Well, in fact the betacarotene in carrots does help with your eyesight, but only if you are deficient in that particular vitamin.  It certainly will not make you see better in the dark for instance.  So where does the myth actually come from?  Well it all started in WWII, with a food shortage and the development of radar.

It actually began in Great Britain during World War II. Lord Woolton, Minister of Food, conducted quite a successful campaign to educate and encourage the civilian population to do all it could to feed itself. At one point they had a glut of…carrots.

In the Battle of Britain, in 1940, the British fighter pilot, John Cunningham, became the first person to shoot down an enemy plane with the help of radar. In fact, in WW II, he was the RAF’s top-scoring night fighter pilot, with a total of 20 kills. Some pilots were better flying in daylight, while others, like Cunningham, were better at night. His nickname was “Cats’ Eyes”. The RAF put out the story in the British newspapers that he, and his fellow night pilots, owed their exceptional night vision to carrots. People believed this to the extent that they started growing and eating more carrots, so that they could better navigate at night during the blackouts that were compulsory during WW II.

The idea stuck and has been perpetuated ever since. Even to this day I still get people talking about improving their visions by eating carrots, particularly when their own children are present. No need to tell children the truth huh?