Eyesight and nutrition
Visual function whose maintenance depends on specific nutrients, notably vitamin A for night vision and the carotenoids lutein and zeaxanthin for protecting the retina.
Eyesight relies on very well-identified nutrients, which makes it one of the areas where the link between diet and function is best established. Vitamin A plays the central role: in the form of retinal, it is part of the pigment in the rods, the cells responsible for vision in low light.
This explains the first sign of deficiency: night blindness, difficulty seeing in dim light. Worldwide, vitamin A deficiency remains a major cause of preventable blindness in children.
Lutein and zeaxanthin are the retina’s specific nutrients. This is the least well-known point: these two carotenoids concentrate selectively in the macula, where they filter blue light and limit oxidative damage. They are found mainly in dark green vegetables (spinach, kale, broccoli), egg yolk and sweetcorn, and not in carrots, which have the reputation wrongly.
Carrots provide beta-carotene, a precursor of vitamin A: they help meet needs, but do not improve the eyesight of someone who already gets enough. The idea that they sharpen night vision in adults comes from a British disinformation campaign in the Second World War, designed to hide the use of radar.