Do High-Fat Diets Cause Blindness?

Age-related macular degeneration (AMD) is a deterioration of the central portion of the retina and the number one cause of blindness in the U.S. Unlike cataracts, there is no effective treatment for most people with AMD. Its prevalence increases dramatically with age. By age 70 to 75 years, more than 75% of Americans have AMD and nearly one-third show early signs of the disease. Smoking, low intakes of antioxidant nutrients and zinc also seem to increase the risk of developing AMD. One study showed that supplements of zinc, vitamins C & E and beta carotene were able to slow the progression of advanced AMD but had no effect on early signs of the disease.

A prospective study of diet and AMD using data from the Nurses’ Health Study found a 54% increased relative risk of developing AMD for the highest quintile of fat intake compared to the lowest.1 This study also found that an increased intake of linolenic acid was associated with increased risk whereas an increased intake of the longer-chain omega 3 fatty acids was associated with a reduced risk of AMD. Similar findings were observed in a multicenter, case-control study of 349 subjects with AMD. Compared to 504 subjects with eye disease but no signs of AMD, those with AMD were found to have a higher intake of fat. After correcting for smoking and other risk factors, a greater intake of vegetable fat, including both polyunsaturated fat and monounsaturated fat was associated with a more than 2-fold increased risk for advanced AMD. As with the data from the Nurses’ Heart study, the results of this study also showed that an increased intake of fish and long-chain omega-3 fatty acids was associated with a reduced chance of developing AMD.2

Bottom Line: The results of these two studies suggest that those interested in reducing their risk of developing AMD should reduce their intake of both polyunsaturated and monounsaturated vegetable oils and consume more fish rich in omega-3 fatty acids. There is insufficient evidence to recommend the use of supplements of antioxidant nutrients or zinc as a means of reducing the risk of developing AMD. However, those with advanced AMD should discuss the use of these supplements with their eye doctor as these supplements have shown some promise for slowing the progression of advanced AMD.

By Dr. James J Kenney, PhD, FACN

References:

1. Am J Clin Nutr 2001;73:209-18

2. Arch Opthalmol 2001;119:1191-99