Preventing Macular Degeneration Through Nutrition

Macular degeneration (MD) is the leading cause of blindness in the United States. It is often referred to as age-related macular degeneration because the incidence increases with age. MD is caused by deterioration of the macula, the central part of the retina. The retina is the innermost layer of the eye containing receptors for vision called rods and cones, and the macula contains the highest concentration. Early stages of MD can cause visual deficits and advanced stages may result in permanent loss of central vision. Macular degeneration appears to have a genetic component, but studies have shown that diet and nutritional supplements can play prominent roles in prevention and progression of the disease.

In recent years we have learned a lot about vitamin D and its protective effects against osteoporosis, cancer, hypertension, psoriasis and autoimmune disease. We now have reason to believe that it can prevent macular degeneration as well. A study published earlier this year in the Archives of Ophthalmology evaluated data from 7752 people who participated in the third National Health and Nutrition Examination Survey. Those with the highest levels of vitamin D in their blood had a forty percent lower risk of developing MD compared to adults with the lowest levels.

Researchers also analyzed the effects of different sources of vitamin D, including dairy, fish and supplements. Eating dairy products was associated with lower incidence of the early stages of macular degeneration and eating fish was associated with lower incidence of advanced MD. In adults who did not consume dairy products on a daily basis, those who used vitamin D supplements regularly had a lower risk of early MD compared to those who did not take supplements.

Fats also play a key role in the prevention and progression of macular degeneration. Docosahexaenoic acid (DHA), an omega-3 polyunsaturated fatty acid, is one of the healthy fats found in fish. It is particularly important for healthy eyes because it is a major structural component in the outer membrane of the retina. Researchers in Maryland followed 4519 adults between the ages of sixty and eighty and analyzed their dietary intake of omega-3 polyunsaturated fatty acids in fish. They found that those who ate more than two four-ounce servings of fish each week had reduced risk for developing MD.

In another study, researchers in Boston analyzed the diets of 261 adults aged sixty years or older who had already been diagnosed with MD. They found that eating foods rich in omega-3 fats, including fish and nuts, had a protective effect against progression of the disease. They also found that a higher intake of animal fat was associated with a two-fold higher risk of MD progression.

Researchers at the National Institutes of Health have demonstrated the value of antioxidants and carotenoids in the prevention of macular degeneration. Antioxidants, including beta-carotene, vitamin C, vitamin E and zinc, inactivate free radicals that can damage the retina while carotenoids lutein and zeaxanthin accumulate in the macula and absorb ultraviolet radiation.

Although nutrients in supplement form may be helpful in preventing MD and slowing progression of the disease, foods are good sources as well. Beta-carotene is found in kale, spinach and carrots. Vitamin C is concentrated in citrus fruits, green peppers, broccoli, melon, tomatoes and potatoes. Sources of vitamin E include nuts, seeds, soybeans, fish, eggs, leafy green vegetables and wheat germ. Whole grains, beans and other legumes are good sources of zinc. Lutein is found in broccoli and dark green leafy vegetables including kale, spinach, collards and turnip greens. Orange bell peppers, yellow corn, mangoes, carrots, squash, tomatoes, persimmons and dark leafy greens are good sources of zeaxanthin.

Sugar is another important consideration in MD, according to researchers at Tufts University in Boston. They studied the relationship between glycemic index (a measure of the sweetness of foods) and macular degeneration in adults between the ages of fifty-five and eighty and concluded that those who had a higher dietary glycemic index also had a higher risk of MD. In other words, consuming foods that rank high on the dietary glycemic index, such as sugar, flour and processed foods, can increase risk of macular degeneration while whole grains, vegetables and legumes that rank much lower can reduce the risk.

Talk to your doctor before starting any new supplements. To reduce risk of macular degeneration, discuss other modifiable risk factors, including weight, exercise, sun exposure and smoking status. If appropriate, also address conditions that affect blood vessels of the macula, such as high blood pressure, atherosclerosis and diabetes mellitus.