You already know that leafy greens like spinach and kale are incredibly good for you—loaded with vitamins, minerals, antioxidants and fiber. But here’s a new one: Leafy greens contain high levels of the important carotenoids lutein and zeaxanthin, which are known to protect the eyes against macular degeneration, and, according to the results of a recent study*, also seem to protect older people’s eyes from cataracts.

Jouni Karppi and Sudhir Kurl at the University of Eastern Finland in Kuopio and Jari Laukkanen of Lapland Central Hospital in Rovaniemi, Finland report that increased plasma levels of the carotenoids lutein and zeaxanthin are associated with a lower risk of cataract in older men and women.

For the study, blood plasma samples from 1,130 men and 559 women were collected between 2005 and 2008 and were analyzed for alpha tocopherol, vitamin A and carotenoids. Among subjects whose lutein levels were among the top one-third of participants, there was a 42 percent lower risk of being diagnosed with nuclear cataract, and for those whose zeaxanthin levels were among the top third, the risk was 41 percent lower compared to subjects whose plasma levels were in the lowest third.

While three previous studies have found an association between reduced risk of nuclear cataract and higher consumption of lutein and zeaxanthin, the current study's authors note that a recent FDA review concluded that there was no credible evidence to support a protective effect for lutein or zeaxanthin on cataract risk. However, Dr Karppi and colleagues remark that there are factors that could explain previous inconsistent study results.

"We observed that high concentrations of lutein and zeaxanthin were associated with a reduced risk of nuclear cataract in elderly subjects," they conclude. "There may be other protective factors of the diet (e.g. synergism of carotenoids with vitamin C or other antioxidants) that may partly explain the observed results."

Did you know these added benefits of leafy greens in your diet?