So, "did carrots save Britain by giving pilots superhuman night vision?" Betteridge’s Law of Headlines, named after journalist Ian Betteridge, states: “Any headline which ends in a question mark can be answered by the word ‘no’" (1). That is certainly true in this case, but the question is of historical interest.

In the early days of World War II, the German Luftwaffe (literally, “air weapon”) began a bombing campaign against Britain that came to be known as the Blitz. From September 7, 1940, through May 11, 1941, approximately 40,000 British civilians were killed, frequently during night attacks. In response, Britain ordered blackouts of many cities to obscure potential targets and deployed the Royal Air Force to fight the Luftwaffe in the night skies. Many British fighter pilots became heroes, including John Cunningham (1917-2002), who downed 20 enemy planes – 19 at night – and was said to have extraordinary night vision due to eating many carrots. He earned the nickname “Cat’s Eyes” (2).

Why carrots? The idea that certain foods could prevent or cure night blindness goes back thousands of years. The ancient Greeks recommended eating raw animal liver, which is high in vitamin A, for this purpose (3). Nobel Prize winner George Wald (1906-1997) reported the association of vitamin A with rhodopsin in fish retinas in 1939 (4). The British government encouraged its citizens to eat more carrots to mitigate harmful consequences of the blackouts, including an increase in traffic accidents, and because carrots were abundant and inexpensive, which was important during a period of nationwide food rationing. These efforts included distributing various carrot recipes, as well as a publicity campaign including a 1940 announcement from the Ministry of Agriculture that stated eating more carrots “should overcome the fairly prevalent malady of blackout blindness" (5).

Would feeding large numbers of carrots to normal people improve their night vision? Many foods (liver, some dairy products, eggs) contain vitamin A, but carrots contain beta-carotene, a provitamin A carotenoid that is subsequently converted into vitamin A but with low bioavailability (3, 6). Vitamin A deficiency may cause a spectrum of eye diseases collectively known as xerophthalmia (Greek for “dry eye”), including ocular surface disease, night blindness, retinal changes, and, more rarely, optic neuropathy (7). Supplemental vitamin A is used to treat xerophthalmia, but does not appear to affect the vision of normal subjects and there is no evidence that large doses of vitamin A can grant superhuman night vision.

Some modern historians have written that the story of feeding pilots carrots to improve their night vision was an intentional deception by the British government to hide the presence of a new technology called aircraft interception radar, which was probably more responsible for identifying enemy aircraft in the dark. But whether the Luftwaffe were actually deceived by this claim remains unknown (2).