One expert explains why kale is important to vision and how people really are what they eat.
Mom always said to eat those carrots—they’ll improve your eyesight. Some people attribute that old belief to World War II propaganda that claimed munching on carrots was the reason British pilots had perfect night vision (they were actually using radar). Is there a kernel of truth in Mom’s pleas? Not really, says one expert, Emily Y. Chew, a spokeswoman for the American Academy of Ophthalmology and deputy director of epidemiology and clinical applications with the National Eye Institute at the National Institutes of Health. Dr. Chew explains why kale is important to vision and how people really are what they eat.
Not Better, but Not Worse
Nearly every doctor will tell patients to eat a healthy diet rich in vegetables and fish, but while the NIH has done several long-term studies on the eye and diet, none has been able to show eye damage can be reversed, says Dr. Chew. “You really cannot make your eyesight better, but you can prevent it from getting worse,” she says.
And what about carrots? “They may be important to the body, but there is no evidence that they do anything specifically to the eyes,” she says.
The first NIH study on eyes and diet was the Age-Related Eye Disease Study (AREDS), which looked at nearly 5,000 patients for more than a decade. In 2001, the study concluded that a supplement containing vitamins C and E, beta-carotene and zinc reduced the risk of developing advanced age-related macular degeneration (AMD)—a disorder that erodes central vision and is the top cause of blindness in the U.S.—by 25% in five years.
“We also studied people’s dietary habits and found that those eating the highest amounts of leafy greens, like kale, collard greens and spinach, had a 40% reduction in the likelihood of having AMD” compared with those eating very little greens, says Dr. Chew, one of the study’s researchers. The same was true for people who ate fish high in omega-3 fatty acids at least twice a week.
Among the foods found to cut the risk of age-related macular degeneration: Fish high in omega-3 fatty acids.
The study discovered that lutein and zeaxanthin, members of the carotenoid family present in large amounts in leafy greens, were the main component of the macula, a small spot near the center of the retina that’s responsible for clear vision. However, at the time, those carotenoids weren’t yet commercially available as supplements. Omega-3 fatty acids were found to be present in abundance in the retina. Beta-carotene, which carrots contain, wasn’t found.
In 2006, the NIH started a follow-up study to test whether adding these three ingredients to the AREDS supplement would further stave off eye disease. The results: “We found about a 20% decrease in the risk of progressing to advanced AMD for those who took the AREDS formula containing lutein and zeaxanthin versus the old AREDS supplement without it.”
The follow-up study also looked at people who ate almost no leafy greens in their diet. They were randomly assigned the new AREDS supplement with lutein and zeaxanthin and the old formulation. That part of the study found a 26% reduction in the risk of advancing AMD in those on the new supplement, proving lutein and zeaxanthin are preventive. The study also concluded that beta-carotene supplements increased the incidence of lung cancer in current and former smokers. “Though people could never consume that much beta-carotene by just eating carrots,” Dr. Chew adds.
The Gene Factor
The Rotterdam Eye Study, a continuing study that began in 1990, looked at genetics and diet, with surprising findings. “The study showed that, if you have the bad AMD genes, you can actually eat away the genetic factor by switching to a diet high in vitamins A, C and E and other antioxidants like zinc, lutein and zeaxanthin,” Dr. Chew says.
No one has been able to prove that omega-3 supplements made a significant difference to eyesight, though consuming fish does. “So maybe it’s true that you can’t fool Mother Nature, and eating foods with vitamins is more important than taking supplements,” she says.
Not Too Late to Start
The damage may already be done, but people can stop further vision deterioration by eating a healthier diet, Dr. Chew says. “It does appear that certain foods work in concert together, and that food as food—and not just as supplements—is important,” she says.
Dr. Chew suggests eating fish two times a week and leafy greens several times a week.
By HEIDI MITCHELL, The Wall Street Journal
April 6, 2015