Iron

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

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 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

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.

Side/Adverse effects

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.

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.