New Support for Fish in the Fight Against Alzheimer's Study links fishy diet to reduced risk of cognitive decline.

Nov. 30, 2011 -- A new study suggests eating baked or broiled fish may help fight the brain shrinkage and cognitive decline associated with Alzheimer's disease.

Researchers from University of Pittsburgh Medical Center tracked fish consumption and measured brain volume and memory function in 260 cognitively normal adults over 10 years. In the end, study participants who ate more fish had bigger brain areas -- particularly the hippocampus, which is known to shrink in Alzheimer's -- and better memory than their fish-declining counterparts.

"We found higher levels of working memory in people who ate baked or broiled fish on a weekly basis, even when accounting for other factors, such as education, age, gender and physical activity," Dr. Cyrus Raji, lead author of the study, said in a statement. Raji presented his findings today at the annual meeting of the Radiological Society of North America.

Other research has hinted at fish's brain-boosting effects. A 2010 study published in Archives of Neurology found that people who ate a Mediterranean diet high in fish, fruits and veggies were 38 percent less likely to develop Alzheimer's disease over the next four years.

"Certainly this is not the first article to show a beneficial connection between fish consumption and Alzheimer's disease risk," said William Thies, chief medical and scientific officer of the Alzheimer's Association. "It seems to fit with what we know about eating fish."

This is the first time, however, that brain imaging has been used to support the findings.

Raji and colleagues used magnetic resonance imaging to capture 3-D images of subjects' brains at the beginning and end of the 10-year study. Those who ate more fish tended to have bigger brain areas implicated in Alzheimer's, including the hippocampus, the posterior cingulate and the orbital frontal cortex.

While the results are encouraging, they do not necessarily mean eating fish protects against Alzheimer's -- an incurable disease that affects as many as 5.1 million Americans. Rather, they provide support for a "possible beneficial effect of a diet rich in fish ingredients," according to Zaven S. Khachaturian, president of the Campaign to Prevent Alzheimer's Disease by 2020.

The study suggests an association, not causation. It could be, rather, that another behavior related to fish consumption is exerting the positive effect. The association only held up for baked or broiled fish, not fish that was fried, suggesting that other lifestyle factors may be at play. Only large, properly controlled clinical trials can determine whether eating fish truly fights cognitive decline, said Khachaturian.

One such trial of docosahexaenoic acid, an omega-3 fatty acid found in fish and fish oil supplements, found no benefit in slowing Alzheimer's disease, according to a 2010 study published in the Journal of the American Medical Association. But the study authors said there was still a possibility that DHA supplementation early on -- before Alzheimer's-related brain shinkage and memory loss starts -- might be protective.

"Individuals intermediate between healthy aging and dementia, such as those with mild cognitive impairment, might derive benefit from DHA supplementation, although further study will be necessary to test this hypothesis," they wrote.