Eyes are the window to the world. We start abusing our eyes from a very early age both by reading in low light, by rubbing them to get relief from irritation caused by pollutants Nutritional deficiencies can lead to eye diseases such as Xerophthalmia (Vitamin A deficiency) and nutritional optic neuropathy. Poor nutrition is also a leading cause for cataracts and age-related macular degeneration. Good nutrition thus helps in preventing and retarding progression of several diseases.
Nutrients are classified as essential or non essential. Nutrients that are manufactured in the body and do not need to be obtained from food are called as Non essential nutrients . Examples include cholesterol which is present in all animal cells. Essential nutrients must be obtained from food sources, because the body either does not produce them or produces them in amounts too small to maintain growth and health. Essential nutrients include water, carbohydrates, proteins, fats, vitamins, and minerals.
A balanced diet is important for our overall health and therefore may also be helping to keep our eyes as healthy as they can be. How your diet may affect your eye condition depends a lot on the eye condition you have been diagnosed with.
Vitamin A: The most important vitamin for vision
Vitamin A is essential for healthy vision. It is also essential for immunity and maintenance of mucous membranes. Deficiency leads to poor vision and increased possibility of respiratory, intestinal and genitourinary infections.
Vitamin A deficiency can occur for three major reasons:
- Reduced intake of foods rich in vitamin A
- Poor intestinal absorption of vitamin A, usually because of diarrhoea
- Increased need for vitamin A, as occurs during infections, especially measles, herpes simplex, malaria.
Foods rich in vitamin A are as follows:
- palm oil
- dark green leafy vegetables
- sweet potatoes
- coloured fruits like papaya, mango, carrots
Coloured fruits contain beta carotene, which is a source of vitamin A.
Cataract is the clouding of the eye’s lens. The lens is a the important part of the eyes, which helps to bend light rays and focus them on the retina.
Non-modifiable risk factors to the lens are as follows:
- increasing age
- family history
Modifiable risk factors are as follows:
- exposure to sunlight
- diseases such as diabetes
- poor nutrition
Higher intake of carbohydrates and higher dietary glycemic index (dGI) are associated with higher incidence of nuclear and cortical cataracts. The lens has a natural antioxidant called gluthathione. Studies have shown antioxidants have a significant role in preventing and are also thought to slow the progression of cataracts. These include vitamins C, E, carotenoids such as lutein and zeaxanthin. Those with the highest intake of lutein and zeaxanthin had significantly lower risk of developing cataracts. Lutein and zeaxanthin are pigments found within the eye in the lens, retina and macular. They help to prevent the effects of UV radiation.
Sources for vitamin E include
- corn oil
- sunflower seeds
Sources of vitamin C include
- green pepper
Source of lutein and zeaxanthin include:
- dark green leafy vegetables
Glutathione (found in asparagus) has been found to be beneficial in delaying progression of cataracts.
Age-related macular degeneration
This is the most common cause of irreversible blindness in the developed world in people above 50 years of age. Age related Eye Disease study (AREDS) showed that a combination of high levels of antioxidant vitamins A, C and E (in combination with the mineral zinc) significantly reduces the risk of advanced macular degeneration and its associated visual loss.
Recommended doses are
- Vitamin C – 500 mg
- Vitamin E - 400 IU
- Vitamin A (as beta-carotene) -15 mg
- Zinc (as zinc oxide) - 80 mg
- Copper (as cupric oxide) - 2 mg
Lutein is also found to be protective.
People who had diets rich in green leafy vegetables had reduced risk of developing AMD.
Being overweight is known to be a significant risk factor for developing type 2 diabetes. 80 percent of people with diabetes are overweight when they are diagnosed. Maintaining a healthy weight can reduce your risk of developing type 2 diabetes.
Diabetes can affect your eyes in a number of ways. Changing levels of blood sugar (glucose) can cause your vision to become temporarily blurry and in the longer term, this can cause you to develop cataracts earlier.
Good diabetic control maintained with the following steps can reduce your risk
- controlling your blood sugar (glucose levels)
- tightly controlling your blood pressure
- controlling your cholesterol levels
At the moment there is no evidence that taking nutritional supplements such as vitamins and micronutrients can prevent diabetes or complications related to diabetes from developing or progressing.
Dry Eyes is a common condition where there may be a problem with your tears that usually keep your eyes comfortable and moist. Clinical trials have shown that omega 3, a group of fatty acids that we get from our diets, can have a positive effect on the symptoms of dry eye when taken in certain quantities.
Omega 3 fatty acids are also helpful in treatment of dry eyes and prevention of cataracts. People who smoke should not take supplements containing beta carotene as this has been associated with a higher risk of lung cancer. Natural sources of beta carotene do not seem to confer increased risk.
Omega 3 can be obtained from our diet by eating oily fish such as anchovies, herring, mackerel, salmon, sardines, trout, herring and fresh tuna. The NHS recommends that we eat at least two portions of fish a week, including one of oily fish. If you do not eat fish you can also get omega 3 by eating flaxseed/linseed or rapeseed oils and soya foods such as tofu, as well as walnuts and eggs enriched with added omega 3.
It also important to cut down on added sugar in your diet. Added sugar is found in items such as cakes, fizzy drinks, chocolate and other sweet foods such as pastries and jam. There can also be hidden sugar added to some pre-prepared savoury foods such as pasta sauces and baked beans. You do not need to cut down on the natural sugars found in foods like fruit and milk.
Vitamin B complex deficiency can lead to optic atrophy through demyelination of the nerves. Treatment includes cessation of alcohol intake, cigarette smoking and parenteral injections of hydroxocobalamin (vitamin B12) weekly.
Foods rich in vitamin B complex include
- cereals like corn and millet
In a nutshell a healthy diet for the eyes includes
- Vitamin A: cod liver oil, liver, carrots, sweet potatoes, palm oil.
- Lutein and zeaxanthin: dark green vegetables, egg yolk, corn, mango, spinach, lettuce,
- Vitamin C: oranges, strawberries, broccoli, citrus fruits, tomatoes, cherries, grapes.
- Vitamin E: peanuts, almonds, hazelnuts, sunflower seeds.
- Selenium (an antioxidant):yeast, seafood.
- Zinc: oysters, wheat, nuts.
- Omega 3 Fatty acids: cold-water fish (salmon, mackerel, trout)
It is recommended that we take five servings of fruits and vegetables every day, two servings of nuts every day and to eat fish at least two days a week for healthy eyes.
The author is an eye doctor at Aravind Eye Care.