We’ve almost all grown up with it: carrots are good for your eyesight. And spinach makes you strong (but that’s another story, or is it?). In some places, there’s an even stronger version of the claim: carrots can help you see in the dark. But where does that idea actually come from? And is it true?

Yes, carrots are rich in vitamin A, which plays a role in vision. But most people today already get more than enough of it through a normal diet. Eating extra carrots won’t suddenly improve your eyesight, let alone give you night vision. In fact, too much vitamin A, especially through supplements, can even be harmful.

And this is where it gets interesting. Because this persistent belief isn’t just an innocent piece of folk wisdom. Its roots lie in something far more strategic: World War II propaganda.

During the Blitz, when London and other British cities were being bombed, the British government had good reasons to promote a particular narrative. Through a surprisingly well-designed campaign, they convinced people, both at home and abroad, that eating carrots improved eyesight. And it worked. Perhaps a little too well, because the idea is still with us today.

For this video, Vox set out to trace the origins of the myth. They spoke with an ophthalmologist and a historian of wartime propaganda, and reconstructed how a rather strange campaign managed to have such a lasting impact. And yes, you’ll also meet one of the more peculiar figures of that time: Dr Carrot.