Eat Your Greens
How Kale Could Save Your Eyesight
Thousands of aging Americans lose their eyesight each year. Many more suffer from significantly impaired vision. Now, new studies suggest that simple dietary factors may be able to slow the onset of, or completely prevent, common, age-related eye diseases.
Dr. Julie Mares, an associate professor in the Department of Ophthalmology at the University of Wisconsin-Madison, is studying the connection between diet and eyesight. Her research suggests that pigments found in certain fruits and vegetables may combat the leading causes of cataracts and macular degeneration, two of the most common eye diseases afflicting older populations.
Frequent and intense exposure to ultraviolet light, as found in sunlight, can damage the proteins in the lens of the eye. Over time, these damaged proteins accumulate in the lens and clump together. These accumulations, called cataracts, cause vision to become blurry and spotted.
Ultraviolet light also damages the macula, the part of the eye that provides central vision and distinguishes fine detail. The greater the exposure to sunlight, the greater the risk of harm to this area of the eye. As damage to the macula becomes substantial, the center of one's field of vision becomes increasingly blurry and the ability to see fine details is lost.
According to Mares, seven percent of all adults over the age of 70 develop macular degeneration. And, she points out, "Once you have it, you are basically going blind."
While a lifetime of exposure to sunlight puts older adults at a greater risk of developing these diseases, Mares is hopeful that dietary factors could minimize the risk.
Carotenoids, a type of pigment found in plant and animal tissues, are able to absorb the same light waves that cause damage to the eye. When these pigments are abundant in the eye, they absorb much of the incoming ultraviolet light. By effectually blocking these light waves from reaching the proteins or the macula, these pigments protect the eye from harmful exposure and subsequent damage.
In particular, the carotenoids lutein and zeaxanthin have been shown to absorb ultraviolet light that enters the eye. Researchers are particularly interested in these two pigments because they are the only carotenoids that occur in large quantities in the human eye.
Lutein and zeaxanthin are found in many fruits and vegetables but occur in their highest concentrations in dark leafy greens such as kale, spinach and collards. Researchers are now trying to pin down whether or not a diet rich in these pigments can increase the amount of the pigments accumulated in the eye.
According to Mares, early results are promising. Studies have consistently demonstrated a lower incidence of cataracts in populations with higher carotenoid intake. For instance, in a recent study of adults with cataracts in Beaver Dam, Wis., people who increased their intake of lutein and zeaxanthin by changing their diets to include more leafy green vegetables had a 50 percent lower risk of developing new cataracts.
There is also compelling evidence that these pigments are beneficial for people with macular degeneration. In a national study of people in intermediate stages of the disease, progression to late stage macular degeneration was slowed by 30 percent in those who were given high-dosage supplements of the pigments.
"But it's still early," Mares cautions. While research has shown a strong correlation between the concentration of these pigments in the eye and the occurrence of age-related eye disease, the role of dietary sources of these pigments is still being explored.
It has not yet been conclusively demonstrated that the consumption of foods or supplements rich in these pigments can alter the concentration of the pigments in the eye. Other factors, such as genetic predisposition and general lifestyle, are difficult to separate from diet, making it hard for scientists to isolate the specific role that diet plays.
However, Mares notes that doctors are advising individuals with a family history of age-related cataracts, as well as people in early stages of macular degeneration, to take supplements containing high dosages of these pigments.
Her best advice, though, is to eat a healthy diet that is rich in most vitamins and minerals.
"We still don't know if it's the lutein or something else in the diet that is lowering the risk," she says. "So, the best bet is to eat a well-balanced diet."
Continuing research efforts hope to develop a better understanding of the link between diet and eyesight. While current findings are still largely inconclusive, Mares believes they are promising. And, if current findings are validated by future research, thousands of adults may be able to enjoy better eyesight longer thanks to simple changes in their diet.