Fish consumption improved brain volume in the frontal lobes, temporal lobes (including the hippocampus) and posterior cingulate gyrus, as shown on high-resolution, three-dimensional volumetric magnetic resonance imaging (MRI). "That’s important because these are areas of the brain that are responsible for memory and learning and are severely affected by Alzheimer’s disease," reported Dr. Cyrus A. Raji of the University of Pittsburgh.

Raji and his colleagues analyzed data collected at three time points from the ongoing Cardiovascular Health Study-Cognition Study. In 1989-1990, 260 subjects (mean age 71 years) completed standardized diet questionnaires. In 1998-1999, these individuals (mean age 78 years) underwent volumetric MRI.

An analysis of clinical conversion to mild cognitive impairment (MCI) or Alzheimer’s disease (AD) in 2002 among study participants (mean age 82 years) found that individuals with larger brain volumes as a result of weekly baked or broiled fish consumption had a greatly reduced incidence of MCI or AD, compared with individuals who did not eat fish regularly.

Clinical conversion rates to MCI or AD were 30.8% for non–fish eaters, compared with 8% for individuals whose brains benefited partially from fish consumption (as shown on volumetric MRI), and 3.2% for individuals whose brains benefited fully from fish consumption.

These findings indicate "a large reduction in the risk for developing AD or MCI as a result of consuming baked or broiled fish," Raji said

The benefits of regular fish intake persisted even after accounting for such potential confounding variables as age, gender, head size, and cerebrovascular disease.

Study participants who were not fish eaters and who showed atrophy in the hippocampus -- the region most frequently affected by AD -- had a 47% incidence of MCI or AD, compared with only 28% of fish eaters with larger hippocampal volumes, he reported.

In addition, mean scores on cognitive tests of working memory were significantly higher (P less than .05) in individuals who ate fish weekly compared with those who did not. The improvement remained even after accounting for potential confounders such as age, gender, and education.

The researchers also looked at cognitive test scores and brain volumes and found a relationship between larger frontal lobe volumes in fish eaters and higher working memory test scores. "This makes a lot of sense, because the frontal lobes are responsible for working memory function," Raji said.

The reduced risk of MCI and AD among fish eaters in this study probably stems from the protective benefits of omega-3 fatty acids, he noted. Omega-3 fatty acids are believed to increase blood flow to the brain, act as antioxidants and anti-inflammatories, and prevent the accumulation of the amyloid plaques characteristic of AD. Consumption of fried fish, which is high in cholesterol and low in omega-3 fatty acids, did not confer any benefits.

Data presented by Raji at last year’s meeting of the Radiological Society of North America (Internal Medicine News, Dec. 20, 2010) showed the protective benefits of physical activity in preserving brain volume and reducing the risk of AD and MCI in the same cohort. "What we’re adding to the picture this year is specific information on diet," he said. "The long-term goal of this research is to incorporate our understanding of all the various lifestyle factors that could reduce risk and give us a unified picture of how to best prevent the disease."

 From the December 5, 2011, Prepared Foods' Daily News.