January 2008

 

RETINA

 

Omega-3’s & AMD


by Christine Hamel EyeWorld Contributing Editor

   

Newest report from the AREDS Research Group shows the potentially positive influence of omega-3 intake

Dietary omega-3 fatty acids have long been suspected of playing an important biological role in influencing the development and progression of age-related macular degeneration (AMD). Reinforcing this theory, the twentieth report by the Age-Related Eye Disease Study (AREDS) Research Group in a recent issue of the Archives of Ophthalmology detailed the results of an observational study showing the association between a higher intake of omega-3 long-chain polyunsaturated fatty acid and a decreased likelihood of having neovascular AMD.

According to Emily Y. Chew, M.D., deputy director of epidemiology and clinical research, National Eye Institute, Bethesda, Md., and one of the members of the AREDS Research Group, this study is the largest of its kind. “We have more cases than most of the other studies. The other studies were population-based studies and had a very small number of [cases of] advanced macular degeneration,” said Dr. Chew. “We have by far the largest number of patients … because the clinical trial recruited these advanced cases specifically.”

Recruiting patients from 11 retinal specialty clinics, AREDS enrolled 4,519 participants between 1992 and 1998 who were aged 55 to 80 years. While 3,640 patients had either AMD or were at high risk of developing the disease, the others had no AMD. Participants were required to be free of advanced AMD in at least one eye. Upon enrollment in the study, participants were surveyed about their eating habits by using a self-administered, 90-item food frequency questionnaire that asked about intake of foods with commonly consumed sources of various nutrients, including lipids, that are thought to have the potential to influence AMD. Participants were asked how often on average during the past year that they had consumed each listed type of food or beverage. The study compared participants in the highest quintile of lipid intake with those in the lowest quintile. After the analyses adjusted for total energy intake and nutrient- and nonnutrient-based predictors and correlates, the study found that there was an inverse association between the presence of neovascular AMD and intake of dietary omega-3 long-chain polyunsaturated fatty acid (odds ratio [OR], 0.61; 95% confidence interval [CI], 0.41–0.90) and intake of docosahexaenoic acid, a retinal omega-3 long-chain polyunsaturated fatty acid (OR, 0.54; 95% CI, 0.36–0.80). Also, of interest, the study found that more than two medium servings of fish per week was associated with lower odds of neovascular AMD (OR, 0.61; 95% CI, 0.37–1.00). Four ounces of broiled or baked fish more than once per week also lessened the risk of participants having neovasular AMD (OR, 0.65; 95% CI, 0.45–0.93). Dietary arachidonic acid, an omega-6 fatty acid found in red meat, was directly associated with the prevalence of neovasular AMD (OR, 1.54; 95% CI, 1.04–2.29). Other lipids were not found to have a statistically significant relationship in the AMD groups.

However, although these study findings are suggestive, Dr. Chew cautioned that they are just observational. “We can’t be certain that eating fish will actually reduce your risk of age-related macular degeneration,” said Dr. Chew. “We can’t be sure that there isn’t something different about the people who eat fish and the people who don’t eat fish. Are they taking better care of themselves? Are they people who can afford fish, because fish is expensive? Are they different in other ways?” Dr. Chew notes that further research is needed in order to draw definite conclusions. “Our next study, AREDS2, is looking at omega-3, so we’re actually testing that now in a clinical trial.” Through randomized control trials, the AREDS has previously shown that persons with at least a moderate risk of developing advanced AMD lowered their risk of developing this disease by about 25% when they were given a high dosage of a combination of zinc and antioxidants (vitamin C, vitamin E, and beta carotene). The next step will be to perform another randomized control trial in order to further investigate the influence of dietary omega-3 fatty acids on AMD. In this trial, the intervention group will be given one gram of omega-3 fatty acids and/or 10 mg of lutein/2 mg of zeaxanthin per day. “We began in earnest December of last year, and we have over 3,000 participants enrolled in the study now,” said Dr. Chew.

“We won’t have results [from the omega-3 trial] for another five or six years,” said Dr. Chew. “It seems to make good general sense to maintain a good diet and have moderation in all things … but certainly we don’t recommend that people go out and take fish oil at this point, because we don’t know whether or not that does anything. Only the randomized trial can give us the results to that.”

Editor’s note: Dr. Chew does not have any financial interests related to her comments.

Contact Information

Chew: 301-496-6583, echew@nei.nih.gov

       
Omega-3’s & AMD Omega-3’s & AMD
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