Supplements and Dietary Change Make a Difference in Age-Related Macular Degeneration

Dr. Harriott's Comments:
This study acknowledges that modest levels of omega 3 fatty acid intake and a low glycemic diet are beneficial for AMD. It then shows, however that,concurrent supplementation with anti-oxidants like C, E, etc may necessitate higher levels of consumption of omega 3 fatty acids to maintain the benefit in earlier stages of the disease.

Take home message would be that omega 3 fatty acid supplements (these fatty acids are found in flax oil, walnut oil, fish oil, among other sources) are a good thing. Also, a low glycemic load diet is once again shown to be a clear path to healthy living. And lastly, if you have early stage AMD, additional anti-oxidant supplementation may interfere with the benefits of omega 3 fatty acids for that disease. Further study will be necessary to come up with specific dietary recommendations for AMD.

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Other Factors May Affect Link Between Omega 3s and AMD
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LITTLE FALLS, N.J., June 19 -- The association between omega-3 fatty acids and lower risk of age-related macular degeneration (AMD) appears to be modified by other dietary supplements and disease stage, researchers found.

As expected, high intake of the omega-3s docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) was associated with a lower risk of progression to advanced AMD in a secondary analysis of a randomized trial, Chung-Jung Chiu, DDS, PhD, of Tufts University in Boston, and colleagues reported online in the British Journal of Ophthalmology.

For early AMD progression, however, the apparent protective effect of DHA was eliminated in patients taking supplements containing high doses of antioxidants, zinc, or both as part of the Age-Related Eye Disease Study.

"The present study adds additional support to the idea that diet and, if necessary, supplementation can be optimized for the prevention of AMD," the researchers said.

The original research showed that high doses of antioxidants protected against the progression of advanced age-related macular degeneration. (See High Antioxidant Diet May Delay Age-Related Macular Degeneration)

A number of other studies have also identified a link between high consumption of omega-3 fatty acids and a reduced risk of AMD, and some evidence points to a protective effect of a low glycemic index diet.

However, it had remained unclear how all of these dietary factors interacted, the researchers said.

So they performed an analysis of data from 2,924 patients participating in the Age-Related Eye Disease Study, an eight-year supplementation trial. Dietary intake was assessed using food-frequency questionnaires.

There were four arms in the trial: placebo, antioxidant supplementation with vitamins C and E and beta-carotene, supplementation with zinc, or combined supplementation.

The highest intakes of DHA (HR 0.73, 95% CI 0.57 to 0.94) and EPA (HR 0.74, 95% CI 0.59 to 0.94) and the diets lowest in glycemic index (HR 0.76, 95% CI 0.60 to 0.96) were linked to lower risk for progression to advanced AMD, independent of the type of supplementation.

There were significant interactions between dietary glycemic index and both DHA (P=0.0003) and EPA (P=0.0001) intake, such that patients who had low glycemic index diets and high consumption of the omega-3 fatty acids had lower risks of progression to advanced AMD than patients with high intakes alone.

Patients in the early stages of AMD, however, only derived a benefit from consuming large amounts of DHA if they were not taking additional supplementation as part of the study (HR 0.58, 95% CI 0.37 to 0.92).

"It appears that the high-dose supplements of the antioxidants and/or the minerals somehow interfered with the benefits of DHA against early AMD progression," said study co-author Allen Taylor, PhD, also of Tufts.

The levels of DHA and EPA consumed in the study were much lower than the recommended intake, according to the researchers.

To hit the target, individuals could consume two to three servings of cold-water fatty fish, such as salmon, tuna, mackerel, sardines, and herring, as well as shellfish.

However, it would be premature to make specific dietary recommendations for patients with AMD, the researchers said.

"Taken together, these data indicate that consuming a diet with higher levels of omega-3 fatty acids, antioxidants, and low-glycemic index foods may delay compromised vision due to AMD," Dr. Taylor said.

"The present study adds the possibility that the timing of a dietary intervention as well as the combination of nutrients recommended may be important," he said.

The study was funded by the U.S. Department of Agriculture, the NIH, the Johnson & Johnson Focused Giving Program, the American Health Assistance Foundation, and the Ross Aging Initiative.

The authors reported that they had no conflicts of interest.

Primary source: British Journal of Ophthalmology
Source reference: Chiu C-J, et al "Does eating particular diets alter risk of age-related macular degeneration in users of the age-related eye disease study supplements?" Br J Ophthalmol 2009; DOI: 10.1136/bjo.2008.143412.