Cataract prevention and nutrition
Age-related cataracts are a leading cause of blindness in the world today. Currently, the only treatment for cataracts is surgical removal of the cloudy lens, which typically is then replaced with an intraocular lens (IOL) during cataract surgery.
While the exact cause of cataracts is unknown, experts believe that oxidative stress damages certain enzymes and proteins in the eye's natural lens, which causes the lens to become cloudy.
And though some research has produced conflicting results, eating a healthy diet rich in antioxidants and certain vitamins has been shown in several studies to be associated with a reduced risk of cataracts or their progression.
Diet, oxidative stress and cataracts
Oxidative stress results when there is an imbalance between damaging free radicals roaming the body and the antioxidants that keep them in check.
Free radicals are atoms or groups of atoms (molecules) that are highly reactive with other atoms and molecules because they have unpaired electrons.
In the body, a free radical usually is an oxygen molecule that self-stabilizes by taking an electron from another molecule, which in turn tries to take an electron from another molecule, and so on.
Free radicals damage the body by stealing electrons from the normally healthy cells of organs and other tissues. This process of stealing electrons from healthy cells is called oxidation.
In the eye, oxidation affects proteins and fats in the lens to the extent that the lens becomes damaged and cloudy, creating a cataract. Preventing free radical damage with healthy foods, particularly those containing antioxidants, may help slow down this process.
Free radicals that damage our eyes and the rest of the body may originate from eating unhealthy foods, exposure to pollution or chemicals, smoking and ultraviolet radiation.
Some free radicals occur from normal daily metabolism, which means even people who don't have these risk factors need antioxidants found in healthy foods.
Healthy foods and cataract prevention
People who consistently follow a healthy diet that includes colorful fruits, vegetables and whole grains may show a decreased risk of cataracts. Antioxidant vitamins and phytochemicals found in fruits and vegetables that may reduce the risk of cataracts include vitamins A, C and E, lutein and zeaxanthin.
In a study of more than 30,000 women age 49 and older, researchers in Sweden found that women whose diet contained the highest total antioxidant capacity (TAC) were significantly less likely to develop cataracts compared with those whose diets were low in antioxidants. The main contributors to dietary TAC in the study population were fruits and vegetables (44.3 percent), whole grains (17.0 percent) and coffee (15.1 percent).
In an Australian study of more than 1,600 adults, researchers found that individuals in the top 25 percent for total carbohydrate intake had more than three times the risk for cataracts than those in the lowest 25 percent for carbohydrate intake.
A large study of adult women in Iowa, Wisconsin and Oregon found that eating foods rich in a variety of vitamins and minerals may help delay the development of cataracts.
In an earlier study published by the same researchers, the study authors found women whose diets were rich in lutein and zeaxanthin had a decreased prevalence of cataracts than women with lower intakes of these carotenoids.
A 10-year study of more than 2,400 older adults in Australia found that higher intakes of vitamin C or the combined intake of multiple antioxidants reduced the risk of cataracts in this population.
A Japanese study linked cataract formation to oxidative stress associated with decreased levels of antioxidants in the lenses of affected eyes.
However, other studies have failed to show an association between nutritional supplements and reduced risk of cataracts.
In two long-term Age-Related Eye Disease studies (AREDS and AREDS2) sponsored by the U.S. National Eye Institute, neither study found use of daily multivitamin supplements containing vitamin C, vitamin E and zinc (with or without beta-carotene, lutein and zeaxanthin, and omega-3 fatty acids) prevented or slowed the progression of cataracts.
And while all nutrients, antioxidants and phytochemicals associated with cataract prevention in studies can be found in eye vitamins and vision supplements, many experts believe these substances should be acquired from a healthy diet rather than from nutritional supplements.
But if your diet lacks key nutrients because you don’t eat enough fruits and vegetables, it may be wise to consider taking one or more daily nutritional supplements to make sure you are getting all the nutrients you need for optimum eye health.
Prior to embarking on a regimen of eye vitamins and other nutritional supplements, consult an eye doctor. In some cases, taking too much of a specific vitamin or nutrient could be harmful to your health.
Shape up your diet for good vision
So exactly what is a healthy diet?
A healthy diet that provides good nutrition for healthy eyes includes five to nine servings of fruits and vegetables every day, at least three servings of 100 percent whole grains each day and two servings of fish each week.
The total calories consumed should be just enough to keep you at a healthy weight, based on your individual activity level and metabolism.
Dark green and colorful fruits and vegetables are great sources of eye-friendly antioxidants. They also contain folic acid and calcium — important nutrients which also may help reduce the risk of cataracts and should be included in a healthy diet.
To maintain a healthy diet, it is equally important to avoid fried foods, processed foods and sugary snacks and soft drinks — all of which appear to be associated with an increased risk of cataracts, as well as obesity and other health problems.