How to eat your way to better eyesight
Two new books on diet and eye health look at the types of food and supplements that can help people with common eye problems ranging from dry eyes to age-related macular degeneration (AMD). AMD affects the macula, the central part of the retina responsible for sharp vision.
Here are some of the conclusions of the books:
ANTIOXIDANTS
Research shows: Antioxidants such as vitamins A, C and E and anthocyanidins – purple blue pigments found in fruit such as blueberries – counteract oxidative stresses, which form harmful “free radicals” that can damage cells and cause diseases.
Antioxidants also have a protective effect on the cells of the retina.
The 2001 Age Related Eye Diseases Study (Areds) in the United States found that high doses of antioxidants, such as beta-carotene, vitamins C and E and zinc, reduced the risk of advanced AMD in patients who were already showing signs of moderate disease.
Beta-carotene is a type of carotenoid – a red, orange or yellow pigment found in fruit and vegetables – which is converted to vitamin A in the body.
These supplements, however, should be taken after seeking a doctor’s advice. For instance, high doses of beta-carotene may increase the risk of lung cancer in smokers or ex-smokers.
Occurs naturally in:
Vitamin A: Carrots, sweet potatoes, pumpkins, cod liver oil.
Vitamin C: Fresh fruit and vegetables.
Vitamin E: Avocados, tomatoes, sweet potatoes, nuts and whole grains.
Anthocyanidins: Eggplants, purple cabbage, purple blue pigments in fruit such as blueberries.
Zinc: Most protein-rich food, shellfish, fish, various meat, dairy products.
LUTEIN AND ZEAXANTHIN
Research shows: Lutein and zeaxanthin are types of carotenoids, which are red, orange and yellow pigments found in many fruit and vegetables.
Lutein and zeaxanthin are compounds found in high concentrations in the retina.
They are good absorbers of excess blue light, which can cause oxidative damage to the retinal cells.
They are also good antioxidants with a protective action effect on the cells of the retina.
Several studies have shown that eating more food or supplements high in lutein and zeaxanthin can increase their levels in the retina.
There are small studies to show that high levels of lutein may reduce the risk of AMD, but more evidence is needed from the ongoing Areds 2, a large multi-centre study similar to the original Areds but with an emphasis on studying the effects of lutein and zeaxanthin on age-related eye diseases.
Occurs naturally in: Egg yolk, corn, dark green leafy vegetables such as spinach and kai lan, squash varieties such as pumpkin and butternut squash.
OMEGA-3 FATTY ACID
Research shows: Omega-3 fatty acid is believed to be good for the eyes because it reduces inflammation and modulates the immune system.
A higher intake of omega-3 fatty acid derived from fish has been linked to a lower risk of AMD.
For patients with AMD, Areds found that higher intakes of omega-3 oil were associated with a lower risk of progression from mild AMD to severe AMD.
This type of oil has also been found to be useful for the condition of dry eye. It reduces the inflammation on the surface of the eye, which inhibits the production of tears in the tear gland.
Omega-3 fatty acid also helps to improve the oily layer of the tears (the meibum) and reduce evaporation of the tears from the surface of the eyes. This, in turn, improves dry eye syndrome.
It is important for omega-3 fatty acid to be in the right balance with the other essential fatty acid called omega-6 fatty acid, which is found in poultry, eggs and various types of vegetable oil.
Both types of oil need to be taken as essential nutrients as the human body cannot make them. They are important parts of the membranes surrounding cells and are also used as chemical messengers involved in processes such as an inflammation.
The recommended ratio of omega-6 to omega-3 is around 5:1 or lower.
Occurs naturally in: Oily fish such as canned tuna, salmon, catfish and sardines.
Plant sources of omega-3 are flaxseed oil, canola oil and safflower oil. But plants are considered a less efficient source of omega-3 fatty acid than oily fish.
Source: Mind Your Body, The Straits Times
Category: Wellness and Complementary Therapies
