Most of us know that what we eat can affect waistline, arteries, and even our brain. But how many people think of their eyes when scanning a nutrition label or reading a menu?
It seems the right foods -- and supplements -- can help preserve vision as you age.
According to a new study published in last month's Journal of the American Medical Association, eating foods loaded with beta carotene, along with those rich in vitamin C, vitamin E and zinc, can dramatically reduce the risk of age-related macular degeneration in older people.
Age-related macular degeneration (AMD) is a disease that attacks the central part of the retina, called the macula, which controls fine, detailed vision. The condition results in progressive loss of visual sharpness, making it difficult to drive, read and recognize faces. AMD, in varying stages of severity, affects more than two million Canadians over the age of 50 and is the leading cause of severe vision loss in older adults.
The exact cause of AMD is unclear, but factors such as family history, smoking, high blood pressure, excessive exposure to sunlight, obesity and a diet low in antioxidants are linked with a greater risk of developing the disease. Antioxidants are thought to protect cells in the retina from the harmful effects of free radicals, unstable molecules formed from cigarette smoke, pollution and ultraviolet light.
A landmark study, the Age-Related Eye Disease Study, published in 2001, found that among 3,640 older adults with varying stages of AMD, those taking a high dose combination of antioxidants (beta-carotene, vitamin C, vitamin E) and zinc reduced the risk of the disease progressing to its advanced form by 25 per cent.
In the current study, Dutch researchers sought to determine if beta carotene, vitamin C and E and zinc, as present in normal daily foods, could prevent AMD in healthy older adults. The researchers followed 4,170 adults, 55 or older, for an average of eight years and found those who consumed greater amounts of vitamin E and zinc were about 10 per cent less likely to develop AMD. Consuming higher amounts of all four nutrients offered the greatest protection; individuals with above average intakes had a 35 per cent reduced risk of AMD.
This isn't the first study to suggest certain foods can keep your eyes younger as you age. Previous research has revealed that a regular intake of fish, nuts, fruits and vegetables can help prevent AMD, whereas consuming too much fat, alcohol and too many baked goods can increase one's risk. Dietary factors may also play a role in the development of cataracts, a condition where the lens of the eye clouds over, making it difficult or nearly impossible to see.
Degenerative eye changes are a normal part of aging, but vision loss isn't inevitable.
The following foods and nutrients may help keep your vision sharp. The key: Start making dietary changes early.
Antioxidants
Based on this new study, it seems wise to increase your intake of antioxidant-rich foods. To boost your intake of vitamin E, add nuts, seeds, wheat germ, avocado, whole grains and kale to your diet. Good sources of vitamin C include citrus fruit, kiwi, green peppers, broccoli and tomato juice. Beta carotene is plentiful in bright orange and dark green produce such as carrots, sweet potato, winter squash, peaches, cantaloupe, kale and spinach.
If you already have AMD, discuss antioxidant supplementation with your eye-care doctor. The special formula used in the Age Related Eye Disease Study contained vitamin C (500 milligrams), vitamin E (400 international units), beta carotene (15 milligrams), zinc (80 milligrams) and copper (2 milligrams). The formula is sold under the brand names Vitalux (Novataris) and Ocuvite (Baush & Lomb) in drug stores.
The study formula is not intended for healthy people who don't have AMD. This high dose supplement was shown only to benefit people with intermediate or advanced AMD. Researchers don't yet know if the formula is effective in people with early stages of the disease.
Aside from AMD, antioxidants may also protect the eye's lens in animal studies but the evidence isn't rock solid in humans. There's consistent evidence that multivitamin users are less likely to get cataracts.
And some studies -- but not all -- suggest that taking vitamin C supplements for at least five years can prevent the development of early cataracts in women.
Lutein
This compound is found mostly in fruits and vegetables, especially leafy greens. Once consumed, lutein makes its way to the eyes, where it's thought to protect the retina and lens from oxidative damage. Studies have found that people who get the most lutein from their diet have a 20 lower risk of cataract, compared to people who consume the least. Some studies suggest that lutein-rich foods lower the odds of AMD, but others do not.
Scientists speculate that an intake of six to 15 milligrams of lutein per day is optimal for eye health.
The best sources include kale, Swiss chard, collard greens, green peas, broccoli, romaine lettuce, brussel sprouts, nectarines and oranges. Don't count on a multivitamin with added lutein to get up your daily dose -- most provide no more than 0.5 milligrams per tablet.
Zinc
This mineral may guard against AMD by nourishing cells in the retina. Zinc is also used by many enzymes important in the eye. The best food sources include lean meat, poultry, fish, seafood, whole grains, wheat bran, wheat germ and dairy products.
Fish
If you have AMD, consider adding oily fish to your diet. A study from Australia found that among 3,654 people with AMD, those who ate fish more than once a week were half as likely to have late-stage AMD, compared to those who ate fish less than once per month. The human eye contains a high proportion of omega-3 fats, especially DHA, which is abundant in fish and seafood. DHA is necessary for the normal functioning of the retina. The best sources of DHA include salmon, trout, sardines, anchovies and herring.
Leslie Beck, a Toronto-based dietitian at the Medcan Clinic, is on CTV's Canada AM every Wednesday. Visit her website at lesliebeck.com.
Leslie Beck