During the Blitz, the British Ministry of Food promoted the idea that carrots dramatically improved night vision. The campaign featured "Doctor Carrot" and suggested that RAF night fighter pilots achieved their success by eating large quantities of carrots. The real purpose was twofold: to encourage civilians to eat the plentiful domestic carrot crop (since imported foods were scarce), and to provide a cover story for the RAF's newly developed airborne interception radar, which was the real reason for improved night fighting success.
The campaign was remarkably effective. Posters proclaimed "Carrots keep you healthy and help you see in the blackout." Recipes for "Carrolade" (carrot lemonade) and carrot fudge circulated widely. The idea that RAF ace John "Cat's Eyes" Cunningham achieved his remarkable night-fighting record through carrot consumption became widely believed.
While carrots do contain beta-carotene (vitamin A), which is necessary for healthy vision, eating extra carrots does not give anyone superhuman night vision. Yet this piece of wartime propaganda has proven so durable that many people still believe it more than 80 years later.