Higher lutein and zeaxanthin levels may help protect against cataract

Tuesday, March 13, 2012. In an article published in advance of print in the British Journal of Nutrition, 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. Lutein and zeaxanthin's protective effect against another eye disease--age-related macular degeneration—is well known, however their effects in other eye conditions have been less well explored.

"Reactive oxygen species can damage lens proteins and fiber cell membranes, leading to cataract formation," the authors write. "Lutein and zeaxanthin are the most abundant carotenoids that accumulate in the lens of the eye, where they possibly filter phototoxic blue light and neutralize reactive oxygen species."

The current study included 1,130 men and 559 women who enrolled in the Kuopio Ischemic Heart Disease Risk Factor Study from 1998-2001. Blood plasma samples collected between 2005 and 2008 were analyzed for alpha tocopherol, vitamin A and carotenoids.

From the beginning of the current investigation through 2008, 113 cataracts were diagnosed, including 108 nuclear cataracts (the most common cataract type, believed to be caused in part by free radical damage), resulting in a four year nuclear cataract incidence of 6.4 percent. 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 cross-sectional studies have found a lower risk of nuclear cataract or their progression in association with higher serum levels or dietary intake 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."

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