Many people think spinach has a lot of iron. In fact, it has about the same amount as other leafy vegetables. Also, our body cannot take in iron from plants very well.

There is a famous story that a scientist made a mistake with a decimal point, so the number became ten times too big. But a researcher checked this story and found no proof for it. The story was a myth, too!

Thanks to the cartoon character Popeye, spinach became famous as a vegetable full of iron. In reality, raw spinach has about 2 mg of iron per 100 g, which is not much more than other leafy greens. In addition, iron from plants is harder for the body to absorb than iron from meat and fish, and spinach contains oxalic acid, which is thought to block absorption even more.

For years, people explained the myth with a famous story: an early scientist put a decimal point in the wrong place, making the value ten times too high. However, in 2014 a Norwegian researcher traced the story back and found that it had no reliable source. A story about checking your sources had never been checked itself.

Spinach owes much of its reputation as an iron-rich superfood to Popeye, yet the nutritional facts are modest. Raw spinach contains roughly 2 mg of iron per 100 g, a respectable amount for a vegetable but not exceptional among leafy greens.

Also, a review of iron bioavailability explains that the non-heme iron found in plants is absorbed less efficiently than the heme iron in meat and fish, and that absorption depends strongly on other foods eaten at the same time: vitamin C enhances it, while phytic acid, calcium and tea polyphenols inhibit it. Spinach is also high in oxalic acid, which is thought to bind iron. The myth's supposed origin is even more revealing.

In 1981, a hematologist wrote in the BMJ that an early analysis had recorded spinach's iron content ten times too high because of a misplaced decimal point. The tale became a popular illustration of scientific skepticism. However, when the Norwegian researcher Rekdal traced its origins in 2014, he found that the original article cited no source and that no primary evidence of the error could be located. He called it an "academic urban legend," showing how claims can spread through citation without anyone verifying them.