A meta-analysis of nine previously published studies has found that eating fish and other foods high in omega-3 fatty acids may significantly cut the risk of developing the eye disease age-related macular degeneration (AMD).
However, the researchers say that the accumulated evidence includes few clinical trials and is insufficient to support the routine consumption of such foods for AMD prevention.
"Age-related macular degeneration (AMD) is the leading cause of severe vision loss among elderly people," the authors write as background information in the article.
New treatments for AMD are potentially risky and treat only certain forms of the disease.
"Thus, primary prevention of AMD by modifying risk factors (e.g., cigarette smoking) remains an important public health strategy," they add.
For the study, Elaine W-T. Chong, M.B.B.S., of the University of Melbourne, Australia, and colleagues conducted a systematic review of studies published before May 2007 evaluating the fish consumption and overall omega-3 fatty acid intake for the prevention of AMD. A total of nine studies were identified with 88,974 participants, including 3,203 individuals with AMD.
When results from all nine studies were combined, a high dietary intake of omega-3 fatty acids was associated with a 38 percent reduction in the risk of late (more advanced) AMD, while eating fish twice a week was associated with a reduced risk of both early and late AMD.
"Long-chain omega-3 fatty acids, docosahexaenoic acid in particular, form an integral part of the neural retina," the layer of nerve cells in the retina, the authors write.
Outer cells of the retina are continually shed and regenerated, and deficiencies of omega-3 fatty acids may therefore initiate AMD.
"A diet rich in omega-3 fatty acids and fish, as a proxy for long-chain omega-3 fatty acid intake, has therefore been hypothesized as a means to prevent AMD," they write.
"Although this meta-analysis suggests that consumption of fish and foods rich in omega-3 fatty acids may be associated with a lower risk of AMD, there is insufficient evidence from the current literature, with few prospective studies and no randomized clinical trials, to support their routine consumption for AMD prevention," they conclude.
The study is published in the June issue of Archives of Ophthalmology, one of the JAMA/Archives journals.