Can carrots help in improving eyesight?
The body uses beta-carotene to make vitamin A, and “vitamin A is really important, there’s no question about that,” says Emily Chew, deputy clinical director at the National Eye Institute. Vitamin A helps the eye convert light into a signal that can be transmitted to the brain, allowing people to see under conditions of low light. 
In addition, the cornea (the clear front of the eye) can literally disappear if the body does not get enough vitamin A. Every year an estimated 250,000 to 500,000 children become blind as a result of vitamin A deficiency. In settings where undernourished people suffer from extreme vitamin A deficiencies, such as Nepal or India, supplements of the vitamin or beta-carotene have been shown to improve night vision. But exactly how many carrots would be needed to optimize night vision remains less clear. Most studies have so far looked at the benefits of beta-carotene or vitamin A supplements, not carrots specifically. One randomized control study in 2005 examined how consumption of roughly 4.5 ounces of cooked carrots six days a week stacked up against other vitamin A–rich options such as fortified rice, amaranth leaf and goat liver for helping address night blindness in pregnant women.
The result: all the foods performed roughly the same, although the vitamin A supplement did best of all. The study found that a regular diet of the cooked carrots for six weeks helped to bring women’s response to darkness to normal levels. (In Western nations about 30 percent of dietary vitamin A comes from beta-carotene but in some developing countries it is the sole source of vitamin A.) Still, other research has shown that beta-carotene does not convert into vitamin A very efficiently—estimates suggest it requires anywhere from 12 to 21 molecules of beta-carotene in the diet to make just one molecule of vitamin A. Beta-carotene, unlike straight vitamin A, would need to be converted in the intestinal wall into vitamin A, meaning most individuals would be better off taking vitamin A supplements, if possible, instead of downing carrots. Binging on carrots would also not improve most Americans’ eyesight. Once you have enough beta-carotene in your body it often will no longer convert to vitamin A, Chew says. The body naturally regulates against excess amounts of vitamin A to prevent accumulation of toxic levels of the substance.
So how many carrots are ideal? “I don’t have any numbers to give you about how many carrots you should eat per day, but everything should be balanced in moderation,” she says. Indeed, if a person eats too many carrots his or her skin may turn a bit orange—a harmless symptom that is not a health concern. Most eye problems stem from vision-impairment caused by issues such as genetics, aging or diabetes that cannot be aided with an infusion of beta-carotene.
