by Dan Roberts
May 20, 2007
(Updated April 15, 2008)
Recent studies have shown that omega-3 fatty acids and fish consumption may reduce the risks of age-related macular degeneration (AMD), Alzheimer’s disease, inflammation and depression.
The Age-Related Eye Disease Study (AREDS) Research Group showed that dietary total docosahexaenic acid (DHA), an omega-3 fatty acid contained in fish oil, is beneficial to people with AMD. The study, published in the May 2007 issue of the Archives of Ophthalmology, further verified what leading nutritionists have been saying for years: that several servings of the right kinds of fish per week are good for the retina.
Fish with the highest amount of omega-3 are wild chinook or sockeye salmon, European anchovies, Atlantic/Pacific herring, small Atlantic/Pacific mackerel, black and red caviar, shrimp and Pacific sardines. Omega-3 can also be obtained from freshly-ground flaxseed or in stable, mercury-free fish oil supplements. Up to 200 mg of supplementary DHA is recommended for people who do not get enough fish in their diet.
Another study published in the April 18, 2007 issue of The Journal of Neuroscience, suggests that DHA may help prevent the accumulation of tau, a protein thought to be associated with brain lesions in Alzheimer’s disease.
Researchers from the University of California Irvine fed genetically modified mice different ratios of omega-3 fatty acids, DHA and omega-6 linoleic acid. Omega-6, which initiates the body’s beneficial inflammation response to disease or injury, is already plentiful in a normal diet, and too much of it can lead to uncontrolled inflammation–thought to be a major cause of AMD.
Mice that were fed a higher amount of omega-3 and DHA than omega-6, and mice that were fed only DHA, had lower levels of tau and a peptide called beta-amyloid (a constituent of amyloid plaques in the brains of Alzheimer’s patients). The study also showed that DHA works better alone than in combination with omega-6 fatty acids.
Some types of fish contain high amounts of omega-6 and should, therefore, be avoided. Fish that contain dangerously high amounts are grouper, halibut, pompano, catfish, and Atlantic salmon.
Omega-3 also seems to help lower levels of depression. A report in the journal Psychosomatic Medicine by researchers at Ohio State University in Columbus found that people who consumed much more omega-6 than omega-3 fatty acids reported more symptoms of depression.
All of these findings give further support to the current AREDS2 research, which is looking at adding omega-3 fatty acid DHA to the original formula. Meanwhile, strong evidence suggests that it should be an integral part of everyone’s diet, either through food or through supplementation.
A word of caution: high doses of omega-3 have a blood thinning effect. A study published in the New England Journal of Medicine (1986 April 10; 314(15): 937-42), showed that 10 grams of EPA (eicosapentaenoic acid, one of the active ingredients in fish oil) have the same anti-coagulant effect as a single aspirin dose of 320 mg. If you are already on blood thinners, you should talk to your doctor about supplementing with high quantities of fish oil.
(Some nutritional information in this article was provided by Ellen Troyer, MT, MA, Executive Vice President & Chief Research Officer, Biosyntrx.com.)
UPDATE: APRIL 15, 2008
The benefits of omega-3 (EPA and DHA) fatty acid dietary supplements for maintaining vision are well-known, and more positive effects in related areas continue to be found. One recent discovery is that omega-3 may help with symptoms of depression, and another study links prenatal omega-3 to increased visual acuity and cognitive development in babies.
A double blind study published in the Australian and New Zealand Journal of Psychiatry compared omega-3 to fluoxetine (eg. Prozac) and a combination of the two. Sixty participants were given either 1000 mg EPA, 20 mg fluoxetine, or a combination for 8 weeks. Patients were analyzed every 2 weeks, and 48 patients who completed at least 4 weeks of the study were included in the results. Using the Hamilton Depression Rating Scale (HDRS), researchers found a decrease in baseline 50% in the fluoxetine, 56% in the EPA group and 81% in the combination group. EPA and fluoxetine combination, therefore, was concluded to be superior to either of the two alone.
Another study, published in the Journal of Pediatrics, has reported that omega-3 supplementation in the last months of pregnancy may increase cognitive and motor skills in infants. U.S. and Canadian researchers tested 109 babies at six and 11 months of age, finding that their visual acuity and cognitive and motor development were closely linked to the level of DHA in umbilical cord blood at birth.
These findings further confirm the value of omega-3 in our diet.
UPDATE: MARCH 2009
What if you don’t like fish? A study in England reported that nearly as much benefit can be gained from plant foods containing alpha-liolenic acid. Blood tests showed that women who avoided fish actually became more efficient at converting alpha-liolenic acid into omega-3. Study subjects who avoided fish altogether actually showed blood levels of omega-3 only about 10 percent lower than those who ate fish. Best sources of alpha-liolenic acid are walnuts, flaxseed, tofu, and canola and soybean oils. (Source: Reader’s Digest, Feb 2009, p. 70.)