Fending Off Vision Loss: Produce May Have The Power To Protect Your Eyes
If only Mr. Magoo had eaten his vegetables. Perhaps the antioxidants and phytochemicals in those veggies might have helped him keep his vision. It turns out a shopping cart of greens may be the best gift you could give your eyes, short of sunglasses and not smoking, if you want to avoid the consequences that growing older can have on your eyes.
Cataracts and Macular Degeneration. As you age, a lifetime of wear and tear takes its toll on your eyesight. The two most common age-related vision problems are cataracts and macular degeneration.
Cataracts occur when the lens of the eye thickens and becomes inflexible, making focusing difficult if not impossible. The cost of treating cataracts is the biggest item in the Medicare budget; worldwide it ranks as the number one cause of blindness.
Age-related macular degeneration (ARMD) is less well-known, but is the leading cause of irreversible blindness among Americans over 65. ARMD occurs when macular cells in the center of the retina deteriorate. This is caused, in part, by oxidative damage from environmental stress or aging, says Billy R. Hammond Jr., Ph.D., of the University of Georgia, who conducts research on both ARMD and cataracts.
The retina is particularly susceptible to such damage, because it is exposed to the most oxygen of any part of the body. Moreover, the retina contains a high concentration of lipids, easily preyed upon and damaged by oxygen. Researchers believe these "peroxidized" lipids then build up in the retina, creating distortion and eventually loss of vision.
But while cataracts and macular degeneration may be a natural consequence of aging, they are not necessarily inevitable. You may be able to delay their onset by not smoking, limiting exposure to sun, taking vitamin E supplements and eating produce rich in vitamin C and carotenoids, two in particular.
Two New Carotenoid Heroes. Research shows that dark green leafy vegetables--especially kale, collards and spinach--and other foods rich in the carotenoids lutein and zeaxanthin (see chart) may protect against ARMD.
Lutein and zeaxanthin are pigments found in concentrated amounts in the retina. They protect eyes in two ways. "First," says Hammond, "they filter out the most damaging portion of the UV spectrum--blue light." Second, they act as antioxidants, protecting against the oxidation of lipids in the eye.
"We're seeing low levels of these two nutrients in the retinas of people with both age-related macular degeneration and cataracts," adds Hammond. In addition, he notes, the people he sees with eye disease have low intakes of dietary lutein and zeaxanthin. Previous studies support his observations.
The ground-breaking Eye Disease Case-Control Study, for example, showed that taking in more carotenoids in general decreased the risk of ARMD by 43%. The strongest link was to lutein and zeaxanthin. They were the standouts in a group of over 50 naturally occurring pigments, which include beta-carotene and lycopene, found mostly in dark green, orange and yellow vegetables and brightly colored fruits.
Can Other Antioxidants Improve the View? Vitamin E, a known quencher of the damaging free radicals that oxidation unleashes, is another nutrient that shows some promise in preventing cataracts. Earlier this year, the Beaver Dam Study, an ongoing study of a community in Wisconsin, provided evidence. In more than 250 people, high blood levels of vitamin E were linked to a lower incidence of cataracts. Last year, a larger, four-year study, funded by the National Eye Institute, found that people taking vitamin E supplements cut their risk of cataracts in half. Other studies, however, have not found as much benefit.
Researchers speculate that another well-known antioxidant nutrient, vitamin C, might also aid eyesight. The lens of the eye normally contains high concentrations of vitamin C, but as you age the amount decreases. Moreover, blood levels of vitamin C are low in people with cataracts. It seems plausible, then, that getting more C would help replenish eye stores of the vitamin, presumably preventing cataracts from forming, though that link is not yet proven.
Some speculate that vitamin C's role may be an indirect one. It's known to help vitamin E be a more effective antioxidant and may similarly aid carotenoids, freeing them to do their eye-saving magic. So getting your daily dose of C from rich sources like kiwis, strawberries and orange juice is still wise for the eyes.
The Bottom Line. Although the experts don't know for sure yet which nutrients best prevent age-related eye diseases, the odds are good that eating more fruits and vegetables will help.
Can you play catch up? Cataracts and age-related macular degeneration occur over time and the consequences are cumulative, so start now, whatever your age. Researchers believe antioxidant nutrients, including carotenoids, may not only help prevent eye diseases, but may help prevent further deterioration of existing conditions.
Vitamin C and the carotenoids lutein and zeaxanthin are easily gotten in a diet rich in nutrient-packed produce. Lucky for you, with increasing evidence of the preventive power of fruits and vegetables for many other diseases, such a menu probably helps preserve more than your eyesight.
Finding Lutein and Zeaxanthin
Fruit or Vegetable Lutein and Zeaxanthin
Kale, 1/2 cup cooked 10.3
Spinach, 1 cup raw chopped 6.7
Spinach, 1/2 cup cooked 6.3
Turnip greens, 1/2 cup cooked 6.1
Collard greens, 1/2 cup cooked 5.2
Corn (yellow), 1 fresh ear cooked 2.3
Broccoli, 1/2 cup cooked 1.7
Romaine lettuce, 1 cup fresh shredded 1.5
Zucchini, 1/2 cup raw 1.4
Broccoli, 1/2 cup raw chopped 1.1
Green peas, 1/2 cup canned 1.1
Brussels sprouts, 1/2 cup cooked 1.0
Corn (yellow), 1/2 cup canned 0.7
Orange, 1 medium 0.2
Papaya, 1 fresh whole 0.2
Tangerine, 1 medium 0.2
Source: USDA-NCC Carotenoid Database (1998).
By Catherine Golub, M.S., R.D.
CAN SUPPLEMENTS SAVE YOUR SIGHT?
There are plenty of supplements marketed for eye health. Are they a good idea?
Ocuvite (see EN, September 1998) contains vitamins C and E, as well as high-dose zinc (which is under study, but is still controversial). It also contains beta-carotene, but no lutein or zeaxanthin, the carotenoids with the most evidence of help.
Xangold contains lutein, betting that it's the most important carotenoid for eyes. Some researchers think lutein is more beneficial than zeaxanthin, but since the two carotenoids tend to occur together in foods, this is difficult to discern.
Bright Eyes gum contains anthocyanins. These are potent antioxidants that may indeed be valuable for eyes and general health, but not necessarily more than other antioxidants. You can get them in fruits and vegetables, especially blueberries, cranberries, tea and grape seeds.
Perhaps most important, since carotenoids may compete with each other for absorption and since other carotenoids are beneficial for other reasons, EN recommends getting them in their natural mix, as found in foods.