Nutrition scientists take a look at cataract prevention

The latest information coming from the Friedman School of Nutrition Science and Policy at Tufts University

Age-related cataract, the world’s leading cause of blindness, affects more than 20 million Americans over the age of 40 years. Surgical correction is currently the only known option for intervention, but researchers at the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University recently sought, in three different studies, to determine if prevention is possible. Their findings suggest that vitamins and polyunsaturated fatty acids–two categories of nutrients believed to have health benefits–may both affect cataract development, although not necessarily in beneficial ways.

In one study, lead scientist Paul Jacques, DSc, director of the Nutritional Epidemiology Program at the Center, and his colleagues analyzed the diets and examined the eyes of a group of Boston-area women over the course of five years. Among the study participants, who were all members of the larger Nurses’ Health Study, women who reported supplementing their diets with vitamin E (a powerful antioxidant) for 10 years or more had significantly less progression of cataract development at the five-year follow-up exam. A similar relative decrease in cataract progression was seen in women who reported higher intakes of two of the B vitamins, riboflavin and thiamin, when compared to women with lower intakes.

“Our results,” says Jacques, who is also a professor at the Friedman School of Nutrition Science and Policy at Tufts, “suggest that vitamin supplementation, particularly long-term use of vitamin E, may slow down cataract development.” These results build upon some of Jacques’ earlier work. In 2001, while examining the same group of Nurses’ Health Study members, Jacques and his colleagues found support for a similar role for vitamin C in the prevention of cataracts.

“On the other hand,” says Jacques, “the results were not so clear when we looked at dietary fat.” In the same population of women, Jacques and his colleagues found that high dietary intake of either or both an omega-6 polyunsaturated fatty acid (PUFA) found in sunflower, safflower, corn, and soybean oils, and an omega-3 PUFA found in canola, flaxseed, and soybean oils, may increase the risk of developing cataracts in one of the three lens locations examined. The results of this study, which were published in the American Journal of Clinical Nutrition, are not consistent, however, with findings of other studies on the relationship between PUFAs and cataracts. In a study that was recently published in the American Journal of Epidemiology, Jacques and colleagues observed that higher overall fat intake increased the risk of cataract development or progression, while omega-3 fatty acids, in particular the types found in dark-fleshed fish, appeared to contribute to the prevention of cataract formation.

“The results of these studies provide added support for a relationship between nutrient intake and cataracts,” says Jacques. However, since there is inconsistency among studies of fat intake and cataracts, he cautions that more research is needed. Jacques adds, “finding ways to delay age-related cataract formation through diet, or even through supplementation, would enhance the quality of life for many older people, but many questions regarding the role of diet in cataract prevention remain unanswered.”