Animal Testing: Fatty Acids & AMD
A diet high in omega-3 fatty acids has been found to protect against a variety of diseases including atherosclerosis and Alzheimer’s disease. Retrospective studies have suggested that diets high in fish oil or omega-3 fatty acids may also contribute to protection against age-related macular degeneration.
A group of researchers led by Dr. Chi-Chao Chan at the National Eye Institute examined the direct effect of omega-3 fatty acids on a mouse model of age-related macular degeneration. A diet with high levels of omega-3 fatty acids resulted in slower lesion progression, with improvement in some lesions. These mice had lower levels of inflammatory molecules and higher levels of anti-inflammatory molecules, which may explain this protective effect.
The researchers suggest that “a diet enriched in EPA and DHA can reduce the progression of retinal lesions in their mouse model of age-related macular degeneration” and that “the results in these mice are in line with the epidemiological studies of age-related macular degeneration risk reduction by long chain n-3 fatty acids.” The results “further provide the scientific basis for the application of omega-3 fatty acids and their biologically active derivatives in the prevention and treatment of age-related macular degeneration.”
Long Chain Fatty Acids
A study published in the Journal of Lipids Research looked into the roles played by both long chain and very long chain polyunsaturated fatty acids (LC-PUFAs and VLC-PUFAs), both of which are naturally present in the eyes. There are not a lot of VLC-PUFAs in the eyes, and they have not received a lot of scientific attention, but this study focused on the important role they play in eye health.
Researchers concluded that a lack of either LC-PUFAs and VLC-PUFAs can lead to macular degeneration. Source: http://www.lef.org
Fish oil is the key source of these compounds.
Good versus Bad Fats: 2 Studies
In the first study, Australian researchers evaluated data from 2,454 participants in the Blue Mountain Eye Study of men and women aged 49+. Those who consumed at least one fish serving weekly had a 31 percent lower adjusted risk of developing early AMD compared with those who consumed less.
In another study, Australian researchers of the Centre for Eye Research Australia and her associates evaluated data from 6,734 men and women aged 58 to 69 who participated in the Melbourne Collaborative Cohort Study. Dietary questionnaires completed between 1990 and 1994 were analyzed for the intake of various foods and individual fatty acids. Follow up examinations conducted between 2003 and 2006 detected 2,872 cases of early age-related macular degeneration and 88 cases of late disease.
Patients whose diets included many trans-unsaturated fats experienced a marked increase in late macular degeneration incidence, while those with amounts of trans-fats in their diets in the top 25% of all the people evaluated had 76 percent greater risk than those whose trans-fat consumption was among the lowest fourth.
Olive oil was found to provide protection against late developing AMD. Comparing patients who included at least 100 milliliters olive oil weekly to those who consumed less than 1 milliliter per week, these “high olive oil users” had 52 percent lower risk of late AMD.
For early developing AMD, those people who had the highest 25 percent inclusion of omega-3 fatty acids in their diet had a 15 percent lower risk as compared with those patients who had the least consumption of omega-3 fatty acids (lowest 1/4 of consumption).
Fish as Omega-3 Source
Researches established that one serving of omega-3 fatty acid-rich fish in the diet weekly may reduce AMD risk by over 50 percent.
The EUREYE study was a population-based survey of risk factors for AMD and ARM in elderly Europeans. 2,275 people aged 65+ were given eye exams and completed a questionnaire about their diet. One aspect of the research looked at the quantity of oily fish, which is known to be high in omega-3 fatty acids. They found that 64% of the group ate less than one serving of oily fish per week; 25% of the group ate 1 serving weekly, and twice or more weekly by 12% of the survey group.
The 25% consuming oily fish at least 1 time a week were 50% less likely to develop neovascular AMD and those eating twice a week had a 58% lower risk.
Good choices for fish rich in omega-3 fatty acids are cold water fish such as salmon, herring, anchovies, mackerel and sardines.
Source: Augood, et al; Oily fish consumption, dietary docosahexaenoic acid and eicosapentaenoic acid intakes, and associations with neovascular age-related macular degeneration; American Journal of Clinical Nutrition, Vol. 88, No. 2, 398-406, August 2008.
High Omega-3 and Low Carbohydrate Diet
Researchers from Tufts University have found that a diet rich in omega-3 fatty acids and low in starchy carbohydrates can significantly reduce the risk of age-related macular degeneration (AMD).
The study, published in the journal Ophthalmology, is the first to calculate the combined effect of specific dietary nutrients and eating habits on a person’s risk for age-related macular degeneration.
During the study of 4003 participants in the ongoing Age-Related Eye Disease Study (AREDS), each dietary factor was assigned a percentile score; these scores were accumulated to find each participant’s compound score. The compound score was then evaluated for its association with the risk of AMD.
Researchers showed that vitamins C and E, zinc, lutein, zeaxanthin and the omega-3 fatty acids known as D.H.A. and E.P.A. were linked to lower risk for AMD.
The lowest risk of AMD was found in participants who regularly consumed a combination of these nutrients as part of a low-glycemic index diet.
The glycemic index (GI) is a measure of the effects of carbohydrates on blood glucose levels. Carbohydrates that break down rapidly during digestion, such as white bread and pastries, have a higher GI, as they release glucose into the bloodstream rapidly. Foods that break down more slowly, such as vegetables and proteins, have a lower GI value.
SOURCE: “Dietary Compound Score and Risk of Age-Related Macular Degeneration in the Age-Related Eye Disease Study”, Chiu, et al, Ophthalmology, Volume 116, Issue 5, Pages 939-946.
Omega-3, Nuts, Linoleic Acid and AMD
Researchers have released a new study showing that regularly including fish, omega-3 polyunsaturated fatty acids, and nuts in one’s diet helps protect against age-related AMD.
The study, published in the Archives of Ophthalmology, assessed the relationship between dietary fatty acids and the 10-year incident of AMD.
Scientists examined 3654 elderly Australian participants at baseline and re-examined 2454 of these participants five and/or ten years later. Participants completed a food frequency questionnaire.
The findings confirmed many previous studies on AMD. After adjusting for age, sex, and smoking:
- one serving of fish per week was associated with reduced risk of early AMD primarily among participants with less than the median linoleic acid consumption
- findings were similar for consumption of long-chain omega-3 polyunsaturated fatty acids: one to two servings of nuts per week was associated with reduced risk of early AMD
- a positive tie between nut consumption and reduced risk of pigmentary abnormalities were seen among nonsmokers, participants with less than the median ratio of serum total to high-density lipoprotein cholesterol, and those with beta carotene intake greater than the median level.
This study provides evidence of protection against early AMD through:
- regular consumption of fish and nuts
- greater consumption of omega-3 polyunsaturated fatty acids
- low intakes of foods rich in linoleic acid
SOURCE: Dietary Fatty Acids and the 10-Year Incidence of Age-Related Macular Degeneration, The Blue Mountains Eye Study, Tan, et al, Arch Ophthalmol. 2009;127(5):656-665.
For more related research studies, click here for Natural Eye Care Related research on nutrition and macular degeneration.