Unfortunately, it turns out that spinach's claim to fame can be attributed to a typo from the 19th century, followed by one of the greatest conspiracies in the history of agriculture.
A 1870 German study that served as the basis for Popeye's spinach-fueled 'roid rage accidentally printed the decimal place for spinach's iron content one spot too far to the right. For our non-mathematically inclined readers, that means the report claimed the vegetable had 10 times its actual amount of iron, which ended up equaling out to almost as much as red meat.
"No thanks, I'll have the compost."
As a result, entire generations of children, adults and doctors grew up thinking that eating spinach would turn you into freaking Wolverine.
Unfortunately, it appears that all the E. Coli scares on the planet won't erase one 140-year-old typo. You thought we were kidding about the spinach industry having a propaganda wing? To this day, the Kids edition of the Encyclopedia Britannica informs children that spinach is "loaded" with iron in the first sentence of its spinach entry, and the abridged version of the Encyclopedia uses three of its 79 word definition to tell us that "spinach is rich in iron." Oddly, Britanica's watermelon entry says nothing about its iron content, even though the fruit has just as much iron as spinach while managing to taste far less like shit.
That is a conspiracy.