Can a Healthy Diet Help Protect Vision?
No one knows how to prevent the eye disorders that often come with aging, though not smoking and avoiding strong sunlight may help reduce the risk of cataracts. That's why there has been so much interest in the role of nutrition in eye health, which has generated hundreds of studies in recent yearsand many promising leads.
It's clear that malnutrition harms vision. A shortage of vitamin A, for example, causes night blindness and other problems. Thus, carrots really are good for your eyes, since they're rich in beta carotene, which the body converts into vitamin A. Vitamin deficiencies can also cause eye disorders such as cataracts in lab animals.
Other nutrients and plant compounds may help protect vision, perhaps by acting as antioxidants and reducing inflammation. These include two other carotenoids, lutein and zeaxanthin, which are antioxidant pigments in many vegetables and fruits. Lutein and zeaxanthin are also found in the retina of the healthy eye, specifically in the macula (the part of the retina responsible for detailed central vision), where they act as a filter against ultraviolet radiation and other harmful components of sunlightsort of like built-in sunglasses.
Nearly half of us will eventually develop cataracts, a clouding of the lens that is easily corrected with outpatient surgery. Less common but also less treatable is age-related macular degeneration (AMD), the leading cause of blindness among older people. Certain nutrients appear to play a role in preventing AMDor at least delaying itand possibly cataracts.
Eye and Nutrition Research
Here are the nutrients and supplements most often promoted as ways to preserve vision in healthy people and prevent AMD and/or cataracts, along with what the research shows:
- Lutein and zeaxanthin. Most (but not all) observational studies have found that people with high dietary intakes or high blood levels of these carotenoids have a reduced risk of AMD and cataracts. Some small short-term clinical trials have also suggested protective effects in people with healthy eyes, as well as benefits in those who already have AMD. More research is needed.
- Vitamin C and E, selenium, beta carotene and other antioxidants. Again, some studies have found that people who consume plant foods rich in such antioxidants are at reduced risk for cataracts and AMD. For instance, a recent British study found that older vegetarians are 30 to 40 percent less likely to develop cataracts, compared to daily meat eaters. But there's little evidence that antioxidant supplements have this effect. Last year a large eight-year Harvard study of male doctors found that vitamin C and E supplements, alone or in combination, did not reduce the risk of cataracts. And a review by the Cochrane Collaboration in 2009 concluded that vitamin E and beta carotene pills do not reduce the risk of AMD. Moreover, high doses of beta carotene increase the risk of cancer in smokers.
- Zinc. This mineral, essential to good vision, is found in the retina, and it may protect eye tissue from the damaging effects of light and from inflammation. But supplemental zinc has never been found to be beneficial to healthy eyes. In addition, high doses (more than 50 milligrams daily, as in many eye supplements) can have adverse effects. Unless you have AMD, get zinc from food.
- Omega-3 fats. Several large observational studies have linked fish intake (in particular, fish rich in omega-3 fats) to reduced AMD incidence and progression, and possibly to reduced risk of cataracts. The most recent study, in the Archives of Ophthalmology in June, found that women who consumed the most omega-3s from fish were 40 percent less likely to develop AMD than those with the lowest intake.
- Herbal supplements, such as bilberry and ginkgo. Many herbs show up in various eye supplements, often combined with high doses of vitamins. Bilberries contain carotenoids and other pigments (anthocyanins) that may be good for vision. Despite the many claims and some promising lab research, so far there's no convincing evidence that any herb or eye supplement can keep your eyes healthy.
Focus on Diet and Eye Health
Some research, including data from the well-known Women's Health Initiative, suggests that a healthy diet (as opposed to individual nutrients) can protect against eye disorders. In fact, it seems that the dietary habits that contribute to cardiovascular healthand that may protect the brain and help prevent some cancersare also good for your eyes. Here are the basics:
- Emphasize colorful fruits and vegetables. In particular, leafy greens such as kale and spinach are rich in carotenoids and may protect against AMD and cataracts. Blueberries, blackberries, beets, broccoli and carrots are also excellent choices. Colorful foodsdeep green, orange, yellow, purple, red, bluecontain the most carotenoids and other healthy pigments.
- Opt for healthy fats, as in fish and nuts, which may benefit the retina.
- Get more zinc, which is plentiful in foods. Meat, seafood (especially oysters) and liver are the richest sources. Brewer's yeast, milk and other dairy products, beans, wheat germ and whole grains also supply some zinc.
Other tips: Smoking endangers your eyesso if you smoke, this is another reason to quit. Stay out of smoky rooms. Get regular eye examsonce every three to five years starting at age 39, more often as you get older, depending on your health and on professional advice.
Nutrition and Eye Health for People with AMD
The important Age-Related Eye Disease Study (AREDS), conducted by the National Eye Institute, found that one formula (500 milligrams of vitamin C, 400 IU of vitamin E, 15 milligrams of beta carotene, 80 milligrams of zinc and 2 milligrams of copper) can slow the progression of age-related macular degeneration (AMD) in many people who have been diagnosed with it. Copper was included in the AREDS formula because high doses of zinc can lead to copper-deficiency anemia. The formula was originally marketed by Bausch & Lomb (as PreserVision), but is now made by other companies as well. Several studies have confirmed that this formula can help save vision in people with AMD.
An ongoing second AREDS study is testing omega-3 fats, lutein and zeaxanthin in people with AMD, along with formulas with less zinc and no beta carotene.
There's no evidence that the AREDS formula helps prevent AMDit is usually recommended only for people who already have the disorder. Still, if you're at high risk for AMD (because a parent had AMD, for instance), you should discuss the AREDS formula with an eye-care specialist. The AREDS study found that the formula had no effect on the development or progression of cataracts.
Source: Originally published in The University of California, Berkeley Wellness Letter (November 2011)