“I’m strong to the finish ‘cuz I eat my spinach.” With those words, Popeye the Sailor inspired generations of kids to suppress their gag reflex and eat all the spinach on their plates. If spinach can give Popeye super strength, it’s worth eating, regardless of whether it tastes good.

The fact is we have all been lied to. For one thing, as originally envisioned, Popeye got his super strength from rubbing a magical chicken, not from chomping on green leaves. More to the point, spinach isn’t nearly as good for you as you might have thought. Popeye and the rest of us think of spinach as a miracle food because of a mathematical error.

The spinach craze started in 1870. German scientist Erich von Wolf conducted research into the iron content of various vegetables. He concluded that spinach has an iron content of 3.5 milligrams per 100-gram serving.

Wolf’s findings were not particularly noteworthy. Although spinach has about 10% more iron than a comparable amount of red meat, it is by no means the powerhouse of veggies. By way of comparison, an equal amount of soybeans yield 8.8 grams of iron.

The problem arose when Wolf published his findings. The decimal point accidentally ended up one spot to the right. Instead of 3.5 mg, his report stated that spinach has an extraordinary 35 mg of iron per serving.

That was all it took to make spinach the superfood for a generation. In 1932, Elzie Segar decided that the fictional sailor he created would get rid of the magical chicken and reach for a leafy green vegetable as the source of super strength. Countless mothers told their sons that they should follow suit if they wanted to have muscles like Popeye’s. Spinach sales immediately increased by 33% throughout the United States.

Wolf’s incorrect numbers were accepted as fact for nearly 70 years. It wasn’t until 1937 — five years after Popeye popularized the spinach craze — that someone spotted the error. By that point, Popeye had become an unwitting co-conspirator in the big lie about spinach.

Sigh…. Yet another childhood fantasy is crushed under the unforgiving weight of reality.