Beneficial Nutrients for Eye Health

15 Sep 2019

Let’s explore nutrient-rich food sources scientifically proven to be beneficial for our eye health, including vitamins A, E, and C, zinc, beta-carotene, lycopene, lutein, zeaxanthin, and other molecules with antioxidant properties.

Vitamin A and Its Significance for Vision Physiology

It is known that vitamin A plays a crucial role in visual physiology. To maintain good eye health, it’s essential to obtain an adequate amount of vitamin A through our diet. The rod cells in the retina are sensitive to vitamin A deficiency. Rod cells are responsible for our ability to see in dim light and for the rapid adjustment of our eyes to darkness. Studies have shown negative results in night vision threshold tests in individuals with low serum vitamin A levels. Prolonged vitamin A deficiency can lead to severe eye dryness, affecting vision in the cornea and conjunctiva. Animal-based sources rich in vitamin A include liver, fish oil, and egg yolk. Fatty fish such as salmon, tuna, and mackerel are especially rich in vitamin A and contain omega-3 fatty acids, which exhibit antioxidant properties.

Additionally, some of the carotenoids found in vegetables and fruits can be converted into vitamin A in the body. Analyzed carotenoids include alpha-carotene, beta-carotene, and gamma-carotene. Carotenoids are pigments responsible for the red, yellow, and orange colors in vegetables and fruits. Carrot, red pepper, mango, apricot, red grape, kiwi, and pumpkin are rich sources of beta-carotene. Some vegetables, although green in color due to the suppression of carotenoids by chlorophyll, are also rich in carotenoids. For example, broccoli and spinach, while green, are considered carotenoid-rich foods.

Lycopene has the highest degree of saturation with oxygen among carotenoids. Lycopene is a potent antioxidant, and foods such as tomatoes and watermelon are rich sources of lycopene.

Lutein and Zeaxanthin: Non-Vitamin A Carotenoids

Lutein and zeaxanthin are carotenoids that do not exhibit vitamin A activity. These carotenoids are predominantly found in plant-based sources. Vegetables like spinach, parsley, curly kale, broccoli, purslane, corn, and fruits like cantaloupe and oranges are abundant sources of lutein and zeaxanthin. These compounds act as potent antioxidants and are primarily found in the retina layer at the back of the eye. The retina layer experiences elevated oxidative stress due to light exposure, and lutein and zeaxanthin protect cells in the macula and retina from oxidative damage. Egg yolk is also a significant source of lutein and zeaxanthin from animal origin.

Vitamin E: Another Antioxidant

Vitamin E, like vitamins A and carotenoids, acts as an antioxidant. It exerts a protective effect at the cellular level by reducing oxidative damage caused by free radicals. Plant-based oils such as sunflower, corn, and soybean, as well as nuts like almonds, peanuts, and hazelnuts, are rich in vitamin E. Selenium, a mineral with antioxidant activity, works more effectively in the presence of vitamin E. Selenium is more prevalent in animal-based foods, including red and white meat, seafood, liver, and other organ meats.

Vitamin C: The Water-Soluble Antioxidant

Vitamin C is a water-soluble vitamin known for its antioxidant activity. Its advantage over other antioxidants is its ability to exhibit antioxidant effects in bodily fluids. Citrus fruits, green vegetables, rose hips, kiwi, tomatoes, and strawberries are rich sources of vitamin C.

Zinc: A Mineral for Eye Health

Zinc is a mineral found in abundance in muscles, liver, kidneys, and the retinal layer of the eye. It acts as an antioxidant by aiding the function of enzymes that reduce oxidative damage. Shellfish, especially oysters, are rich in zinc. Beef is also a source of zinc, while dairy products, though in lower amounts, contain this mineral. High consumption of fiber-rich foods can reduce serum zinc levels due to the binding of zinc by phytates in fibrous foods.

The Role of Antioxidants in Eye Health

Excess oxidative damage is known to accelerate the development of cataracts in adults. Consuming a diet rich in antioxidants is believed to slow down the formation of adult cataracts by protecting the lens from oxidative stress. Studies have also shown that the use of antioxidants can slow down the progression of senile macular degeneration (SMD), a retinal disease that typically occurs in old age.

Resveratrol: A Powerful Antioxidant

Resveratrol is a potent antioxidant that has gained attention in recent years. Red grape skins and seeds, as well as peanuts, are rich sources of resveratrol. It plays a crucial role in reducing oxidative damage and preventing premature cell aging.

Omega-3 Fatty Acids: Essential for Eye Health

Omega-3 fatty acids are molecules known for their antioxidant activity. They are essential, meaning they cannot be synthesized in the body and must be obtained through diet. DHA, an omega-3 fatty acid, is found in high amounts in the retina. It is believed to play a role in reducing oxidative stress in the retina. Additionally, recent studies have shown a connection between dry eye syndrome and omega-3 deficiency. Fatty, cold-water fish such as salmon, tuna, and mackerel are rich sources of omega-3. Among them, salmon stands out as an excellent source.