Eating fish has long been linked with heart health. Now new research adds to growing evidence that fish is good for the brain as well.
Researchers at the University of Pittsburgh found that people who ate baked or broiled fish just once a week had a lower risk of developing Alzheimer’s disease. They were also at lower risk of mild cognitive impairment, a type of memory loss that sometimes leads to Alzheimer’s.
The fish eaters had more brain gray matter, as measured by M.R.I., or magnetic resonance imaging, brain scans, than those who didn’t regularly eat fish. Greater brain volume may indicate intact memory and thinking functions, whereas brain shrinkage has been linked to Alzheimer’s disease and other forms of dementia.
Fried fish, unlike the baked or broiled kind, did not provide brain-protective benefits. The findings were presented at the annual meeting of the Radiological Society of North America.
"This is the first study to establish a direct relationship between fish consumption, brain structure and Alzheimer's risk," said Dr. Cyrus Raji of the University of Pittsburgh. "The results showed that people who consumed baked or broiled fish at least one time per week had better preservation of gray matter volume on M.R.I. in brain areas at risk for Alzheimer's disease."
The study looked at 260 men and women who were part of the long-running Cardiovascular Health Study. None had Alzheimer’s or serious memory problems at the start of the study. They were given questionnaires about what they ate; 163 reported eating fish at least once a week. Most had fish one to four times weekly.
Using specialized M.R.I. brain scanning, the researchers then measured brain volume of each of the study participants, including 3-D measurements of brain gray matter. Over a 5- to 10-year period, the regular fish eaters had greater preservation of brain gray in areas like the hippocampus that are critical for memory.
Compared to those who didn’t eat baked or broiled fish regularly, the fish eaters had an almost five-fold reduction in the risk of Alzheimer’s or mild cognitive impairments, the researchers found. The brain protective effects of fish appeared to be independent of other Alzheimer’s risk factors like age, years of schooling, obesity, level of physical activity, or the presence of APOE-E4, a gene that predisposes to Alzheimer’s.
"Consuming baked or broiled fish promotes stronger neurons in the brain's gray matter by making them larger and healthier," Dr. Raji said. "This simple lifestyle choice increases the brain's resistance to Alzheimer's disease and lowers risk for the disorder."
People who ate fish also did better on tests of thinking skills, including working memory, which allows people to focus on tasks and commit information to short-term memory. "Working memory is destroyed by Alzheimer's disease,” Dr. Raji said. “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."
Other studies have found brain benefits from eating fish, including a large study conducted in developing countries that found that a diet rich in fish may lower the risk of Alzheimer’s disease. The more fish people ate, the less likely they were to develop the serious memory loss of dementia. Studies of people living in Italy, France and Spain who eat a traditional Mediterranean diet rich in fish as well as fruits and vegetables have likewise shown that the diet may have brain-protective effects.
In addition to a possible protective effect, dietary consumption of fish might also reduce the intake of less healthy food by acting as a substitution. In other words, a serving of fish might substitute for a cut of red meat high in saturated fat.
Fish oil supplements, a popular remedy for heart health, have also been shown to benefit the brain. Fish oils contain omega-3 fatty acids like DHA, or docosahexaenoic acid. Higher levels of DHA in the brain might be linked to a lower risk of developing Alzheimer's disease. Researchers speculate that the omega-3s in fish oil may quell inflammation, which is emerging as a possible underlying cause of heart disease and Alzheimer’s.
By ALZinfo.org, The Alzheimer's Information Site. Reviewed by William J. Netzer, Ph.D., Fisher Center for Alzheimer's Research at The Rockefeller University.
Source: Kirk Erickson, Ph.D., Oscar Lopez, M.D., Lewis Kuller, M.D., et al: Radiological Society of North America.