If you have low levels of iron in the blood, you might have received the advice to eat more spinach as a meat-free method for raising your iron levels.
But here’s the truth: spinach doesn’t have much more iron than other leafy greens like broccoli and Brussels sprouts. One cup of raw spinach has .81 milligrams of iron, while the same amount of broccoli has .66 mg. Kale has .24 mg, and brussels sprouts have 1.2 mg per cup, even more than the cup of raw spinach.
There’s even some evidence that spinach might inhibit iron absorption.
“Simply put, spinach should not at all be the first food choice of those suffering from iron deficiency,” Ole Bjørn Rekdal, a researcher who analysed how the spinach myth spread over decades wrote.
But the story of why the idea remains that spinach is an especially good source of iron is filled with myths and misconceptions.
Here’s how it reportedly went down
As the story goes, in 1870, a German chemist named Erich von Wolf was researching the nutritional benefits of spinach. In his notes, he accidentally printed the decimal point in the vegetable’s iron content in the wrong spot. Wolf accidentally increased the vegetable’s iron level to 10 times the actual amount — 3.5 grams of iron suddenly became 35 grams, an extremely high amount of iron.
“Popeye became so popular with children in the 1930s that sales of spinach spiked dramatically across the US,” Michael Aushenker, a Popeye-enthusiast and editor of The Argonaut wrote in 2014.
In fact, spinach growers credited Popeye with a 33% increase in U.S. spinach consumption and saving the spinach industry in the 1930s, according to Popeye’s official website. One brand, Allens Vegetables, still uses the cleft-chinned character to sell its canned spinach.
Researchers recognised the fumble in 1937 and tried to correct it, but Popeye had already debuted four years earlier. The myth perpetuated in the comic stuck. People started to spread the idea that spinach contains just as much iron as red meat. Even today, many doctors tell their anemic patients to bulk up on the vegetable.
Finally, in 1981, Terry Hamblin, a hematology consultant at the Royal Victoria Hospital, spoke out about the typo in the BMJ, documenting the story of how spinach was discovered as a key source of iron in the 1980s — and how in the 1930s, researchers reportedly discovered that a typo had made the amount of iron in spinach ten-times more than it actually was.
But when Rekdal tried to find the original source of the decimal typo, he couldn’t find it. “Nothing indicates that the decimal point error ever was made, but the account about it will most likely live a long and colourful life, just like its parent myth, the belief that spinach is a good source of iron,” he wrote.
Long story short: eat leafy green veggies, which have varying amounts of iron. Just don’t expect any Popeye-level strength to occur. And if you’re looking to increase your iron intake, here are some options.
Christina Sterbenz contributed to an earlier version of this article.