March 28, 2000 (Indianapolis) -- There have been many studies of the relationship between intake of antioxidant vitamins, thought to reduce damage in the body from everyday living and unhealthy habits, and the risk for cataracts. Some have produced conflicting findings. A new study in the March edition of the journal Ophthalmology suggests that certain vitamins may reduce the risk for some types of cataracts. Intake of polyunsaturated fat, protein, or spinach may also be helpful.
A cataract is a cloudy or opaque area on the normally clear lens of the eye. The three kinds of cataracts are usually described by their location on the lens. The most common type, usually associated with aging, is the nuclear cataract that occurs in the center of the lens. The cortical cataract, most often seen in people with diabetes, begins as wedge-shaped spokes at the outer edges of the lens and progresses as the spokes move toward the center. The subcapsular kind develops slowly from a small opaque area, usually at the back of the lens.
"The Blue Mountains Eye Study was set up in 1992 to study the causes of the common eye diseases that affect older people: cataract, macular degeneration, and glaucoma," says lead author Robert G. Cumming, PhD, in an interview with WebMD. "We studied the three main types of cataract: cortical cataract (which affected 24% of people in our study), nuclear cataract (19%), and posterior subcapsular cataract (6%). Some people had more than one type." Cumming is associate professor in the department of public health and community medicine at the University of Sydney in Australia.
The researchers enrolled almost 3,000 people in the study, which will look at the development of cataracts over time. This initial report deals with the cataracts that are already present at the beginning of the study, and looks at the impact that past dietary habits may have had. Investigators also are looking at other factors that may have an influence on cataract development.
They found that higher intakes of protein, vitamin A, niacin, thiamin, and riboflavin were associated with lower levels of nuclear cataract. Intake of polyunsaturated fats, found in vegetable oils, fish, and fish oils, was associated with reduced levels of cortical cataract. No nutrients were associated with posterior subcapsular cataracts.
"These findings support other research suggesting that antioxidant vitamins reduce the risk of cataract", says Cumming. "Several B group vitamins -- riboflavin, niacin and thiamine -- were also associated with reduced risk of nuclear cataract." The only food associated with cataract prevention was spinach - perhaps due to its high content of a nutrient called lutein.
Cristina Leske, MD, MPH, is distinguished professor of preventive medicine and ophthalmology at the SUNY Stony Brook Campus. She tells WebMD that the study is well done and confirms what others have found in earlier research. Leske was not involved in the study.
"The problem with an observational study like this one, is that it looks at associations between diet and cataracts, but not in a way that allows us to say cataracts are caused by lack of these nutrients," she says. "Until we have hard evidence, we really can't make any recommendations to consumers."