Omega-3 fatty acid and fish intake prevents AMD
Omega-3 fatty acid and fish intake prevents AMD
Wednesday, March 30, 2011
Dietary intake of omega-3 fatty acids and fish decreases the risk of early age-related macular degeneration (AMD) in women, according to a new study.
Cardiovascular disease and AMD have been hypothesized to share similar mechanisms and risk factors. Dietary intake of fish, and specifically omega-3 fatty acids concentrated in fish (docosahexaenoic acid [DHA] and eicosapentaenoic acid [EPA]), has been linked with reduced rates of cardiovascular events in epidemiologic studies and could have a similar beneficial effect in AMD. Omega-3 fatty acids are known to exert anti-inflammatory, anti-atherosclerotic, and antithrombotic effects on the vasculature and may help to maintain or improve choroidal blood flow in the eye.
Some evidence from observational epidemiologic studies suggests an inverse relation between regular dietary intake of fish and DHA and EPA and risks of advanced AMD. Indeed, the Age-Related Eye Disease Study 2 (AREDS-2) is evaluating in a randomized trial whether supplemental DHA and EPA can reduce the risk of progression to advanced AMD. However, available data for early AMD are limited and inconsistent.
Methods and Results
Study participants were women enrolled in the Women's Health Study, a completed randomized trial of low-dose aspirin and vitamin E in the primary prevention of cardiovascular disease and cancer.
A detailed food-frequency questionnaire was administered at baseline among 39,876 female health professionals (mean age: 54.6 years). A total of 38,022 women completed the questionnaire and were free of a diagnosis of AMD. The main outcome measure was incident AMD responsible for a reduction in best-corrected visual acuity to 20/30 or worse based on self-report confirmed by medical record review.
A total of 235 cases of AMD, most characterized by some combination of drusen and retinal pigment epithelial changes, were confirmed during an average of 10 years of follow-up. Women in the highest tertile of intake for docosahexaenoic acid, compared with those in the lowest, had a multivariate-adjusted relative risk of AMD of 0.62. For eicosapentaenoic acid, women in the highest tertile of intake had a relative risk of 0.66. Consistent with the findings for docosahexaenoic acid and eicosapentaenoic acid, women who consumed 1 or more servings of fish per week, compared with those who consumed less than 1 serving per month, had a relative risk of AMD of 0.58.
Discussion and Conclusions
In this large prospective cohort study of female health professionals, regular consumption of DHA and EPA and fish was associated with a 35% to 45% lower risk of visually significant AMD during 10 years of follow-up. This inverse association was independent of other AMD risk factors. The study population comprised women without a prior diagnosis of AMD, and the large majority of cases documented during follow-up were characterized by some combination of drusen and RPE changes signifying an early stage of disease development. Thus, these findings suggest that dietary intake of DHA and EPA and fish may be beneficial in the primary prevention of AMD.
Previous observational studies, including 5 prospective studies, are suggestive of an inverse association between fish and omega-3 long-chain fatty acid intake and risks of advanced AMD (ie, neovascular AMD or central geographic atrophy). However, the data for early AMD are more limited and inconsistent. Of 5 cross-sectional studies that included cases of early AMD, 3 reported an inverse relation with advanced AMD only, and 2 reported no association with either early or advanced AMD.
The findings of this study, based on 10 years of follow-up of a large cohort of female health professionals, are broadly consistent with earlier findings and appear to be the strongest observational evidence to date in support of a possible role for intake of omega-3 long-chain fatty acids and fish in the primary prevention of AMD. Moreover, because early AMD is associated with an increased risk of developing advanced AMD (eg, 1 study showed that eyes with soft indistinct drusen or RPE abnormalities were approximately 20 to 40 times more likely to develop late AMD than were eyes without these lesions), dietary intake of omega-3 long-chain fatty acids and fish by persons at usual risk may ultimately reduce the number of persons who have advanced AMD.
In summary, 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. This study is the strongest evidence to date to support a role for omega-3 long-chain fatty acids in the primary prevention of AMD.
WHAT IT MEANS TO YOU: DHA and EPA are the "active ingredients" of fish oil. This study finds that greater dietary intake of fish oil, or eating fish at least once per week, can help prevent the onset of AMD. This finding is significant because most research focuses on ways to slow the progression of AMD among those that already have the disease. We have much less information regarding what can help prevent the onset of AMD among normal health individuals. This study provides strong support for the practice of recommending fish oil supplementation and/or fish consumption as a means of avoiding AMD.
Source: Arch Ophthalmol. 2011 Mar 14. [Epub ahead of print]
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