September 16, 2008
Eating tuna and other types of fish may help lower the risk of memory decline and stroke in healthy older adults, a new study reports. Fish that was baked or broiled, but not fried, appeared to have benefits for the brain.
The findings are consistent with earlier reports that suggest that eating oily fish like tuna, salmon, mackerel, sardines and anchovies may help to keep the mind and memory sharp. Eating fish may also help to ease the agitation and depression of Alzheimer's, research shows. [See the article, "Fish Oil May Ease Agitation and Depression of Alzheimer's"]
Fish oils contain omega-3 fatty acids like EPA and DHA, which are known to be good for cardiovascular health. They also may help protect the brain against strokes and memory loss. DHA, or docosahexaenoic acid, and EPA, or eicosapentaenoic acid, are both thought to have disease-fighting properties. Researchers speculate that the DHA and EPA in omega-3s may quell inflammation, which is emerging as a possible underlying cause of heart disease and other ills, including Alzheimer's disease.
The current study, published in Neurology, the medical journal of the American Academy of Neurology, followed 3,660 seniors aged 65 and older as part of the Cardiovascular Health Study. Participants were given extensive food questionnaires that asked about eating fish and other foods. All the participants also underwent M.R.I. brain scans, which looked for small regions of dead tissue, or infarcts, in the brain. Infarcts are linked to areas of poor blood flow in the brain and are a marker for strokes, poor thinking skills and dementia.
Brain scans were performed again five years later on 2,313 of the participants, along with questionnaires about fish in their diets. The study found that people who ate broiled or baked tuna and other fish high in omega-3 fatty acids three times or more per week had a nearly 26 percent lower risk of having brain infarcts and other damage to the brain. The brain lesions did not produce any overt symptoms, the way a stroke might lead to speech or movement problems. But silent brain infarcts are known to be linked to dementia and may precede a stroke or be related to transient ischemic attacks, a so-called "mini-stroke."
Eating just one serving of broiled or baked fish per week led to a 13 percent lower risk of brain infarcts. Those who ate fried fish, such as fish filets, fish sticks or commercially prepared fried fish dishes, did not show any brain benefits.
"While eating tuna and other types of fish seems to help protect against memory loss and stroke, these results were not found in people who regularly ate fried fish," said lead author Jyrki Virtanen, Ph.D., R.D., with the University of Kuopio in Finland. "More research is needed as to why these types of fish may have protective effects, but the omega-3 fatty acids EPA and DHA would seem to have a major role." It's possible that the kinds of fish that are generally eaten fried might not be those that are rich in omgea-3s. It is not known whether the frying process itself affects the protective ability of the fish, but this is still possible.
"Previous findings have shown that fish and fish oil can help prevent stroke, but this is one of the only studies to look at fish's effect on silent brain infarcts in healthy, older people," said Dr. Virtanen. Research shows that silent brain infarcts, which are only detected by brain scans, are found in about 20 percent of otherwise healthy elderly people.
More research is needed to help determine whether fish or fish oil supplements really help keep the mind sharp. In the meantime, as more and more studies point to the benefits of fish, it may be a wise choice to order your fish baked or broiled -- and hold off on the fried.
J. K. Virtanen, Ph.D., R.D.; D. S. Siscovick, M.D., M.P.H.; W. T. Longstreth, Jr., M.D., M.P.H.; et al: "Fish Consumption and Risk of Subclinical Brain Abnormalities on MRI in Older Adults." Neurology, Volume 71, August 5, 2008, pages 439-446.