Cast iron is the universally recommended "buy it for life" pan. Bare iron with seasoning. No coating to fail, no enamel chemistry, no synthetic compounds. The honest qualification is hemochromatosis — a hereditary iron-overload condition that's more common than most people realize.
Iron leaching is real and modest
Alves et al. (2019, systematic review, PLOS One) — iron-containing cookware increased the iron content of foods and modestly improved hemoglobin in children in low- and middle-income settings. Effect size in adult women of reproductive age: smaller and inconsistent (28.6% of studies showed significant improvement).
Geerligs et al. (2003, PMID: 12859709) — earlier review supporting cast-iron pots as a complement (not replacement) to iron supplementation in iron-deficiency anemia trials.
Adish et al. 1999 — Ethiopia trial: spaghetti sauce iron rose from 0.6 → 5.7 mg per 100 g after cast-iron cooking. Statistically significant hemoglobin rise in the intervention group.
Hereditary hemochromatosis — the risk subgroup
Adams et al. (2005, NEJM, PMID: 15846235) — C282Y homozygote prevalence in non-Hispanic whites in the U.S.: 0.44%. Roughly 1 in 227 Americans carry the homozygous genotype. Many are undiagnosed.
Milman 2021 (PMC8110241) — standard clinical guidance: hemochromatosis patients should avoid uncoated cast-iron cookware, particularly with acidic foods. Carbon steel falls into the same category.
If iron-overload runs in your family, ask your doctor about HFE genotyping before committing to a cast-iron-primary kitchen. The condition is treatable with phlebotomy but requires diagnosis.
Plain-language summary
Most people benefit slightly from cooking in cast iron. About 1 in 227 should avoid it. If you've never had a ferritin test, get one — it's cheap, and it changes the answer to "should I cook in cast iron" from a guess to a number.
Seasoning chemistry — what actually works
Cast-iron seasoning is fat polymerization. Drying oils with high alpha-linolenic acid (ALA) content cross-link most aggressively: flaxseed oil (57% ALA) > canola (10%) > most other seed oils.
Canter 2010 popularized flaxseed-oil seasoning on the chemistry argument. The real-world catch: flaxseed produces the hardest polymerized layer in lab conditions but is brittle and prone to flaking with sustained kitchen use. Refined high-smoke-point oils (canola, grapeseed) and animal fats produce more durable seasoning with repeated cooking — multiple thin layers polymerized at 450–500°F.
Common myths debunked
- "You can't use soap on cast iron." Mild soap is fine. The myth predates modern dish detergents that contained lye. Modern soaps don't strip seasoning.
- "You can't cook tomato sauce in cast iron." Brief cooking is fine. Hours-long simmer of acidic foods will strip seasoning and leach more iron — relevant for hemochromatosis carriers, not for healthy cooks.
- "Rust ruins a pan." Wrong. Surface rust scrubs off with steel wool. Re-season and continue.
- "Pre-seasoned Lodge is fully ready out of the box." Closer to true today than ten years ago, but a few seasoning rounds at home still produces a better surface.
Carbon steel vs. cast iron
Same iron-leach behavior. Same seasoning chemistry. Carbon steel is lighter, heats faster, and has a smoother surface; cast iron retains heat better and is cheaper. Both belong in the SAFEST tier. Pick by feel.