During World War II (WWII), emerging technologies were held close to the chests of the side that invented them, from code machines (like the Nazi enigma) to novel weapons. When the British developed a new on-board radar technology for its warplanes, they too wished to keep this nifty bit of kit a secret. The cover-up saw pilots hailed as night-vision superheroes, and as blackouts plunged much of the country into darkness, good vision became a more covetable skill than ever before. The combination of events led to an unexpected mascot for WWII, whose image was plastered across walls and printed in papers: Doctor Carrot.
The secret equipment in question was called Airborne Interception Radar (AI), and it gave the Royal Air Force an advantage in enabling them to detect enemy bomber planes before they reached the English Channel. The tech went into broad circulation in the UK in 1939 and by 1940 pilot John "Cat's Eyes" Cunningham became the first in the RAF to take down an enemy plane aided by the novel technology.
According to the World Carrot Museum's website, before the war, carrots were one of the less popular vegetables growing in English soils. Despite this, its suitability for growing in UK conditions made it the star of a government initiative to keep the country fully stocked with food, and soon there was a surplus of carrots. As such, those in the armed forces were fed a lot of carrots and the UK Government's Food Ministry went so far as to suggest that the RAF's exceptional night-flying success was the result of their bumper serving of carotene, a nutrient which is abundant in carrots. The vision-enhancing skills would've made for a convenient cover story to mask the RAF's secret weapon, but in 1941 the Germans found the AI in the remains of a British plane that made an emergency landing in France, and they swiftly developed a similar system.
However, the night-vision rumors were already out, and in the ration era, carrots underwent something of a rebranding as a vision-enhancing super-food and a source of natural sugars when fun sugars were in short supply. England’s residents were led, quite literally, down the garden path and encouraged to consume them by the bucketload, with many all-vegetable recipes circulating to make the most of this abundant grocery item.
Around this time, the slogan "Carrots keep you healthy and help you see in the blackout" was used extensively. One newspaper entry from the UK Times, 6 February 1942, hosted on the World Carrot Museum’s website reads, “Eye in the Blackout. Some odd, unexpected little talents Doctor Carrot possesses. Not only does he entertain you at mealtimes, giving savour to your sweets and sweetness to your savouries, but he can actually – did you know? – help you to see better in the blackout. Meet Doctor Carrot, you’ll like him.”
This (slightly creepy) introduction to the bespectacled Doctor Carrot boosted the carrot's position in the estimations of UK residents, whose carrot fever was fueled by posters depicting army men whose night-vision was attributed to their diet rich in Vitamin A. Posters urged that a surge in the nutritious food item could make the blackouts – practiced to make it harder for enemy planes to bomb landmarks – more bearable. Quite the starring role, I think you'll agree, for a humble root vegetable.
In truth, eating a surplus of carrots will most likely not noticeably improve your vision. However, getting enough Vitamin A in your diet is important for healthy eyes and a good way to avoid nyctalopia, also known as "night blindness", which is a symptom present in a range of conditions and deficiencies. In some extreme cases, eating too many carrots can actually cause a condition that seems stranger than fiction called carotenemia. The (mostly harmless) condition is often confused for the far more serious condition jaundice, as an overdose of the photosynthetic pigment beta-carotene can literally turn your skin bright orange.
[H/T: World Carrot Museum]