Popeyed at the thought
Everyone knew it was chock-full of the vital vitamins and minerals, particularly iron, which is essential for healthy growth: after all, look what spinach did for Popeye; he could wipe out all-comers and win the adulation of Olive Oyl after he had glugged down a can of spinach.
Some adults have erased and overcome their childhood experience, but others won't ever again allow a mouthful of spinach to pass their lips.