Mixed reviews

Some nutrients may prevent cataracts—or not

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, according to research done at Tufts.

Age-related cataract, the world’s leading cause of blindness, affects more than 20 million Americans over age 40. Surgery is the only known treatment, but researchers at the Jean Mayer USDA Human Nutrition Research Center on Aging sought, in three different studies, to determine if prevention is possible.

In one study, Paul Jacques, director of the Nutritional Epidemiology Program, and his colleagues analyzed the diets and examined the eyes of a group of Boston-area women over five years. Among the study participants, women who supplemented their diets with vitamin E, a powerful antioxidant, for 10 years or more had significantly less progression of cataract development. A similar decrease was found in women who had higher intakes of two of the B vitamins, riboflavin and thiamin, when compared to women with lower intakes.

“Our results,” Jacques said, “suggest that vitamin supplementation, particularly long-term use of vitamin E, may slow down cataract development.” In earlier work, Jacques and his colleagues found that vitamin C played a similar role in preventing cataracts.

However, the results weren’t as clear when the researchers looked at dietary fat. In the same population of women, the researchers found that high intakes 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 cataracts. But the results of this study, published in the American Journal of Clinical Nutrition, are not consistent with findings of other studies on the relationship between PUFAs and cataracts. In a study published in the American Journal of Epidemiology, Jacques and his colleagues observed that higher overall fat intake increased the risk of cataract development or progression, while omega-3 fatty acids, particularly those found in dark-fleshed fish, appeared to help prevent cataract formation.

“The results of these studies provide added support for a relationship between nutrient intake and cataracts,” Jacques said. “Finding ways to delay age-related cataract formation through diet or even through supplementation would enhance the quality of life for many older people.”