The claim: Eating carrots will improve your eyesight.
The facts: The origin of this myth dates back to World War II and is actually based on a bit of truth. Carrots are rich in beta carotene, which the body converts to a form of vitamin A called “retinal,” a key molecule involved in maintaining normal vision.
But unless you are deficient in vitamin A, as from a poor diet, malabsorption problems, or alcoholism, for example, beta carotene (or vitamin A) won’t make bad vision better. As it is, most Americans get enough beta carotene and vitamin A in their diets, though in some developing countries, vision loss due to a lack of these nutrients is much more common.
The notion that carrots improve eyesight can be traced back to the British Royal Air Force during World War II when pilots were using radar for the first time to spot and shoot down enemy planes. According to a source at the Carrot Museum (yes, there is such a place), in an effort to conceal this new “cutting edge” technology, a rumor was started that the pilots ate a lot of carrots, which allowed them to see better at night. The fabricated “fact” stuck and, to this day, we’re told to eat carrots to improve our vision.
While beta carotene won’t give you 20/20 vision, some research has shown that this carotenoid can help some people with age-related macular degeneration (AMD), the leading cause of blindness in people over age 55 in the U.S. The Age Related Eye Disease Study (AREDS), sponsored by the federal government’s National Eye Institute, found that a formula containing high doses of beta carotene, along with vitamins C and E and zinc, reduced progression of intermediate AMD to advanced AMD.
But there are also concerns about taking high-dose beta carotene (it may increase the risk of lung cancer in smokers and possibly previous smokers), which is why the subsequent AREDS2 trial tweaked the original formula, substituting the carotenoids lutein and zeaxanthin for the beta carotene and finding that this combination offered the same, if not better, protection against progression to advanced AMD, than beta carotene.
Less clear is whether beta carotene (or other carotenoids) can reduce the risk of developing AMD in the first place, and what effect carotenoids might have on the development or progression of other eye disorders, such as cataracts. Though the AREDS formula is sometimes promoted for eye health in general, there is no evidence it has any such benefits.
Beyond carrots. The finding of adverse effects from high doses of beta carotene doesn’t diminish the importance of eating foods rich in beta carotene, like carrots, sweet potatoes, papayas, and red peppers, in the context of an overall healthy diet, as one strategy for protecting your eyes. (Note that you can’t get harmful amounts of beta carotene from food sources as you can from beta carotene supplements, which you should avoid.) Your diet should also include good sources of lutein and zeaxanthin (such as egg yolks, corn, zucchini, Brussels sprouts, spinach, and grapes), zinc (as in seafood, meat, dairy products, whole grains, and beans), and healthy fats (as in fish and nuts).
Good sources of vitamin A are dairy foods, eggs, oily fish, and, in limited amounts, liver (but don’t consume more than 5,000 IU of preformed vitamin A a day on a regular basis, and if you take a multivitamin, it should have no more than 3,000 IU of preformed vitamin A, since too much of this vitamin, unlike with beta carotene, is known to harm bones and have other adverse effects).
Also see Are Eggs Bad for Your Heart?