of donation is itself tied to health, motivation and income. No randomized trial has assigned healthy men to donate blood or not donate and followed their survival. The Kuopio finding of a relative risk of 0.12 for heart attack sits inside that same limitation.
Can donating blood make a man iron deficient?
Frequent blood donation can make a man iron deficient, and iron deficiency in regular donors is common. One 500 mL whole blood donation removes about 200 to 250 mg of iron, roughly a quarter of a typical man's stores. The HEIRS trial, led by Joseph Kiss and published in JAMA in 2015, followed 215 donors after a single whole blood donation. Donors who took 37.5 mg of elemental iron a day recovered 80 percent of their lost hemoglobin in a mean of 32 days, against 158 days for donors who took no iron. Ferritin returned to baseline in 76 days with iron. Without iron, most donors still had not restored their ferritin by the end of the 168-day study. The standard US interval between whole blood donations is 56 days, which means a man donating at the maximum frequency may never rebuild his stores between visits. Studies of repeat donors in the US and Europe have found low ferritin in a substantial share of frequent male donors, and the Netherlands introduced ferritin testing to manage donor deferral in 2017. For a man whose aim is to lower high iron stores, some depletion is the point. For a man with normal or low stores, iron deficiency brings fatigue, reduced exercise capacity and, in some studies, restless legs.
How Long a Donor Takes to Rebuild Blood and Iron
Days to recovery after one whole blood donation in the HEIRS trial of 215 donors, Kiss and colleagues, JAMA 2015. With 37.5 mg of elemental iron a day, hemoglobin recovered 80 percent of its loss in a mean of 32 days and ferritin returned to baseline in 76 days. Without iron, hemoglobin took 158 days, and most donors had not restored ferritin by the end of the 168-day study, so the grey bar shows a minimum.
- Took oral iron
- No iron
What ferritin level is healthy for a man?
There is no agreed optimal ferritin level for longevity in men, but a range of roughly 50 to 150 µg/L avoids both iron deficiency and the levels flagged in the Kuopio cohort. Ferritin below about 30 µg/L generally indicates depleted iron stores. Many laboratories list an upper limit for men between 300 and 400 µg/L, well above the 200 µg/L threshold that carried excess heart attack risk in the Finnish data. Ferritin has a major flaw as a measure of iron: ferritin is also an acute phase protein that rises with inflammation, infection, heavy alcohol use, obesity and fatty liver disease. A large share of men with high ferritin do not have iron overload at all; they have metabolic disease, sometimes described as dysmetabolic iron overload syndrome. For that reason ferritin should be read alongside transferrin saturation, which measures how much of the blood's iron transport capacity is in use. A ferritin above 300 µg/L combined with a transferrin saturation above 45 percent is the usual threshold for testing the HFE gene for hemochromatosis.
Ferritin Numbers Worth Knowing
Reference points for serum ferritin in micrograms per litre, which is numerically the same as nanograms per millilitre. Iron deficiency is likely below about 30. FeAST lowered patients to about 25. The Kuopio heart attack signal appeared at 200. Many laboratories list an upper male limit near 300 to 400, and a ferritin above 300 with transferrin saturation above 45 percent is the usual trigger to test for hereditary hemochromatosis. Inflammation, alcohol, obesity and fatty liver all raise ferritin without true iron overload.
How does testosterone therapy affect blood and iron?
Testosterone therapy raises hematocrit, the fraction of blood made up of red cells, and it does so partly by suppressing hepcidin, which lets the gut absorb more iron. The effect is dose-dependent and larger with injections than with gels. The Endocrine Society's 2018 guideline advises reducing or pausing testosterone therapy if hematocrit rises above 54 percent, because thicker blood may raise the risk of clots. Many men on testosterone therapy use therapeutic phlebotomy or regular blood donation to keep hematocrit down, and some blood services accept donations from men on prescribed testosterone. Repeated phlebotomy lowers iron stores, which in turn limits red cell production, and men who donate often while on therapy can end up with a normal hematocrit but depleted ferritin. Tracking both hematocrit and ferritin every few months gives a more complete picture than hematocrit alone.
What should a man over 40 take from the iron evidence?
A man over 40 should know his ferritin and transferrin saturation, avoid iron supplements unless a test shows deficiency, and treat blood donation as a reasonable way to manage high stores rather than a proven longevity intervention. Men should not take multivitamins with iron by default, since most men do not need the extra iron and the body cannot remove it. A man with high ferritin should first rule out the common causes that have nothing to do with iron overload, such as fatty liver, heavy drinking and chronic inflammation, and should be tested for hemochromatosis if transferrin saturation is also raised. Hemochromatosis is not rare: roughly 1 in 150 to 1 in 300 people of Northern European ancestry carry two copies of C282Y, and treatment by regular phlebotomy is simple and effective. A man with normal iron who wants to donate blood does real good for patients who need transfusions. The survival benefit to the donor himself remains unproven, and a single well-run randomized trial in healthy middle-aged men would settle a question that has stayed open since 1981.
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