Tuesday, May 14, 2013
Fish Oil Doesn't Seem to Help Age-Related Macular Degeneration
A large-scale National Eye Institute study has shown fish oil supplements containing omega-3 fatty acids do not alter the progression of age-related macular degeneration, says a national team of researchers including David M. Brown, M.D., an retina specialist at The Methodist Hospital who ran Houston's part of the study.
Another key finding of the Age-Related Eye Disease Study 2, or AREDS 2, is that lutein and zeaxanthin may be safer than beta-carotene in reducing risk of disease progression.
"If you look at all the analysis performed in the AREDS 2 study, it looks like lutein taken with zeaxanthin is at least as effective and may be better than beta-carotene," Brown said. "If you also consider that beta-carotene was associated with increased lung cancer rates in all former smokers, I no longer recommend any formulations containing beta-carotene."
Researchers saw a modest decrease in the development of age-related macular degeneration (AMD) among those who took high amounts of zinc, but that result was not statistically significant.
"Millions of older Americans take nutritional supplements to protect their sight without clear guidance regarding benefit and risk," said NEI director Paul A. Sieving, M.D., Ph.D. "This study clarifies the role of supplements in helping prevent advanced AMD, an incurable, common, and devastating disease that robs older people of their sight and independence."
Like beta-carotene, lutein and zeaxanthin can be converted to vitamin A in humans and can collect at the retina, where they probably limit chemical damage caused by light. Lutein is found in foods like egg yolk and animal fat deposits. Zeaxanthin is found in some berries, corn, and paprika.
AREDS 2's results agree with past studies that have shown an association between beta-carotene consumption and the development of lung cancer in current or former smokers. About half of AREDS 2 participants reported having been smokers at some point in their lives.
Macular degeneration is a disease in which retina damage causes a loss of visual acuity in the center of the eye, called the macula. AMD is a major cause of blindness in the elderly, and currently affects about 11 million Americans. National Eye Institute experts believe that number will double by 2050.
About 12 years ago, the National Eye Institute began funding studies to look at how diet and dietary supplements affect the progression of the disease. AREDS showed a 25 percent decreased risk of AMD when study participants took vitamin C, beta-carotene (a precursor to vitamin A), vitamin E, zinc, and copper (called the AREDS Formulation).
The five-year AREDS 2, which began in 2006, was a national study of more than 4,200 people. It suggests fish oil supplements probably do not need to be added to the formulation, and that lutein with zeaxanthin might replace beta-carotene in the AREDS Formulation, since lutein is not associated with increased risk for lung cancer.
"The first AREDS study showed us that vitamins really make a difference in decreasing the complications of AMD," Brown said. "Now with the AREDS 2, we have solid data on what to recommend to our patients. Based on the AREDS 2 data, I now recommend that my patients no longer take beta-carotene but look for a vitamin with 10 mg Lutein, 2 mg zeaxanthin, 80mg zinc, 2mg copper, 500mg vitamin C, and 400 IU vitamin E."