A subsection of the Age-Related Eye Disease Study (AREDS) supported the beneficial effects of omega-3 consumption for preventing age-related macular degeneration, the leading cause of blindness in the over 50s.
“If these results are generalizable, they may guide the development of low-cost and easily implemented preventive interventions for progression to advanced age-related macular degeneration,” wrote the researchers, led by John Paul SanGiovanni.
Eyes on AMD
AMD is a degenerative retinal disease that causes central vision loss and leaves only peripheral vision. It is the leading cause of legal blindness for people over 55 years of age in the Western world, according to AMD Alliance International.
Despite the fact that approximately 25 to 30 million people worldwide are affected by AMD, awareness of the condition is low, says the Alliance. And as the generation of Baby Boomers gets older, the Alliance expects incidence to be on the rise and triple by 2025.
There are two types of AMD – wet and dry. The former occurs when blood vessels grow abnormally beneath the macular (neovascular AMD). The blood vessels eventually leaks and the macular is scarred, obscuring vision. Dry AMD occurs when normal tissue in the macula slowly disappears. This results in a pale area of the macular called central geographic atrophy.
Increased intakes of omega-3 fatty acids may reduce the risk of both wet and dry AMD by 35 and 32 per cent, respectively, according to findings published online in the American Journal of Clinical Nutrition.
Building omega-3’s eye benefits
It is known that omega-3 fatty acids, and particularly DHA, play an important role in the layer of nerve cells in the retina, and studies have already reported that omega-3 may protect against the onset of AMD.
Indeed, a meta-analysis published in the June 2008 issue of the Archives of Ophthalmology found that a high intake of omega-3 fatty acids and fish may reduce the risk of AMD by up to 38 per cent. Scientists from the University of Melbourne in Australia reported that the benefits were most pronounced against late (more advanced) AMD, while eating fish twice a week was associated with a reduced risk of both early and late AMD.
The new study supports these earlier findings. SanGiovanni and his co-workers looked at a sub-section of 1,837 people participating in the phase 3 Age-Related Eye Disease Study (AREDS). All the participants were considered to be at a moderate-to-high risk of advanced AMD.
Over 12 years of study, the researchers found that intakes of omega-3, estimated using a food-frequency questionnaire, were related to both wet and dry AMD risk.
Indeed, participants with the highest omega-3 intakes, equivalent to about 0.11 per cent of their total energy intakes, had a 30 per cent lower risk of developing both types than people with the lowest intakes.
“The 12-year incidence of central geographic atrophy and neovascular AMD in participants at moderate-to-high-risk of these outcomes was lowest for those reporting the highest consumption of omega-3 fatty acids,” concluded the researchers.
Being an observational study, the researchers did not consider the mechanism. However, an earlier mouse study partly funded by the National Eye Institute noted lower levels of inflammatory molecules, such as prostaglandin E2 and leukotriene B4, and higher levels of anti-inflammatory molecules, such as prostaglandin D2 (American Journal of Pathology, Vol. 175, pp.799-807).
Source: American Journal of Clinical Nutrition
Published online ahead of print, doi:10.3945/ajcn.2009.27594
“Omega-3 Long-chain polyunsaturated fatty acid intake and 12-y incidence of neovascular age-related macular degeneration and central geographic atrophy: a prospective cohort study from the Age-Related Eye Disease Study”
Authors: J.P. SanGiovanni, E. Agron, A.D. Meleth, G.F. Reed, R.D. Sperduto, T.E. Clemons, E.Y. Chew