Ask a Dietitian

As seen on BCTV November 28/00

THE AGING EYE – CATARACTS AND MACULAR DEGENERATION

Cataracts and macular degeneration are among the leading causes of blindness worldwide, particularly among the elderly. Other risk factors include genetics, exposure to sunshine, smoking and diabetes. Cataracts are cloudy areas in the middle or back of the lens of the eye. Oxidative damage from light produces free radicals that can cause cloudiness in the lens. Antioxidants may protect against the oxidative damage by acting as scavengers for the free radicals. The evidence is strongest for vitamins C and E and two carotenoids lutein and zeaxanthin.

Vitamin E is found in the lens, and it can slow the rate at which animals get cataracts. A few studies also found that people with low intakes of vitamin E (from diet or supplement) had higher rates of cataracts. However, the data are inconsistent.

Good sources of vitamin E include nuts, seeds, sunflower oil, whole grains, wheat germ, eggs, margarine and green leafy vegetables.

Levels of vitamin C in the lens are higher than blood levels and vitamin C in the lens can be increase with supplements. In animal studies higher levels of vitamin C protect against lens damage. In humans, more and more evidence suggests that vitamin C protects against cataracts. However, we still don’t know if people who take vitamin C are also getting other nutrients or leading a healthier lifestyle.

Good sources of vitamin C include citrus fruits and juices, papaya, strawberries, melons, berries and other fruits and vegetables.

Lutein and zeaxanthin are also found in large quantities in the lens. These carotenoids absorb ultraviolet light and they are also antioxidants, which may explain how they protect the lens. The results from human studies are more consistent for lutein and zeaxanthin than they are for vitamins C and E.

Best dietary sources of zeaxanthin and lutein in decreasing order include:
Cooked Kale, collard greens, spinach, turnip greens, broccoli, corn and Brussels sprouts. Raw vegetables include romaine lettuce, zucchini, oranges, baby carrots and tomatoes.

Age-Related Macular Degeneration (AMD)
Macular Degeneration is a disease that affects the macula-the central part of the retina that’s involved in seeing fine details and seeing what’s in the center, not around the edges, of your view. Macular degeneration can cause blindness because it ultimately results in the loss of cones in the centre of the macula. The macula is high in polyunsaturated fatty acids, which are susceptible to free radical damage.

Eating high levels of lutein and zeaxanthin might protect against age-related macular degeneration. Zinc is a mineral involved with several enzyme systems that keep the retina healthy and is currently being studied. Some evidence shows that vitamin E may lower the risk of AMD and no studies have shown a link between AMD and vitamin C. One other theory is that inflammation and possibly cardiovascular disease might promote AMD, and omega-3 fatty acids might protect against both. This still needs to be studied further.

Recommendations for prevention of AMD:
Eat more fruits and vegetables, particularly dark green leafy vegetables rich in lutein.

Supplementaion:
Should you take special vitamins for the eyes? No. If you take eye vitamins instead of regular multivitamin-mineral supplements you will miss out on some very important nutrients such as folic acid, B12 and vitamin D. If you take both the multi and the eye vitamin you may get too much of certain nutrients such as zinc, beta-carotene and selenium. You are better off just sticking to your multivitamin-mineral supplement alone.

The Bottom Line:
Eat at least 5 servings of vegetables and fruit each day and emphasize dark green leafy vegetables rich in carotenoids. Reduce saturated and processed fat intake and include good sources of omega-3 fats.

Watch for the Eating for Energy segment every Tuesday on BCTV’s Noon News Hour!