Canned spinach is vile. Popeye was nothing but a shill marketing nasty stuff to gullible kids.
Fresh or even frozen spinach is a thousand times more edible than canned.
That's actually completely accurate. The truth is, spinach isn't all that great. Watermelon as the exact same nutritional value as spinach.
But why does every one believe otherwise? Marketing, of course!
Some federal nutrition board, c. 1910s or so, was compiling nutritional values of various food items to try and set certain food standards. The nutritionist reporting his data regarding spinach,
actually fucked up the math by one digit. Meaning, the official word on spinach was that it contains 10x the iron that it actually contained.
Believing this to be accurate, this was obviously a remarkable discovery. Spinach was suddenly the new superfood and with very little thought, farmers were soon instructed to produce metric shitloads of spinach. There was suddenly, inexplicably, a lot of money invested in spinach. At the same time, this popeye cartoon was quite popular and the spinach lobby found an excellent opportunity to make spinach popular.
The idea became so pervasive, the strategy to overwhelmingly successful, that even after the funny math was corrected and published only some 10? years later, the spinach lobby was too big to stop.