Spinach is a leafy vegetable believed to hold a high iron content, making it a healthy and nutritious food for human consumption. In most media featuring Popeye it is used as a last-minute device in which the hero, in danger, pulls out a can of spinach from his shirt or otherwise acquires the vegetable and eats it. This gives his already formidable strength a greater increase, helping him withstand Bluto's attacks and all kinds of adverse situations.

This did not initially exist in Segar's comic Thimble Theatre, where Popeye originated, later simply becoming the food that Popeye favored in order to remain strong, before seeing more widespread use in post-Segar comics. Since the earliest animated cartoons, however, as produced by Fleischer Studios, it was soon introduced in its strength-boosting capacity and in this form would remain a staple of all of Popeye's animated incarnations.

Due to his promoting the vegetable, Popeye has received honors from the spinach industry, such as the statue erected in Crystal City, Texas (the "Spinach Capitol [sic] of the World" as described on its Popeye-featuring welcome sign) in 1937.

"Popeye" brand spinach (pictured) continues to be sold by the Allen Canning Company.