Iron

Iron is essential for hemoglobin and many enzymes. Mainstream nutrition focuses on preventing deficiency. Excess stored iron is common in adults and ties to oxidative damage, infection risk, and accelerated aging.

Iron
Iron pipe showing rust (iron oxide)
Chemical formula	Fe
Solubility	Essentially insoluble as the metal; Fe²⁺ and Fe³⁺ salts vary with pH
Bioavailability	Heme iron (meat): roughly 15–35% absorbed. Non-heme iron (plants, fortified foods, supplements): roughly 2–20%. Increased by vitamin C and meat; decreased by phytates, polyphenols (coffee, tea), calcium, and zinc
Dietary sources	Heme: liver, red meat, poultry, fish, shellfish. Many grains and pastas are iron-fortified by law (ferrous sulfate)
RDA (adults 19–50 y)	Men: 8 mg/day; Women (premenopausal): 18 mg/day; Postmenopausal women: 8 mg/day; Pregnancy: 27 mg/day
Upper limit	45 mg/day supplemental/fortified (ages 14+); natural food iron not included in UL
Ray's verdict

Iron is a potentially toxic heavy metal. In excess, it can cause cancer, heart disease, and other illnesses.

— Ray Peat

The harmful effects of iron-produced free radicals are practically indistinguishable from those caused by exposure to X-rays and gamma rays; both accelerate the accumulation of age-pigment and other signs of aging.

— Ray Peat

Dosing

Peat's practical list for lowering iron burden (*Iron's Dangers*):

• Drink coffee with iron-containing meals
• Avoid orange juice (or other high vitamin C drinks) at the same meal as iron-rich food
• Use shellfish (oysters, shrimp) for copper
• Take about 100 mg/day Vitamin E (not at the same time as iron-heavy meals)
• Avoid supplements and fortified foods with added iron (ferrous sulfate, "reduced iron")
• Blood donation lowers stored iron
• Prefer glass or safe stainless steel cookware; acidic food in iron pans adds iron

Aspirin, Progesterone, and lower PUFA appear in Peat's wider writing on iron-driven peroxidation. Peat limits Liver portions for iron load. See Copper, Vitamin C, Zinc.

History

Etymology

The English word "iron" descends from Proto-Germanic roots; the chemical symbol Fe comes from Latin ferrum.

Iron working dates back over 3,000 years, and its widespread adoption for tools and weapons around 1200 BCE marks the start of the Iron Age.

Structure/Chemical properties

Iron (Fe) is a transition metal (atomic number 26). Biological iron is mainly Fe²⁺ or Fe³⁺ in heme, non-heme proteins, and storage forms (ferritin, hemosiderin). Elemental iron is insoluble; absorption depends on the chemical form and meal context.

Function/Mechanism of Action

Heme iron from meat absorbs more efficiently than plant iron. Women absorb more iron than men; pregnancy raises absorption further.

Coffee, when taken with food, strongly inhibits the absorption of iron, so I always try to drink coffee with meat.

— Ray Peat

Vitamin C stimulates the absorption of iron, so it might be a good idea to avoid drinking orange juice at the same meal with iron-rich foods.

— Ray Peat

Do not pair high-vitamin-C drinks (orange juice, many fruit juices) with iron-heavy meals if the goal is to limit iron uptake. Coffee with meat inhibits absorption. Calcium and dairy also reduce uptake (standard nutrition).

A deficiency of copper causes our tissues to retain an excess of iron, so foods such as shrimp and oysters which contain abundant copper should be used regularly.

— Ray Peat

Too much iron blocks copper absorption; low copper lets tissues hold excess iron.

Medical uses/Effects

Iron treats true deficiency anemia (mainstream medicine). Peat's focus is the opposite problem: chronic excess storage with age, linked to infection susceptibility, lipofuscin, and degenerative disease. Many people absorb iron efficiently from fortified grains and meat without needing supplements.

Iron accumulates continuously with age in men; menstruation slows the buildup in women until menopause, after which their curve may climb even faster.

Estrogen raises iron absorption, so women absorb more iron than men from the same meal, and far more during pregnancy.

Blood iron and ferritin rise with inflammation as iron leaks out of stressed cells, so serum values do not show stored iron; hemoglobin at the low end of the normal range is the safer marker to watch.

Progesterone increases hepcidin, the hormone that restrains iron absorption, as do epitiostanol and mifepristone.

Side/Adverse effects

Iron absorption from the gut is tightly controlled, but excretion is limited to losses from skin and gut cells, bleeding, and menstruation, so the body has no regulated way to shed excess iron.

A single oral dose of ferrous sulfate (2 mg/kg) raised growth of E. coli, Salmonella Typhimurium, Yersinia enterocolitica, and Staphylococcus epidermidis in human serum ~4 hours later versus pre-dose; growth tracked transferrin saturation (S. aureus unaffected; ex vivo serum assay, not gut lumen).

Iron is a signal for biofilm building in Pseudomonas aeruginosa. In iron-sufficient medium, mutants unable to take up iron through the pyoverdine system formed thin biofilms like those of the parent strain under low iron (cell culture). Lactoferrin, at concentrations below those that kill or stop growth, chelated iron and kept P. aeruginosa wandering across the surface by twitching motility instead of forming cell clusters and biofilms (cell culture). Once formed, biofilms of reference E. coli, P. aeruginosa, and S. aureus strains often needed 100 to 1,000 times the usual concentration of certain antibiotics, while other antibiotics still worked at the standard MIC (cell culture).

All microorganisms require iron to grow, so limiting the availability of iron will limit their ability to be infective. Our respiratory and digestive membranes secrete two proteins, lactoferrin and transferrin, which have a very high affinity for iron atoms, as well as other germicidal properties, and provide a first defense against infection.

— Ray Peat

Stress hormones can loosen this hold. Adrenaline and noradrenaline bind the iron inside transferrin and lactoferrin and release it, and bacteria then use the freed iron; at drug-level concentrations this made human serum support bacterial growth (cell culture).

Excess iron drives free-radical injury, destroys Vitamin E, and accelerates age pigment and tissue iron retention. High-dose supplements and fortified foods are the main avoidable sources. See Lipid peroxidation, Harm reduction.

Anemia

Anemia is a deficiency of red blood cells or hemoglobin. Standard practice often assumes it means iron deficiency by default; in Ray Peat's view this assumption is frequently wrong and can be harmful.

Anemia does not mean iron deficiency

Iron overload and anemia can coexist, and anemia alone is not evidence of an iron need:

It is possible to have too much iron in the blood while being anemic. Anemia in itself doesn't imply that there is nutritional need for iron.

— Ray Peat

Excess iron can itself cause a form of anemia: iron destroys vitamin E and oxidizes unsaturated fat in red cell membranes, making the cells fragile and prone to premature breakdown (hemolysis).

An excess of iron, by destroying vitamin E and oxidizing the unsaturated fats in red blood cells, can contribute to hemolytic anemia, in which red cells are so fragile that they break down too fast.

— Ray Peat

Iron deficiency anemia does exist, in laboratory settings and with some chronic bleeding, but it should be the last suspected cause of anemia, considered only when specific blood tests show low iron saturation. Even in pregnancy, slightly low hemoglobin does not justify an iron supplement, and it protects against infections and stress.

The real common causes

Thyroid deficiency is the most common cause of anemia in women, ahead of other nutritional deficiencies, and estrogen dilutes the blood, so lower hemoglobin in females is normal. Hypothyroidism may act by lowering body temperature so much that blood production slows, and the role of vitamin E deserves a look before iron pills are given. In a cross-sectional study of thyroid-dysfunction patients in Ethiopia, anemia was common and hypothyroidism was independently associated with it.

Anemia in women is caused most often by a thyroid deficiency, or by various nutritional deficiencies.

— Ray Peat

He also pointed to copper status as a hidden factor: low copper causes tissue to hold onto excess iron rather than using it properly, which he framed as a reason to eat copper-rich foods regularly rather than reach for iron supplements first:

Practice

Investigate thyroid function and copper/vitamin B12 status before assuming iron deficiency; iron supplementation without confirmed deficiency (ferritin, full iron panel) can worsen anemia rather than fix it. See Thyroid, Iron, Vitamin B12.

EPO

Erythropoietin (EPO) is a kidney hormone that stimulates red blood cell production. Low oxygen and kidney disease change levels. Abuse in sport is a separate issue.

Dosing (Erythropoietin)

Clinical dosing is individualized to target hemoglobin, typically starting around 50-100 units/kg subcutaneously two to three times weekly for standard epoetin alfa, with longer-acting agents (darbepoetin) dosed less frequently. Overcorrection carries real risk (see below), so dosing is titrated to the lowest amount that avoids transfusion, not to a maximal hemoglobin target.

History (Erythropoietin)

Etymology (Erythropoietin)

The name combines Greek erythros ("red") with "poietin" ("maker"), describing its role in making red blood cells.

Paul Carnot and Clotilde Deflandre proposed the existence of a blood-borne factor controlling red cell production in 1906, coining the term. Eugene Goldwasser isolated erythropoietin in pure form in 1977, after decades of work, enabling later production of recombinant EPO as a drug.

The existence of a blood-borne factor controlling red blood cell production was proposed in the early 20th century, but erythropoietin itself wasn't isolated in pure form until 1977, from the urine of patients with severe anemia. The gene was cloned in 1985, work that made recombinant EPO (epoetin alfa) commercially available by the late 1980s, the first blockbuster biotechnology drug and a major source of both legitimate medical benefit and endurance-sport doping controversy.

Structure/Chemical properties (Erythropoietin)

Erythropoietin is a glycoprotein of 165 amino acids (about 34 kDa including its carbohydrate side chains), produced mainly by peritubular fibroblast-like cells in the kidney, with a smaller contribution from the liver, particularly before birth.

Function/Mechanism of Action (Erythropoietin)

Falling tissue oxygen levels stabilize the transcription factor HIF (hypoxia-inducible factor), which drives EPO gene expression in the kidney. Circulating EPO then binds receptors on bone marrow erythroid progenitor cells, promoting their survival and maturation into red blood cells. Levels rise with altitude, blood loss, and chronic hypoxia, and fall with kidney failure (the main cause of the anemia seen in chronic kidney disease) and with some hormonal states.

There is some evidence that estrogen slightly suppresses the formation of erythropoietin, the regulator of red blood cell formation, but most evidence indicates that it is estrogen's suppression of the bone marrow itself that accounts for most of the difference.

— Ray Peat

Medical uses/Effects (Erythropoietin)

Recombinant EPO (epoetin alfa, darbepoetin, and related agents) is used clinically to treat anemia from chronic kidney disease, chemotherapy, and some other causes of reduced red cell production. It is also one of the most notorious doping agents in endurance sport, used to raise oxygen-carrying capacity, prompting the biological passport monitoring systems now used in professional cycling and other endurance sports.

Side/Adverse effects (Erythropoietin)

The main serious risk of EPO therapy is overcorrection: raising hemoglobin too high or too fast increases blood viscosity and has been linked to increased cardiovascular events, stroke, and thrombosis in clinical trials, which is why current guidelines target a moderate hemoglobin range rather than normalizing it fully. EPO can also raise blood pressure and, rarely, trigger pure red cell aplasia from antibody formation against the drug.

Hemoglobin

Hemoglobin is the oxygen- and CO2-carrying protein in red blood cells, built around iron-containing heme groups.

Peat's view

The Haldane-Bohr effect describes how oxygen and CO2 destabilize each other's binding to hemoglobin: high oxygen pressure releases CO2 more easily, while low oxygen pressure (high altitude, stormy weather) lets the body retain more CO2. CO2 released in the cells then relaxes blood vessels, prevents edema, eliminates ammonia, and increases the efficiency of oxidative metabolism.