Vitamin A helps convert light energy into nerve energy inside the retina, says Anshel. Without ample vitamin A, the retina struggles to rebuild its rods and cones, specialized cells that respond to light and are essential for vision.
Rods govern peripheral vision and operate in low light, enabling night vision; cones handle central vision, calibrating the color and high-intensity light that come with daytime.
In the retina, vitamin A forms rhodopsin, a light-sensitive protein that responds to light as it enters the eye.
Vitamin A deficiency is the leading cause of preventable blindness in children worldwide, but a milder deficiency may show up as nyctalopia (night blindness) or xerophthalmia (extremely dry eyes).
“The hardest thing we ask our eyes to do is drive at night,” says Anshel. The brightness of oncoming headlights contrasted against the darkness of the road forces the eyes to switch between prioritizing the cones and the rods. Abundant vitamin A makes that job easier.
Most of us get plenty of this nutrient from the beta-carotene — a carotenoid the body turns into vitamin A — in our diets (think carrots). There’s also vitamin A in fish, organ meat, dairy, and eggs. The recommended daily allowance for vitamin A is 700 micrograms for adult women and 900 mcg for adult men.
Too much vitamin A can be harmful, so if you supplement, take care not to exceed 3,000 mcg daily.
→ Best sources: Sweet potatoes, carrots, and liver
→ Most important effect: Prevents night blindness and dry-eye disease
Eating for Eye Health
Food plays a big role in sustaining our vision — and carrots are just the beginning. Discover the best nutrients for eye health at “How to Eat for Eye Health,” from which this article was excerpted.
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