Age-related cataract, the world's leading cause of blindness, affectsmore than 20 million Americans over the age of 40 years. Surgicalcorrection is currently the only known option for intervention, butresearchers at the Jean Mayer USDA Human Nutrition Research Center onAging at Tufts University recently sought, in three different studies,to determine if prevention is possible. Their findings suggest thatvitamins and polyunsaturated fatty acids--two categories of nutrientsbelieved 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 theNutritional Epidemiology Program at the Center, and his colleaguesanalyzed the diets and examined the eyes of a group of Boston-areawomen over the course of five years. Among the study participants, whowere all members of the larger Nurses' Health Study, women who reportedsupplementing their diets with vitamin E (a powerful antioxidant) for10 years or more had significantly less progression of cataractdevelopment at the five-year follow-up exam. A similar relativedecrease in cataract progression was seen in women who reported higherintakes of two of the B vitamins, riboflavin and thiamin, when comparedto women with lower intakes.
"Our results," says Jacques, who is also a professor at theFriedman School of Nutrition Science and Policy at Tufts, "suggest thatvitamin supplementation, particularly long-term use of vitamin E, mayslow down cataract development." These results build upon some ofJacques' earlier work. In 2001, while examining the same group ofNurses' Health Study members, Jacques and his colleagues found supportfor a similar role for vitamin C in the prevention of cataracts.
"On the other hand," says Jacques, "the results were not soclear when we looked at dietary fat." In the same population of women,Jacques and his colleagues found that high dietary intake of either orboth 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 developingcataracts in one of the three lens locations examined. The results ofthis study, which were published in the American Journal of ClinicalNutrition, are not consistent, however, with findings of other studieson the relationship between PUFAs and cataracts. In a study that wasrecently published in the American Journal of Epidemiology, Jacques andcolleagues observed that higher overall fat intake increased the riskof cataract development or progression, while omega-3 fatty acids, inparticular the types found in dark-fleshed fish, appeared to contributeto the prevention of cataract formation.
"The results of these studies provide added support for arelationship between nutrient intake and cataracts," says Jacques.However, since there is inconsistency among studies of fat intake andcataracts, he cautions that more research is needed. Jacques adds,"finding ways to delay age-related cataract formation through diet, oreven through supplementation, would enhance the quality of life formany older people, but many questions regarding the role of diet incataract prevention remain unanswered."
Jacques PF, Taylor A,Moeller S, Hankinson SE, Rogers G, Tung W, Ludovico J, Willett WC,Chylack LT. Archives of Ophthalmology. April 2005; 123:517-526."Long-term Nutrient Intake and 5-Year Change in Nuclear LensOpacities."
Lu M, Taylor A, Chylack LT, Rogers G, Hankinson SE, Willett WC,Jacques PF. American Journal of Clinical Nutrition. April 2005;81:773-779. "Dietary Fat Intake and Early Age-related Lens Opacities."
Lu M, Cho E, Taylor A, Hankinson SE, Willett WC, Jacques PF.American Journal of Epidemiology. May 15, 2005; 161(10):948-59."Prospective study of dietary fat and risk of cataract extraction amongUS women."
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