People often say carrots help you see in the dark. This is half true. Your eyes need vitamin A to see in dim light. Carrots have beta-carotene, which your body changes into vitamin A. If you do not get enough vitamin A, you cannot see well at night.

But if you already get enough, eating more carrots will not help. The story became famous in Britain during World War II.

The idea that carrots help you see in the dark is only half true. In the retina, a pigment called rhodopsin detects dim light, and it is made partly from vitamin A. American scientist George Wald explained how this pigment works and won a Nobel Prize in 1967.

Without enough vitamin A, people develop night blindness. Carrots contain beta-carotene, which the body turns into vitamin A, so carrots help people who lack it. However, if you already get enough vitamin A, extra carrots will not improve your night vision. The myth is often said to have spread in Britain during World War II.

Telling children that carrots help them see in the dark contains a grain of truth. Night vision depends on rod cells in the retina, which detect light using a pigment called rhodopsin. George Wald, who received a Nobel Prize in 1967, showed that rhodopsin combines a protein with a compound made from vitamin A and changes shape when it absorbs light, triggering a visual signal.

Without enough vitamin A, the body cannot make sufficient rhodopsin, leading to night blindness, and the deficiency remains a major cause of childhood blindness where nutrition is poor. Because carrots are rich in beta-carotene, which the body converts into vitamin A, they help those who are deficient. For people with enough vitamin A, however, eating more carrots does not sharpen night vision, as eye specialists point out.

Why, then, did the myth become so popular? A widely told story holds that during World War II, Britain credited the success of its night-fighter pilots to carrots in order to hide its new airborne radar. Historians, however, debate how deliberate this deception was, since Britain was also encouraging people to eat home-grown carrots during wartime rationing.