By Margarita Nahapetyan
A diet that contains fish, nuts, olive oil and other products with omega-3 fatty acids, can significantly reduce the risk of developing eye disease known as age-related macular degeneration (AMD), according to studies from two different Australian research teams.
By 2020, as many as 3 million adults in the United Stated are expected to develop late-stage age-related macular degeneration disease, according to background information of the study. AMD is the leading cause of severe vision loss among older adults with the ages over 65 years, in the developed countries. The risk factors that have already been determined include age, genetic factors and smoking habits, which turns out to be the only consistently reported modifiable risk factor.
In the first report, Dr. Jennifer S.L. Tan, M.B.B.S., B.E., of Westmead Hospital, University of Sydney, Australia, and her colleagues analyzed the data of 2,454 individuals who took part in the Blue Mountains Eye Study in the period between 1992 and 1994. At that time, volunteers were asked to fill out a food frequency questionnaire that was analyzed at a later time in orter to establish the intake of various fatty acids by all study participants. Digital photographs of the retina were used to assess the development of AMD five and 10 years later.
After taking into consideration factors such as age, gender and smoking habits, eating one serving of fish on a weekly basis was associated with a 31 per cent lower risk of developing early macular degeneration of the eye. The link turned out to be much stronger among adults whose diet contained a lower consumption of linoleic acid, an unsaturated omega-6 fatty acid that is primarily found in vegetable oils. Consumption of between one and two servings of nuts per week was associated with a 35 per cent decreased risk of and early stage of AMD.
In the report number two, Dr. Elaine W.-T. Chong, M.D., Ph.D., M.Epi., of the Centre for Eye Research Australia, and team of researchers looked at data from 6,734 adults with the ages between 58 and 69 years. For the period between 1990 and 1994, nutrient intakes of all the participants were examined based also on a food frequency questionnaire, and they were followed for the development of the age-related disease between 2003 and 2006. The results revealed that 2,872 individuals have developed early AMD, and 88 adults have developed late AMD.
The study found that people who consumed higher levels of trans-unsaturated fats, were more likely to suffer from late AMD, while those who included the most omega-three fatty acids into their diet, had less chance to develop early AMD. "Olive oil intake (100 milliliters or more per week compared to less than 1 milliliter per week) was associated with decreased prevalence of late AMD," the authors said. There were no major associations with AMD for intakes of fish, total fat, butter or margarine. Dr. Chong and her colleagues also discovered that individuals who consumed the most trans fat were nearly 1.8 times more likely to experience late AMD during the follow-up period of the research. Trans fat is a type of fat that can be found in commercial baked goods and fried foods, is known to increase the levels of LDL, or "bad" cholesterol.
The experts concluded that their findings support the hypothesis that increased intake of omega-3 fatty acids and consumption of fish and/or nuts on a regular basis in the diet may be very beneficial and helpful against the development of early age-related macular degeneration. These fatty acids may protect the eyes by preventing the buildup of plaque in the arteries or reducing inflammation, blood vessel formation and oxygen-related cell damage in the retina. "Our findings also indicate that an appropriate balance among various nutrients is essential for maximizing nutritional benefit," the investigators wrote, and added that further studies are needed in order to find out whether changing an individual's diet or recommending supplementation could prevent or delay the development of AMD.
The findings have been published in the May issue of Archives of Ophthalmology, one of the JAMA/Archives journals.