The same advice for a healthy heart - eat fatty fish twice a week - might also keep your vision clear as you age.
According to a study soon to be published in the American Journal of Clinical Nutrition, increasing your intake of fish can help lower the odds of developing the advanced form of age related macular degeneration (AMD).
AMD affects close to one million Canadians over the age of 50, a number that expected to increase by 50 per cent over the next two decades.
It's a chronic 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 a car, read a book and recognize faces.
There are two types of AMD: wet and dry. Dry is more common and occurs when the macula thin gradually with age. Wet AMD is caused when abnormal blood vessels grow under the macula.
The exact cause of AMD is unclear, but factors such as genetics, family history, cigarette smoking, high blood pressure, excessive sunlight exposure and a diet low in antioxidants are linked with a greater risk. (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.)
Previous studies have linked higher intakes of fish with a lower risk of developing AMD. Research has also hinted that eating more fish may reduce the likelihood of the disease progressing to an advanced stage.
In the current study researchers investigated omega-3 fatty acid intake among 1,837 older adults with AMD who had participated in AREDS (Age-Related Eye Disease Study). (AREDS was a randomized controlled trial that found a daily regimen of antioxidant vitamins and minerals delayed the onset of advanced AMD by 25 per cent.)
Those with the highest intake of omega-3 fats from fish and seafood - the equivalent of eating about 3 ounces of Atlantic salmon or 5 ounces of rainbow trout per week - were 30 per cent less likely to progress to advanced AMD over 12 years than their peers who consumed the least (virtually none).
Inflammation is thought to play a role in the development of AMD. One omega-3 fatty acid in fish, called DHA (docosahexaenoic acid), is concentrated in the retina where it's thought to prevent degenerative changes through its anti-inflammatory and antioxidant properties.
AREDS2, a five year randomized trial involving 4,000 people, is now under way to test the effectiveness of supplementing with certain antioxidants and/or omega-3 fatty acids on the progression to advanced AMD.
This isn't the first study to suggest certain foods can help preserve your vision. Previous research has revealed that a regular intake of nuts, fruits and vegetables can help prevent AMD, while consuming too much fat, alcohol and refined foods can increase the risk.
The following foods and nutrients may help keep your vision sharp as you age.
To increase your intake of DHA and EPA, the two omega-3 fatty acids in fish, include fish in your diet twice per week. The best sources include salmon, trout, sardines, herring and Arctic char.
If you don't like fish, consider taking a fish-oil capsule once or twice daily. If you're a vegetarian, DHA supplements made from algae are available.
Eating nuts has been linked to a lower risk of macular degeneration. Nuts, which have anti-inflammatory and antioxidant effects, may reduce the risk of cardiovascular disease and type 2 diabetes, diseases linked to AMD. Include 1 serving (1/4 cup) of nuts in your diet a few times each week.
This phytochemical, abundant in leafy greens, is concentrated in the macula where it protects from damaging UV light. A high intake of lutein from foods has been linked with a lower risk of AMD.
The best sources of lutein are spinach, Swiss chard, kale, collard greens and rapini but you'll also find some in green peas, broccoli, Brussels sprouts, nectarines and oranges.
Studies have found that higher blood levels and higher dietary intakes of zinc are linked with a lower risk of AMD. However findings from studies using zinc supplements have been mixed.
The mineral may protect from macular degeneration by nourishing cells in the retina. Zinc-rich foods include oysters, seafood, red meat, poultry, yogurt, wheat bran, wheat germ, whole grains and enriched breakfast cereals.
Research suggests that people who consume the most antioxidants - vitamins C, E and beta-carotene - from regular foods are significantly less likely to develop AMD.
Vitamin C rich foods include citrus fruit, cantaloupe, kiwi, mango, strawberries, broccoli, Brussels sprouts, cauliflower, red pepper and tomato juice. To increase vitamin E, include wheat germ, nuts, seeds, vegetable oils, whole grains and kale in your diet. Beta-carotene is plentiful in dark green vegetables as well as carrots, winter squash, sweet potato, nectarines, peaches, mango and papaya.
If you're at risk for developing advanced AMD, discuss antioxidant supplementation with your eye care doctor. The special formula used in AREDS 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 name Vitalux (Novataris) in drug stores. (Smokers with AMD should choose a beta-carotene free formula.)
The AREDS formula is not intended for healthy people who don't have AMD. This 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.
Low glycemic foods
Evidence hints that a diet based on refined (white) carbohydrates and sugary foods, or high glycemic foods, boosts the risk of early AMD. It's thought that these foods may contribute to inflammation and oxidative damage in the retina.
Include low glycemic foods at meals such as beans, lentils, nuts, pasta, brown rice, sweet potatoes, steel-cut or large-flake oatmeal, oat bran and bran cereals. Other low glycemic foods include fruits include apples, oranges, peaches, pears, berries, yogurt, milk and soy beverages.
Leslie Beck, a Toronto-based dietitian at the Medcan Clinic, is on CTV's Canada AM every Wednesday. www.lesliebeck.com .