Vitamins Linked to Cataract Prevention; Role of Fats Less Clear

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NEW TUFTS RESEARCH SUGGESTS that vitamin supplements, particularly long-term use of vitamin E, may slow the development of cataracts. Lead scientist Paul Jacques, DSc, director of the Nutritional Epidemiology Program at the Jean Mayer USDA Human Nutrition Research Center on Aging, and his colleagues analyzed the diets and examined the eyes of 408 women, ages 52 to 74, over five years. Participants who reported having supplemented their diets with vitamin E for at least 10 years showed significantly less progression of cataract development. A similar relative decrease in cataract progression was seen in women who reported higher intakes of two of the B vitamins, riboflavin and thiamin, compared to those with lower intakes.

The study, published in the journal Archives of Ophthalmology, looked at women taking part in the larger Nurses' Health Study. The results build upon some of Jacques' earlier work with the same group of Nurses' Health Study members: In 2001, the Tufts researchers found support for a similar role for vitamin C in the prevention of cataracts. Both vitamin C and vitamin E have drawn research attention for their antioxidant effects.

In a pair of other recently published studies of the same group of women, the scientists also looked for links between polyunsaturated fat intake and cataract development. Here the conclusions are less clear-cut, however.

In a study published in the American Journal of Clinical Nutrition, Jacques and his colleagues studied high dietary intake of both linoleic acid (an omega-6 polyunsaturated fatty acid found in sunflower, safflower, corn and soybean oils) and an omega-3 fatty acid found in canola, flaxseed and soybean oils. The results showed that a high intake of either of these fats may increase cataract risk in one of the three lens locations examined.

A study published in the American Journal of Epidemiology, in which cataract development was assessed over a longer, 13-15-year period, also connected high linoleic-acid consumption with increased risk of cataract development or progression. But in this study Jacques and colleagues found that the omega-3 fatty acids in dark-fleshed fish appeared to help prevent cataract formation--although the omega-3s found in oils did not.

"The studies are not completely consistent, but they are also not necessarily contradictory," says Jacques. "The results of these studies provide added support for a relationship between nutrient intake and cataracts, but more research is needed."

Age-related cataracts, the world's leading cause of blindness, affect more than 20 million Americans over the age of 40. Surgical correction is currently the only known option for intervention against cataracts.

"Many questions regarding the role of diet in cataract prevention remain unanswered," Jacques notes. But he 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."

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