A new study conducted by scientists at Brigham and Women’s Hospital and Divisions of Harvard Medical School and Harvard School of Public Health, Boston, found that regular consumption of fish and omega-3 fatty acids contained in fish is associated with a significantly reduced risk of developing age-related macular degeneration in women. Those who ate the most canned tuna fish and dark-meat fish decreased their risk the most. A report of the study was posted online today in JAMA’s Archives of Ophthalmology, and the full study will appear in the June issue of Archives of Ophthalmology, a Journal of JAMA.
Macular Degeneration is a significant concern as a person ages. “An estimated nine million U.S. adults aged 40 years and older show signs of age-related macular degeneration (AMD),” according to the study. Of these, 1.7 million with advanced AMD may be suffering with severe vision loss. Another 7.3 million with early AMD may have moderate or no vision loss, but are at increased risk of progressing to advanced AMD. “For the large majority of persons with early or no AMD, there is no recognized means of disease prevention other than avoiding cigarette smoking. Thus, the identification of means to prevent or delay the development of AMD would have marked public health significance,” according to the authors of the new study.
The study’s lead author, William G. Christen, Sc.D., of Brigham and Women’s Hospital and Harvard Medical School and his colleagues at Divisions of Harvard Medical School and Harvard School of Public Health, Boston, analyzed data collected as part of the Women’s Health Study, on 38,022 women health professionals, aged 45 years and older. At the start of the study in 1993, none of the women had been diagnosed with age-related macular degeneration (AMD), and none had a history of cardiovascular disease, cancer, or other major illnesses.
At the beginning of the study, the women filled out a detailed questionnaire, including information on intake of docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) (which are Omega-3 fatty acids found in fish), and arachidonic acid and linoleic acid (omega-6 fatty acids). The questionnaire collected information on the women’s average consumption of various types of foods over the past year, including detailed questions on their consumption of various types of fish, and the amount and frequency with which they ate each type of fish. There were questions on intake of canned tuna fish (3-4 oz); dark-meat fish such as mackerel, salmon, sardines, blue fish and swordfish (3-5 oz.); shrimp lobster and scallops; and other fish (3-5 oz.), as a main dish. For each fish, there were 9 possible responses, ranging from “never or less than once per month” to “6 or more times per day.”
During ten years of follow-up, additional questionnaires tracked the women’s eye health, with specific focus on diagnosis of age-related macular degeneration (AMD). Over this 10 year follow-up period, 235 cases of age-related macular degeneration (AMD) were reported. Medical records were examined for 85.2% of the women who reported a diagnosis of AMD, which was measured as “significant enough to cause the best-corrected visual acuity to be reduced to 20/30 or worse.”
The study found that “regular consumption of DHA and EPA [the Omega-3 fatty acids found in fish] and fish was associated with a 35% to 45% lower risk of visually significant AMD during 10 years of follow-up.”
The Analysis found that women who consumed the most DHA compared with those who consumed the lowest amount had a 38% lower risk of developing AMD, and similarly, those who consumed the most EPA had a 36% lower risk of AMD than those who consumed the least EPA.
Results for fish intake showed that “Consumption of 1 or more servings of fish per week, compared with less than 1 per month, was associated with a 42% lower risk of AMD.” Interestingly, “[t]his lower risk appeared to be due primarily to consumption of canned tuna fish .. and dark-meat fish,” according to the researchers. The results showed that those who consumed 1 or more servings of canned tuna or dark meat fish per week had a 44% lower risk of AMD than those who ate less than 1 serving per month.
These findings held when controlled and adjusted for other potential factors, including smoking, alcohol use, body mass index (weight), post menopausal hormone use, history of hypertension, history of high cholesterol, history of diabetes mellitus, multivitamin use, and history of an eye examination in the last 2 years.
As potential explanations of why consumption of Fish and Omega-3 Fatty Acids may be associated with reduced risk of age-related macular degeneration (AMD), the study’s authors observed that DHA and EPA (the Omega-3 Fatty Acids in fish) “could affect AMD occurrence by modulating inflammatory and immune processes thought to play a role in AMD pathogenesis.” They also postulated that, “Other mechanisms through which DHA and EPA may contribute to a reduced risk of AMD include enhanced production of resolvins and neuroprotectins, which are thought to dampen and resolve inflammatory responses.”
The authors also observed that “Cardiovascular disease and AMD have been hypothesized to share similar mechanisms and risk factors. Dietary intake of fish, and specifically w-3 fatty acids concentrated in fish.., has been linked with reduced rates of cardiovascular events in epidemiologic studies, and could have a similar beneficial effect in AMD. w-3 Fatty acids are known to exert anti-inflammatory, anti-atherosclerotic, and antithrombotic effect on the vasculature and may help to maintain or improve choroidal blood flow in the eye.”
According to the study report, previous studies have found significantly lower risk of progressing from early stage AMD to advanced AMD in those who consumed more Omega-3 fatty acids in fish. But, until this new study, researchers have not found conclusive support for an association between eating fish and Omega-3′s and lowering the risk of getting AMD in the first place. The results of this new study are therefore significant, in suggesting for the first time a possible means of preventing AMD. Since those who contract early stage AMD have an increased risk of progressing to advanced AMD and severe vision loss, preventing early stage AMD is very important.
The study authors conclude, “In summary, these prospective data from a large population of women with no prior diagnosis of AMD indicate that regular consumption of DHA and EPA and fish significantly reduced the risk of incident AMD. These data appear to be the strongest evidence to date to support a role for w-3 long-chain fatty acids in the primary prevention of AMD.”
The study was supported by research grants from the National Institutes of Health.
See the online report of the new study in the March 14, 2011 online version of » JAMA – Archives of Ophthalmology.
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