BOSTON (June 18, 2009) - Omega-3 fatty acids found in fatty fish such as tuna and salmon may protect against progression of age-related macular degeneration (AMD), but the benefits appear to depend on the stage of disease and whether certain supplements are taken, report researchers at the Laboratory for Nutrition and Vision Research (LNVR), Jean Mayer USDA Human Nutrition Research Center on Aging (HNRCA) at Tufts University.
The researchers calculated intakes of docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) from dietary questionnaires administered to 2,924 men and women, aged 55 to 80 years, participating in an eight-year supplement trial, the Age-Related Eye Disease Study (AREDS) of the National Eye Institute (NEI). The AREDS trial results suggest taking supplements of antioxidants plus zinc prevents progression of late-stage AMD. AREDS study participants were randomly allocated to receive either a placebo or supplements containing the antioxidants vitamins C and E and beta carotene, the minerals zinc and copper, or a combination of both.
"In our study, we observed participants with early stages of AMD in the placebo group benefited from higher intake of DHA, but it appears that the high-dose supplements of the antioxidants and/or the minerals somehow interfered with the benefits of DHA against early AMD progression," says senior author Allen Taylor, PhD, director of the LNVR at the USDA HNRCA. Taylor is also a professor at the Friedman School of Nutrition Science and Policy at Tufts and Tufts University School of Medicine (TUSM).
The supplements interfere with the protective effects of DHA and EPA at the early stages of AMD progression, not in the later stages.
The antioxidant supplements did not seem to interfere with the protective effects of DHA and EPA against progression to advanced stages of AMD. Participants who consumed higher amounts of DHA and EPA appeared to have lower risk of progression to both wet and dry forms of advanced AMD. The results are published on-line ahead of print in the British Journal of Ophthalmology.
A low glycemic index diet (basically sugars in forms that are slow to break down and be absorbed) provides additional protective effect.
"Data from the present study also shows the supplements and omega-3 fatty acids collaborate with low-dietary glycemic index (dGI) diets against progression to advanced AMD," says corresponding author Chung-Jung Chiu, DDS, PhD, a scientist in the LNVR and an assistant professor at TUSM. "Our previous research suggests a low-GI diet may prevent AMD from progressing to the advanced stage. We hypothesize that the rapid rise of blood glucose initiated by high-GI foods results in cellular damage that retinal cells cannot handle, thus damaging eye tissues."
Take home lesson: get more omega 3 fatty acids in your diet. Also, learn how to eat a low glycemic index diet. Also, the benefits of antioxidant vitamins are overrated.
Professor Chakravarthy, who is also a Consultant Ophthalmic Surgeon at the Royal Hospital in Belfast, said: "Late AMD causes severe sight loss and has a huge economic impact both in terms of the effects of sight loss itself and in terms of the expensive treatments that are needed to deal with the condition.
"Up to 500 people a year in Northern Ireland will lose sight in one or both eyes as a result of late AMD.
"We wanted to carry out the study as prevention of progression to late AMD can result in a reduced financial and societal burden."
As the macula of the eye is very rich in antioxidants the researchers wanted to see if a supplement called CARMA (Caroteneoids and Co-antioxidants in Age-related Maculopathy) containing the carotenoids lutein and zeaxanthin could help slow down AMD.
The supplement also contained vitamins C,E and Zinc, which had been used in a previous study.
The latest study showed that intake of high levels of both carotenoids preserved the macular pigments, slowing down the progression from early AMD to late AMD.
|Share |||Randall Parker, 2009 June 18 07:54 AM Aging Diet Eye Studies|