Your mother probably told you that fish is brain food. Apparently, she was right. A new study has found that older people who regularly eat fish reduce the amount of cognitive decline they experience.

The Study

In the study, Martha Clare Morris, an epidemiologist at Rush University Medical Center in Chicago, and her team collected data on 6,158 people age 65 and older who lived on the south side of Chicago and were part of the Chicago Health and Aging Project.

The participants filled out a questionnaire about what they ate, and had their cognitive ability tested every three years during the six year study.

People who ate fish once a week had a 10% slower decline in thinking ability over time than people who consumed fish less than weekly. Those who ate two or more fish meals per week had a 13% slower decline in thinking ability. "The rate reduction is the equivalent of being three to four years younger in age," Morris says.

The DHA Connection

Fish is a source of omega-3 fatty acids, which have been shown to be essential for neurocognitive development and normal brain functioning. In addition, fish consumption has been associated with a lower risk of dementia and stroke. Some recent studies have discovered that one omega-) fatty acid in particular, docosahexaenoic acid (DHA), is important for memory in older animals.

Morris believes that increased levels of DHA may be responsible for the slower decline in thinking ability. In a previous study, Morris found that DHA reduced the risk of developing Alzheimer's disease. "DHA is very important for the communication between neurons and the overall functioning of neurons," she explains.

The Jury Is Still Out

At least one expert thinks this study does not make a conclusive case that DHA-or any other omega-3 fatty acid, for that matter-is the reason that fish consumption appears to slow a decline in thinking ability.

Greg M. Cole, associate director of the Alzheimer's Disease Research Center at the David Geffen School of Medicine at the University of California, Los Angeles, says that although Morris's study "also finds reduced cognitive decline associated with increased fish intake, it doesn't find much evidence to relate this to greater omega-3 fatty acid intake.

"One problem is that the questionnaires on fish intake were not that highly correlated with actual blood levels of omega-3," Cole says. "These new results suggest that the jury is still out on whether it is the oil in the fish, specifically the omega-3 fatty acids, that we should try to increase."

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