Omega-3 fats may cut macular degeneration risk.
In a case-control study of elderly male twins, men who ate at least two servings of fish per week had a significant 36% risk reduction of developing age-related macular degeneration (AMD) versus men who ate less than one serving of fish per week, after adjusting for confounding factors (Arch. Ophthalmol. 2006;124:995-1001). Omega-3 fatty acid intake was associated with a 45% AMD risk reduction when individuals in the highest and lowest quartiles of consumption were compared.
"A good source of omega-3 fatty acids is the diet, and there is an increasing trend for the addition of this nutrient to many common foods in the American diet," noted the study authors, Dr. Johanna M. Seddon of the Massachusetts Eye and Ear Infirmary, Boston, and her colleagues.
The study recruited individuals from the National Academy of Sciences-National Research Council World War II Veteran Twin Registry. Local ophthalmologists performed eye exams on the participants and took fundus photographs that were centrally developed and reviewed by graders masked to the clinical diagnosis. Participants were interviewed regarding their risk factors and they completed questionnaires detailing their eating habits and use of vitamins, supplements, and omega-3 fatty acids.
The researchers identified smoking as the risk factor most significantly associated with AMD. Compared with men who had never smoked, the incidence of AMD was nearly double in current smokers and 70% higher in former smokers. The investigators estimated that 32% of the cases of AMD in the cohort were attributable to cigarette smoking. The investigators assessed a total of 222 twins with AMD (grade 3-5 on a 5-point scale) and 459 twins without AMD (grade 1-2). Analysis of the 77 pairs of twins in which only one had AMD showed the same effects of smoking and omega-3 fatty acid intake that were observed in the overall group.
A second, longitudinal study conducted in Australia confirmed the benefit of omega-3 fatty acids for reducing the risk of age-related maculopathy (ARM).
Over a 5-year period, the incidence of ARM in adults 49 years or older was significantly associated with dietary fat intake (Arch. Ophthalmol. 2006;124:981-6). After adjustment for confounding factors, individuals in the highest quintile of fat intake--whether total fat, saturated fatty acids, monounsaturated fatty acids, or trans fat--were approximately 50% less likely to develop early ARM than individuals in the lowest quintile. Those in the highest quintile of dietary n-3 polyunsaturated fatty acids had a 59% risk reduction in early ARM versus those in the lowest quartile.
Fish consumption also appeared beneficial in preventing ARM in the longitudinal study. Individuals who ate at least one serving of fish per week were 40% less likely to develop early ARM over 5 years.
Moreover, those who ate at least three servings per week had a 75% risk reduction in late ARM.
Brian Chua of the University of Sydney (Australia), and colleagues evaluated 2,335 participants from the Blue Mountains Eye Study. Dietary questionnaires were completed at baseline, and retinal photographs were evaluated at baseline and after 5 years. The investigators defined early ARM as the presence of indistinct soft drusen, reticular drusen, or concurrent distinct soft drusen and retinal pigmentary abnormalities, while late ARM was defined as neovascular ARM or generalized atrophy involving the foveal center.
The overall incidences of early and late ARM were 7% and 1%, respectively. The investigators found no association between the incidence of ARM and consumption of butter, margarine, or nuts.
BY MELINDA TANZOLA
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|Publication:||Internal Medicine News|
|Date:||Oct 15, 2006|
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