Kale, Collards And Spinach Beat Carrots For Protecting Aging Eyes
When you hit 40, you know reading glasses are not far behind. But as you pass 50 and 60, age-related eye diseases become a much bigger worry. Age-related macular degeneration (ARMD) is the leading cause of blindness for people 65 and older, while cataracts contribute to nearly half of blindness worldwide.
Researchers don't know for sure what causes either of these sight saboteurs, but they do know that older age, light-colored eyes, smoking and exposure to sunlight increase a person's risk. Researchers speculate that oxidative damage may be the crux of the problem and, thus, may hold the solution. For ARMD, that's critical, because unlike cataracts, for which surgery is available, treatment options for ARMD are few.
Age-Related Macular Degeneration
Can anything stave off ARMD, which occurs when macular cells in the center of the retina deteriorate? One clue: The retina is rich in fatty substances, making it susceptible to oxidation.
Lutein and Zeaxanthin. Researchers at the National Eye Institute found that people with higher intakes of antioxidant carotenoids--particularly betacarotene, lutein and zeaxanthin--have less risk of ARMD. When they narrowed the foods that provided apparent defense, dark green leafy vegetables were found to offer a degree of protection carrots couldn't muster.
They then zeroed in on lutein and zeaxanthin, found in dark greens like kale and spinach, because these two carotenoids are concentrated in the yellowish macular pigment of the retina. As antioxidants, lutein and zeaxanthin help defend the retina against free radicals plus help maintain blood vessels in the macula. They also filter out blue light, which researchers believe is the most damaging to eyesight.
Consider recent evidence. Two separate studies show that eating foods rich in lutein can increase macular pigment. The Eye Disease Case-Control Study found that those with the highest blood levels of lutein and zeaxanthin were 70% less likely to develop ARMD than those with the lowest levels. And people who ate spinach and collard greens five or more times a week (averaging 6 milligrams of lutein a day) had 43% less risk of ARMD than those who consumed the greens less than once a month. Moreover, the Nurses' Health Study found that eating spinach more than five days a week lowered risk by 47%.
Some research suggests that other antioxidants, notably vitamins C and E, may be needed for lutein and zeaxanthin to effectively protect the retina.
Glutathione. Paul Sternberg, M.D., professor of ophthalmology at Emory University School of Medicine in Atlanta, is currently researching another powerful antioxidant, glutathione. Certain compounds in fruit, especially apples, have been shown to boost levels of glutathione in the retina. Now, Sternberg is studying whether oral glutathione supplements can prevent retinal damage.
Cataracts occur when the protein portion of the lens clumps together and clouds small areas of the lens, interfering with vision. Researchers believe this results from oxidative damage.
Vitamin C. Researchers from San Francisco reviewed government surveys and found that people with high blood levels of vitamin C were much less likely to have cataracts. Another study showed that people who took C supplements for 10 years or more had 77% fewer "early" cataracts and 83% fewer moderate cataracts.
Vitamin E. Studies have found fewer cataracts in people with high blood levels of vitamin E as well as in those who take E supplements--in one study, the risk was cut in half. However, not all research has been as positive.
Carotenoids. Just as leafy greens are thought to help fend off ARMD, they also may guard against cataracts. The Nurses' Health Study found that women eating cooked spinach more than twice a week had about one-third fewer cataracts needing surgery than those who ate spinach less than once a month.
Weight. The weight gain that often accompanies aging may be a risk factor for cataracts, perhaps because of a link to high blood pressure. Data from the Physicians' Health Study found that those with a Body Mass Index (BMI)-a measure of body weight compared to height--of nearly 28 and above were 25% more likely to develop cataracts than those with a BMI under 22.
Eye on Supplements. Should you take supplements marketed to protect your eyes, such as ICaps by Alcan Labs? No, says the National Eye Institute (NEI). Although researchers have linked foods rich in lutein and zeaxanthin to healthy eyes, the NEI cautions there's little evidence that supplemental lutein can reduce the risk of ARMD or cataracts.
"Whether supplements can improve eye health has not yet been shown," says Emily Y. Chew, M.D., deputy director of epidemiology and clinical research at NEI. "We don't yet know if [supplemental] lutein has adverse effects." Other substances found with lutein and zeaxanthin in foods may play roles just as important; isolating only two carotenoids may not be wise.
As for other supplements, Chew is currently heading the Age-Related Eye Disease Study, a 10-year trial of 5,000 older men and women testing whether the development of ARMD or cataracts is slowed by supplemental antioxidants (vitamins C and E, beta-carotene, selenium and zinc, plus copper to prevent zinc deficiency). Results of the study are due out this year. Other research shows that simply taking a multivitamin can reduce cataract risk by one-third. And vitamin E supplements might cut risk even more.
EN's Bottom Line. For now, food sources are your best bet for eye-protective antioxidants. For one, lutein and zeaxanthin are found in the macula in a ratio similar to that found in foods. Moreover, some research suggests that lutein is most effective when accompanied by other antioxidants, as naturally occurs in fruits and vegetables. Most important, almost all the research to date has linked disease prevention to foods, not supplements. EN advises focusing on these sight-saving tips:
Eat dark green vegetables and other lutein-rich foods every day (see chart, above).
Eat two servings of fruit every day.
Consume at least two rich sources of vitamin C every day, especially citrus fruits and juices, kiwi, sweet and hot peppers, strawberries, broccoli, papaya, cantaloupe and kale, plus a moderately rich source like Brussels sprouts, mango, cauliflower, tomatoes, cabbage and potatoes.
Incorporate vitamin E-rich foods, like wheat germ, seeds and nuts (especially almonds, peanuts, pistachios and walnuts) into daily menus. Consider a natural vitamin E supplement (100 to 400 IU a day).
Take a daily multivitamin/mineral.
Maintain a desirable weight.
Shade your eyes with sunglasses and a hat whenever you are in the sun.
Looking for Lutein
Foods Lutein and
Kale, 1/2 cup cooked 10.3
Collard greens, 1/2 cup cooked 6.9
Spinach, 1/2 cup cooked 6.7
Turnip greens, 1/2 cup cooked 6.1
Spinach, 1 cup raw, chopped 6.0
Cornmeal, yellow, 1 cup uncooked 1.9
Broccoli, 1/2 cup cooked 1.7
Corn kernels, 1/2 cup cooked 1.5
Zucchini, 1/2 cup raw with skin 1.3
Peas, canned, 1/2 cup 1.1
Brussels sprouts, 1/2 cup cooked 1.0
Persimmon, 1 medium 1.4
Orange juice, from concentrate,
8 ounces 0.3
Orange, 1 medium 0.2
Source: USDA-NSS Carotenoid Database of U.S.
Foods, 1998; www.nal.usda.gov/fnic/foodcomp.
By Catherine Golub, M.S., R.D.