Dark, leafy greens help shield eyes from cataracts

New research provides further evidence that substances in kale, spinach and other green vegetables help protect aging eyes from cataract.

In an experiment, investigators found that human eye cells treated with antioxidants called lutein and zeaxanthin showed less damage after being exposed to ultraviolet rays, the sunlight ingredient considered a major contributor to cataracts.

Cataracts occur when proteins in the eye's lens begin to clump together, forming a milky cloud that obscures vision. Currently, around 20 million Americans have cataracts, and research suggests that the more sunlight you are exposed to in life, the greater your risk.

It's hard to say how much of each antioxidant people should get in their diets, given that little is known about how antioxidants in the bloodstream reach the eyes, says study author Dr. Joshua A. Bomser.
"While the specific experiments haven't been done...we know generally: eat more fruits and vegetables," he said.

Foods that contain particularly high doses of lutein and zeaxanthin include kale, collard greens, broccoli, turnip greens and spinach.
Bomser explained that there is ample evidence to suggest that people who eat a lot of fruits and vegetables seem to have a lower risk of age-related cataracts.

To investigate why, Bomser and his colleagues at Ohio State University in Columbus grew human lens cells in a laboratory, then added lutein, zeaxanthin, vitamin E, or left the cells alone.

The researchers then exposed the eye cells to ultraviolet (UV) radiation, in order to mimic the effect of sunlight.

In an interview, Bomser explained that lens cells mixed with lutein and zeaxanthin showed significantly less damage following UV-exposure than cells that had no shielding from antioxidants.

And although vitamin E appeared to offer some protection from UV rays, it was surpassed by both lutein and zeaxanthin, he and his colleagues note in the Journal of Nutrition.

However, other research shows that both vitamins E and C appear to protect body cells from damage from free radicals, which are a normal byproduct of metabolism, Bomser noted.

He added that it's always better to eat antioxidant-rich foods than supplements, in order to get the benefits of other healthy substances present in foods. However, barring that, research does suggest that people can also benefit from taking lutein and zeaxanthin supplements, Bomser said.