Eating Fish Reduces Risk of "Silent" Brain Damage by 26%

LAST NIGHT'S BROILED TUNA STEAK may already be hard at work protecting your brain. A new study of data from four US communities finds that older adults who ate tuna and similar fish at least three times a week were less prone to a subtle form of brain damage linked to dementia and stroke. But the protective benefit was seen only from baked or broiled fish — not fried fish such as fish sticks.

Researchers used data on 3,660 participants in the Cardiovascular Health Study, age 65 or older, who underwent at least one MRI scan; 2,313 had two scans five years apart. All completed food-frequency questionnaires.

Published in Neurology, the study focused on "silent brain infarcts" — small areas of tissue that die from an insufficient supply of blood. Such damage is called "silent" or "subclinical" because patients show no obvious symptoms, and the infarct can be detected only by a brain scan such as an MRI. Silent brain infarcts are associated with future stroke risk as well as cognitive and neurobehavioral impairment.

"Previous findings have shown that fish and fish oil can help prevent stroke, but this is one of the only studies that looks at fish's effect on silent brain infarcts in healthy, older people," said lead author Jyrki K. Virtanen, PhD, of 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."

Virtanen and colleagues found that subjects who ate the most tuna and other non-fried fish had a 26% reduced risk of silent infarct compared to those eating the least, less than one serving a month. For each additional weekly serving of tuna or other baked/broiled fish, the risk of infarct fell by 7%. Those eating at least three servings of fish per week also scored 10.6% better on a test of white matter in the brain.

No protective benefit was seen from fried fish like fish sticks, typically made from varieties such as cod or pollock that are low in omega-3 fatty acids. When researchers estimated intake of the two most important omega-3s found in oily fish — EPA and DHA — they found an association between higher intake and reduced risk of silent brain infarct.

Noting that omega-3 consumption has previously been linked to lower risk of dementia and Alzheimer's, Virtanen and colleagues added, "Our findings suggest that prevention of subclinical infarcts and white-matter anomalies may be one mechanism whereby fish or [omega-3 fatty acid] consumption may decrease the development of these debilitating conditions."

TO LEARN MORE: Neurology, Aug. 5, 2008; abstract at .

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