Nutritionists have long endorsed fish as part of a heart-healthy diet, and now some studies suggest that omega-3 fatty acids found in the oil of certain fish may also benefit the brain by lowering the risk of Alzheimer’s disease. In order to test whether an omega-3 fatty acid can impact the progression of Alzheimer’s disease, researchers supported by the National Institute on Aging (NIA), part of the National Institutes of Health, will evaluate one in a clinical trial, the gold standard for medical research.

The study will be conducted nationwide by the Alzheimer’s Disease Cooperative Study (ADCS), a consortium of leading researchers supported by NIA and coordinated by the University of California, San Diego. The trial will take place at 51 sites across the United States and seeks 400 participants age 50 and older who have mild to moderate Alzheimer’s disease. Joseph Quinn, M.D., associate professor of neurology at Oregon Health and Science University, is directing the study.

Researchers will be evaluating primarily whether the omega-3 fatty acid DHA (docosahexaenoic acid), taken over many months, slows the progression of both cognitive and functional decline in people with mild to moderate Alzheimer’s. During the 18-month clinical trial, investigators will measure the progress of the disease using standard tests for functional and cognitive change.

“The evidence to date in observational and animal studies on omega-3 fatty acids and Alzheimer’s disease warrants further evaluation in a rigorous clinical trial,” says NIA Director Richard J. Hodes, M.D. “This study is one of a number we are undertaking in the next few years through the ADCS to test compounds that might play a role in preventing or delaying the symptoms of this devastating disease.”

“By participating in this study, volunteers will make an invaluable contribution to Alzheimer’s disease research progress,” says Quinn, the study’s principal investigator. “We are indebted to those who graciously volunteer to participate in clinical studies.”

The trial will use DHA donated by Martek Biosciences Corporation of Columbia, Md. Participants will receive either two grams of DHA per day or an inactive placebo pill. About 60 percent of participants will receive DHA, and 40 percent will get the placebo. Doctors and nurses at the 51 research clinic sites will monitor the participants in regular visits throughout the trial. To ensure unbiased results, neither the researchers conducting the trial nor the participants will know who is getting DHA and who is getting the placebo.

In addition to monitoring disease progression through cognitive tests, researchers will also evaluate whether taking DHA supplements has a positive effect on physical and biological markers of Alzheimer’s, such as brain atrophy and proteins in blood and spinal fluid.