Even our grandmothers told us fish was "brain food"--and now scientists have evidence to back the claim.
Researchers with the Department of Veterans Affairs (VA) and the University of California at Los Angeles (UCLA) found that a diet high in docosahexenoic acid, or DHA--an omega-3 fatty acid found in relatively high concentrations in cold-water fish--dramatically slowed the progression of Alzheimer's disease in mice. Specifically, DHA cut the harmful brain plaques that mark the disease. The results appear in the March 23 online edition of the Journal of Neuroscience.
Senior author Greg M. Cole, Ph.D., a neuroscientist at the Greater Los Angeles VA Healthcare System and UCLA, said that unlike many studies with mice, this one points to the benefits of a therapy that is easily available and already touted for other medical conditions. DHA--either from food sources such as fish and soy, or in fish-oil supplements--is recommended by many cardiologists for heart health, based on scores of previous studies.
"The good news from this study is that we can buy the therapy at a supermarket or drug store," said Cole. "DHA has a tremendous safety profile--essentially no side effects--and clinical trial evidence supports giving DHA supplements to people at risk for cardiovascular disease."
The new study involved older mice genetically altered to develop Alzheimer's disease. The researchers fed one group of the mice DHA-fortified chow. The control mice ate a normal or DHA-depleted diet.
After three to five months--the equivalent of several years in human biology--the high-DHA group had 70-percent less buildup of amyloid protein in the brain. This sticky protein makes up the plaques, or patches, that are a hallmark of Alzheimer's.
A similar study by Cole's group published in Neuron last fall showed that DHA protected against damage to the "synaptic" areas where brain cells communicate and enabled mice to perform better on memory tests.
The studies, say the scientists, suggest that even people who are genetically predisposed to the disease may be able to delay it by boosting their DHA intake.
Omega-3 fatty acids, typically deficient in the American diet, are essential for human health. DHA in particular is vital to proper brain function, as well as eye health and other body processes. In recent years epidemiologists have tied fish-rich diets to a lower incidence of Alzheimer's disease and homed in on DHA as the preventive factor. Omega-3 fatty acid supplements are now being tested in clinical trials with early-stage Alzheimer's patients in the United States, Canada and Sweden to see if the therapy really slows the disease.
Food sources of omega-3 fatty acids include fish such as salmon, halibut, mackerel and sardines, as well as almonds, walnuts, soy, and DHA-enriched eggs. Concerns about mercury contamination in fish have helped popularize purified DHA supplements based on fish oil or algae. Last year, Cole's team identified another nutrient that appears to combat Alzheimer's plaques in mice: curcumin, the yellow pigment in turmeric, one of the spices that make up curry powder. Researchers became interested in curcumin's potential to prevent or treat Alzheimer's disease after noting the low prevalence of dementia among the elderly in India, where curry is a staple.