May 2, 2012 -- Early research suggests that eating fatty fish, nuts, and other foods rich in omega-3 fatty acids may help protect against Alzheimer's disease.
In a newly published study, researchers showed that people whose diets contained the most omega-3 had the lowest blood levels of a protein known as beta-amyloid.
Beta-amyloid deposits are commonly found at autopsy in the brains of people with Alzheimer's disease. Several studies also suggest that high blood levels of the protein may predict Alzheimer's disease before memory loss occurs.
Amyloid, Alzheimer's, and Omega-3
In the new study, older people with no evidence of age-related memory loss were questioned about the foods they ate to determine their intake of key nutrients like vitamins B12, C, D, and E, beta-carotene, and various fatty acids.
Blood tests conducted an average of a year after the dietary survey revealed that people who ate the most omega-3 fatty acids had lower beta-amyloid levels. The association was not seen with other nutrients.
Even a small increase in omega-3 fatty acids over the daily average was associated with meaningfully lower beta-amyloid levels, says researcher Nikolaos Scarmeas, MD, of New York's Columbia University Medical Center.
There are two major types of dietary omega-3 fatty acids: alpha-linolenic acid (ALA), abundant in soybean oil, canola oil, walnuts, and flaxseed; and docosahexaenoic acid (DHA), found in salmon, sardines, tuna, and other fatty fish.
"This adds to the evidence that diet may play a role in [memory] decline," Scarmeas tells WebMD. "We know that omega-3 helps protect against heart disease. Now there is emerging evidence that it may protect the brain as well as the heart."
Mediterranean Diet and Brain Health
The study was published in the journal Neurology.
Earlier research by Scarmeas and colleagues also suggested a link between the omega-3-rich Mediterranean diet and protection against Alzheimer's disease.
The Mediterranean diet includes plenty of fruits, vegetables, nuts, and fatty fish, but is low in red meat, processed meats, butter, and other high-fat dairy products.
In a 2010 study involving more than 2,000 older people with no evidence of memory decline, the researchers found that those whose diets most closely followed the Mediterranean model were least likely to develop Alzheimer's disease over four years of follow-up.
A recent brain imaging study also suggests a role for omega-3 in protecting aging brains.
Funded, in part, by the National Institute on Aging, the study found that older people without dementia whose diets were low in omega-3 had the smallest brains.
Decreased brain volume is a sign of brain aging.
Although there are plenty of good reasons to include omega-3-rich foods in your diet, Barbara Cornblatt, PhD, says it is too soon to recommend eating these foods or taking omega-3 supplements just to lower Alzheimer's risk.
An investigator with the Feinstein Institute for Medical Research in Manhasset, N.Y., Cornblatt is studying whether taking fish oil supplements helps prevent psychiatric disorders in teenagers.
"There is a lot of research examining the impact of omega-3 fatty acids on brain function, but it is all pretty preliminary at this point," she tells WebMD.