"There's a reason why these adages become adages: in large part because they're true," says Taylor. "When you eat a carrot, you're helping your body take a light source [and interpret it]. ... That makes food pretty darn important. That's the stuff that will keep me up at night, it's so exciting."
For eyesight, a carrot's nutritional punch comes from beta carotene, a "carotenoid" the body can convert into vitamin A, according to T. Michael Redmond, chief of the Laboratory of Retinal Cell and Molecular Biology at the National Eye Institute. Vitamin A enables opsin proteins to form in "cone cells" and rhodopsin protein to form in "rod cells" near the back of the eye. Cone cells process light in daytime conditions, while rhodopsin does the same in dim light. When light hits rhodopsin or cone opsins, it creates an electric impulse that travels to the brain for interpretation, helping us see.
Vitamin A deficiency can lead to night blindness, a condition in which people have difficulty adjusting their vision to low levels of light. "You go into a movie theater," Taylor explains, "and you see nothing. You can't process the little bit of light that's in there."
But night blindness is rare in the U.S. because vitamin A deficiency is rare in this country, according to the Centers for Disease Control and Prevention. That may help explain why carrot enthusiasts don't have superior eagle eyes compared with carrot detractors: Even without carrots, most people are getting enough vitamin A from other sources. (Sweet potatoes can provide even more vitamin A than carrots do, and dark leafy greens like spinach and kale are also vitamin A treasure troves.)
Enabling vision is not the same as improving vision. According to the online World Carrot Museum — which exists — the British government began touting carrots' health benefits during World War II to lure consumers away from rationed foods. Part of that campaign emphasized vitamin A's role in seeing in the dark. From the campaign, the myth grew that carrots improved already-healthy vision in the dark — for example, during blackouts. That claim is false, according to Harvard Health Publications.
"Vitamin A will [help] keep your vision healthy; it won't improve your vision," Taylor says. "It won't keep you from needing glasses or contacts."
There's one more catch to vitamin A's powers. Because vitamin A is a fat-soluble vitamin, one needs to eat it with fat in order to fully absorb it and its benefits. Eating a raw carrot won't deliver as much vitamin A punch. "That's why you need to dip it in ranch," quips Taylor.
Because the process of converting beta carotene to vitamin A is somewhat inefficient, the National Eye Institute's Redmond says it's important to eat orange-colored foods frequently, as well as other foods with vitamin A, like dairy and fish.
To make nourishing the eye easier, Taylor recommends an ideal plate for healthy vision. Most of the plate would be taken up with a spinach and kale salad, red peppers, almonds and carrots on top — good sources of vitamin A, E and C, all of which support eye health. An oily dressing helps with intake of fat-soluble vitamins A and E. (Some hard-boiled eggs would also add carotenoids that protect vision, as well as fat to help absorption.) On the side, kiwi and oranges provide vitamin C, and fish like swordfish or salmon offer zinc, another key ingredient for eye health.
But if that doesn't tickle your fancy, Taylor recommends a favorite from childhood. "I used to grow carrots with my daddy in the garden," Taylor says. "Try roasting carrots, parsnips, beets and fingerling potatoes with olive oil, rosemary and sea salt. ... Life just doesn't get better than that."
Gnawing Questions is a semi-weekly column answering the food mysteries puzzling us and our readers. Got a question you want us to explore? Let us know via our contact form.