Your 20/20 diet for eye health

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FOCUS IN ON FOODS AND SUPPLEMENTS THAT MAY KEEP YOUR EYES AND VISION AT THEIR PEAK The tissues of the eye are susceptible to oxidative damage, just like tissues elsewhere in the body

The thought of aging usually makes

us worry about chronic diseases, such as heart disease, cancer, and diabetes, not eye health. Yet, the growing prevalence of age related eye diseases has brought them more into focus, coupled with the fact that a growing body of research points to a simple dietary prescription as a potential way to prevent vision loss.

It makes sense — the tissues of the eyes are susceptible to oxidative damage, just like tissues elsewhere in the body. And sunlight causes oxidative damage to the eye. Studies suggest that a diet rich in nutrients that have antioxidant and anti-inflammatory properties may help offset the potential threat to vision that peroxidation can trigger. That's why experts believe that nutrition plays a vital role in eye health. "It's very important, since it's the only means available to noninvasively delay the progress of age-related eye disease at present," says Alien Taylor, PhD, director of the Laboratory for Nutrition and Vision Research at Tufts University's USDA Human Nutrition Research Center on Aging in Boston.

Here's a look at the some of the most common eye diseases that seem to accompany aging, and what science suggests we can do to head them off.

• AGE-RELATED MACULAR DEGENERATION (AMD), the leading cause of vision loss in people 65 and older, affects more than 10 million Americans. It gradually breaks down the macula (the densest part of the retina that contains your photoreceptors), thereby destroying central vision, which is what allows you to see fine detail for tasks such as reading or driving.

Nutrition Links: The most revealing findings to date have been from the Age-Related Eye Disease Study (AREDS), a study of 4,519 adults, ages 60-80. They indicated that a specific antioxidant plus zinc formula (with vitamin C, vitamin E, beta-carotene, and zinc) was effective at reducing AMD risk. In addition. Harvard researchers recently concluded that "a healthy lifestyle with a diet containing foods rich in antioxidants, particularly lutein and zeaxanthin, as well as omega-3 fatty acids, appears beneficial for AMD and possibly cataracts." Lutein and zeaxanthin are two carotenoids that concentrate in the retina and lens, and one of their key protective functions seems to be helping to block out damaging UV radiation. The duo is found in egg yolks and dark green leafy vegetables. For reducing the risk of cataracts and age-related macular degeneration, a 6-20 mg daily dose of lutein should be consumed through diet or supplements. Although there is not much information on the amount of zeaxanthin to consume, both lutein and zeaxanthin have been shown to be safe when taken in amounts higher than 10 mg for many months.

Other recent findings from a five-year study of more than 2,200 Australian older adults (average age of 64) suggest that consuming omega-3 fatty acids, namely eating three or more portions of oily fish per week, could reduce the risk of developing AMD by as much as 70 percent. Another study of 7,752 adults found that those with the highest vitamin D blood levels had a 40 percent reduction in risk of AMD compared to those with the lowest concentrations. Omega-3 oils should provide 200-500 mg of DHA (docosahexaenoic acid) daily. Up to 2,000 IU of vitamin D can be taken daily.

• GLAUCOMA is one of the leading causes of blindness in the United States and the most common cause of blindness among African-Americans. Marked by damage to the eye's optic nerve, which usually occurs due to increased fluid pressure inside the eye — called intraocular pressure (IOP) — it leads to vision loss and blindness.

Nutrition Links: Some older study findings have suggested that people who develop chronic, open-angle glaucoma (the most common type) may have a decreased ability to absorb thiamine, which may have an adverse effect on cells in the optic nerve. The RDA for thiamine is 1.4 mg daily, but most multiples have 50-100 mg. Chromium deficiency has also been observed in individuals with glaucoma. Chromium is in most multiple vitamins at 200 mcg daily. Other studies suggest that both vitamin C and omega-3 fatty acid intake may reduce the risk of glaucoma by decreasing IOP. Take vitamin C in 500-mg doses two or three times daily.

• CATARACTS are a widespread condition, affecting nearly 20.5 million Americans age 40 and up. By age 80, more than half of all Americans have cataracts. Believed to be precipitated by lifetime UV light exposure, smoking, poor diet, and alcohol consumption, cataracts are a clouding of the lens that usually advances with age.

Nutrition Links: Glutathione (GSH) is highly concentrated in the lens and is believed to act as a free radical scavenger that detoxifies the delicate tissue. GSH levels in the lens seem to drop as we age, which may make the lens increasingly vulnerable to damage. Glutathione is produced from N-acetylcysteine and vitamin C. Higher vitamin C intake in women under 60 years of age has been tied to a lower risk of cataracts, and using vitamin C supplements for 10 years or longer meant a 60 percent risk reduction compared with no supplement use. Besides vitamin C, a number of antioxidants have been studied for cataracts, but the evidence isn't as compelling as it is for AMD. A few that seem promising so far include vitamin C, vitamin E, lutein and zeaxanthin, and multivitamin supplements, but more large-scale studies need to bolster the findings, says Taylor.

• DIABETIC RETINOPATHY is a leading cause of blindness in the United States and in the industrialized world. It's a complication of advanced or poorly controlled diabetes, which is caused by damage to the blood vessels of the retina, and it can lead to blindness. Generally, the longer a person has diabetes, say over 20 years, the more likely that person will develop retinopathy. Advanced retinopathy affects about 1 in 20 people with diabetes. However, controlling blood glucose and blood pressure, and making lifestyle changes has been shown to alter the rate of progression.

Nutrition Links: Lifestyle data from the Diabetes Control and Complications Trial, a study of more than 1,000 patients with type 1 diabetes, demonstrated that following a low-fat diet, as recommended by the American Diabetes Association, which includes keeping saturated fat intake to less than 10 percent of calories and total fat to less than 30 percent of calories, slowed the rate of retinopathy progression by 33.2 percent. Higher dietary fiber reduced it as well, whereas higher overall calorie intake, dietary fat, and cholesterol increased the risk.

Some preliminary animal trials suggest that a mere 2 percent increase in omega-3 fatty acid intake (from food) could cut disease severity in half. The omega-3 fatty acid DHA is highly concentrated in the retina. In addition, when researchers at the University of Wisconsin looked at antioxidants' potentially protective effect, they found that users of vitamin C and E supplements (or multivitamin formulas with them) had a decreased risk of diabetic retinopathy; dietary intake of the same nutrients didn't seem to have a preventive effect, which means Mom was right — take your vitamins !

EAT RIGHT FOR YOUR SIGHT
According to Marc Grossman, OD, a New York-based optometrist and author of Natural Eye Care — An Encyclopedia, a variety of dietary nutrients and herbal supplements can help keep eyes healthy. The following are just some of the dietary daily dosage recommendations for prevention that you can find on his Web site, naturaleyecare.com. NA below denotes not applicable.

Legend for Chart:
A - NUTRIENT/HERB
B - AMD
C - CATARACTS
D - GLAUCOMA
E - DIABETIC RETINOPATHY
A
B C
D E
Beta-carotene
15,000-25,000 IU 15,000-25,000 IU
15,000-25,000 IU NA
Bilberry
240-300 mg 240-300 mg
240-300 mg 240-300 mg
Chromium
200 mcg NA
200 mcg 200 mcg
Lutein
6-20 mg 6-20 mg
NA NA
Magnesium
500 mg NA
500 mg 500 mg
N-acetylcysteine (NAC)
500-1,000 mg 500-1,000 mg
500-1,000 mg NA
Omega-3 fatty acids
1,500 mg NA
1,500 mg NA
Quercetin
1,000 mg 1,000 mg
1,000 mg 1,000 mg
Rutin
300 mg 300 mg
300 mg 300 mg
Selenium
200 mcg 200 mcg
NA 200 mcg
Vitamin C
500-3,000 mg 500-3,000 mg
500-3,000 mg NA
Vitamin E
400-500 IU 400-500 IU
400-500 IU NA
Zeaxanthin
Prevention, 3 mg; therapeutically, up to 20 mg NA
NA NA
Zinc
30 mg 30 mg
30 mg NA
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By Angela Pirisi

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