Fish really is brain food after all, according to a new study, which shows eating fish can slow the mental decline associated with aging.

The results show that eating fish at least once a week slowed the rate of mental or cognitive decline in elderly people by 10 percent-13 percent per year.

“That rate of reduction is equivalent to being three to four years younger in age,” write researcher Martha Clare Morris, ScD, of Rush University Medical Center, Chicago, and colleagues in the Archives of Neurology.

Their findings were released online today in advance of the scheduled December publication date in the journal.

Researchers attribute the protective effects of fish on the brain to omega-3 fatty acids. Fish, especially oily types like salmon and tuna, are a rich source of omega-3 fatty acids, which are essential for brain development and normal brain functioning.

Eating fish regularly has already been linked to a lower risk of dementia and stroke, and some animal studies show that at least one type of omega-3 fatty acid known as DHA (docosahexaenoic acid) plays an important role in memory performance during aging.

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Fish Slows Mental Decline

In the study, researchers looked at the relationship between fish consumption and age-related cognitive decline in more than 4,000 participants aged 65 and over in the ongoing Chicago Health and Aging Project.

Researchers interviewed the participants every three years and assessed their mental function as well as their diets.

After more than six years of follow up, researchers found that the more fish people ate, the slower their rate of mental decline.

People who ate fish at least once a week experienced a 10 percent-13 percent lower rate of cognitive decline than those who ate fish less frequently.

Researchers say these protective benefits of fish persisted even after adjusting for other dietary factors, such as fruit and vegetable consumption.

"This study suggests that eating one or more fish meals per week may protect against cognitive decline associated with older age," write the researchers. "More precise studies of the different dietary constituents of fish should help to understand the nature of the association."

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By Jennifer Warner, reviewed by Louise Chang, MD

SOURCES: Morris, M. Archives of Neurology, Oct. 10, 2005 online edition; vol 62. News release, American Medical Association.