Spinach is exceptionally high in iron
Spinach contains a reasonable amount of iron but is not the iron superfood of popular legend. The myth was amplified by a historical data error and the Popeye cartoons, though the cartoons actually attributed Popeye's strength to vitamin A, not iron.
What we know
The legend that spinach is exceptionally high in iron is often traced to a decimal-point error attributed to German scientist Erich von Wolf in 1870, who allegedly recorded spinach as containing 35 mg of iron per 100g rather than the correct 3.5 mg. This story itself has been partially questioned by food historians, who note that the error was corrected in the 1930s but the outsized reputation for iron persisted. Regardless of the precise historical origin, spinach's iron content was overstated in early nutritional literature.
In reality, 100g of raw spinach contains approximately 2.7 mg of iron, which is comparable to other green vegetables and not dramatically higher. Crucially, the iron in spinach is non-heme iron, which is far less bioavailable than the heme iron in meat. Additionally, spinach contains oxalic acid, which binds to iron and further reduces its absorption. Cooking spinach reduces oxalate levels and can improve iron absorption somewhat, but spinach remains a poor source compared to lean red meat or fortified foods.
The Popeye cartoons, often cited as reinforcing the spinach-iron myth, actually had the sailor cite vitamin A rather than iron as early as 1932. The association with strength and iron was an assumption of popular culture rather than a direct message from the cartoons.
Spinach is genuinely nutritious: it is rich in folate, vitamin K, vitamin A from beta-carotene, magnesium, and antioxidants. Its nutritional reputation is well-earned overall, but specifically as an iron source it is less impressive than commonly believed.
Common claims
- Spinach is one of the best dietary sources of iron.Misleading. Its iron is poorly absorbed due to oxalates; meat is far more bioavailable.
- A decimal-point error caused the spinach iron myth.Partly supported. Historical evidence is mixed, but early nutritional data did overstate spinach iron.
- Spinach has no useful nutritional value.False. Spinach is rich in folate, vitamin K, and antioxidants.