Remember the old advice to eat carrots so you could see in the dark? Evidence is mounting that antioxidant nutrients found in many plant foods, including carrots, other red and yellow fruits and vegetables, fish oils and organ meats, may help prevent problems with eyesight that are often associated with aging.

In the EU, around 760 per 100, 000 people are visually impaired. The two major causes of visual impairment in Western countries are cataracts and age-related macular degeneration (AMD) and both of these conditions are associated with diabetes, obesity and advancing age. While visual impairment is not directly life threatening, failing sight can cause serious restrictions on independence, mobility and quality of life.

Oxidative damage is a major risk factor in both conditions. There is increasing evidence that the antioxidant nutrients, particularly vitamins A, C and E, along with the carotenoid pigments, lutein and zeaxanthin, (found in fruits and vegetables), may help prevent or delay the onset of these forms of blindness in old age.

Cataracts

Cataracts are characterised by a clouding of the eye lens, which is made of water and protein and is normally transparent. The lens is found behind the coloured part of the eye-the iris-and it focuses light rays onto the macular at the back of the retina. As cataracts develop, some of the protein clumps together, causing the lens to fog up and preventing light rays from passing through.

For most people, cataracts develop slowly over time with vision gradually becoming impaired. Fortunately, treatment for cataracts is a relatively simple surgical procedure, and involves replacing the opaque lens by an injectable lens implant.

It is unclear what causes cataracts however there appears to be a connection between changes in the chemical composition of the lens with aging. As part of their normal function, body cells, including those in the eye, produce substances called free radicals. Over time, free radicals can damage tissues and organs and it is thought they may be associated with conditions found in aging such as cataracts.

Age-related macular degeneration

Age-related macular degeneration (AMD) is a chronic progressive disease that occurs when the tissue in the macula (the central part of the retina) deteriorates. The macula is the size of a pinhead and is responsible for what we see straight ahead of us and for our sharpest vision, which is necessary for reading, writing, driving at night and our ability to see colour. In AMD, this central vision becomes blurred, straight lines become wavy and colours hard to distinguish. As macular degeneration is a gradual, painless loss of vision that is largely untreatable, it is important to do everything possible to prevent it.

Researchers are uncertain as to why AMD occurs. Aging and a family history are two of the main risk factors. Other factors that may be associated with an increased risk include:

• long term exposure to sunlight
• low blood levels of minerals and antioxidant vitamins such as vitamins A, C and E
• cigarette smoking
• certain circulatory problems such as high blood pressure

Eat more fruits and vegetables

Antioxidant research supports the hypothesis that higher intakes of vitamins C and E may help prevent or delay the development of some cataracts and AMD. More recently, studies have been undertaken on two pigments, lutein and zeaxanthin - that are found in high concentrations in the retina. Lutein and zeaxanthin are found in vegetables such as maize and spinach and in egg yolk. It is thought that high blood levels of lutein and zeaxanthin may protect the retina from damaging wavelengths of light.

As with so many other chronic conditions, the prevention of cataracts and age-related macular degeneration is linked to a healthful diet. The advice to try to get at least five servings of fruits and vegetables daily is as sound advice for healthy vision as it is for many other diseases. So grab some fruit and vegetables and start munching!

LOOKING AFTER YOUR EYES

To keep your eyes in the best of health, the following guidelines can be recommended:

• Eat a healthful diet containing plenty of fruits and vegetables. Choose deep green and dark yellow fruits and vegetables. Vegetables from the cabbage family, including cauliflower, brussel sprouts and broccoli, are also good choices. Lutein and zeaxanthin are found in high levels in egg yolks, maize and spinach.

• Wear sunglasses to protect the eyes from damaging rays
• Control other diseases that increase the risk of degenerative eye disease such as high blood pressure.
• Don't smoke
• Get regular eye check-ups.

   

Eat those carrots

It appears that the traditional advice to eat plenty of carrots to see well in the dark was right after all. Carrots contain beta-carotene, which is converted into vitamin A by the body. In the retina, a form of vitamin A serves as the light-gathering part of the visual pigments and an early sign of deficiency is impaired adaptation to low-intensity light (night blindness). Because the macular pigment is made up of components of dietary origin, eating more plant foods including fruits, spinach, broccoli and maize or supplements containing the antioxidant nutrients beta-carotene and lutein may improve vision and colour perception throughout life and reduce the risk of visual loss in old age.

References

• Eureye Study into Visual Disability due to AMD. Study Coordinator, Professor Fletcher, London School of Hygiene and Tropical Medicine (due to report in 2003)  
• Seddon, J. M.; Ajani, U. A.; Sperduto, R. D. et al. (1994) Dietary carotenoids, vitamins A, C and E, and advanced age-related macular degeneration. Journal of the American Medical Association 272 1413-1420
   

FOOD TODAY 02/2002