The relationship between diet and brain function is garnering increasing attention from scientists, and fish, in particular, is one food that is being studied for its potential health effects. Fish is rich in omega-3 fatty acids, which appear to be important in the development and maintenance of proper nerve function in the central nervous system. Moreover, previous research has suggested that diets rich in fish may be protective against dementia.

Now a new study, published in BMJ (formerly the British Medical Journal) , further supports that theory, finding that older adults who ate fish at least once a week had a significantly lower risk of dementia compared with people who never ate fish.

About the Study

French researchers used data from an existing epidemiolgic study of cognitive and functional effects of aging among older adults. During 1991-1992, researchers visited 1674 people aged 68 and older who did not have dementia and who lived at home in southwestern France. Among other things, the researchers recorded how often the participants consumed fish and seafood. Consumption was classified according to four categories:

  • Daily
  • At least once a week (but not every day)
  • From time to time (but not every week)
  • Never

The researchers followed up with the study participants two, five, and seven years after the initial visit to determine how many of them had developed dementia. They used one of two commonly used tools to diagnose dementia: the “mini-mental state examination” or criteria of the Diagnostic and Statistical Manual of Mental Disorders . A neurologist confirmed the diagnoses.

The researchers then calculated the incidence of dementia within the study group and related it to the participants’ consumption of fish. In doing the statistical analyses, the researchers controlled for other factors that could affect risk of dementia, including age, sex, and education level.

The Findings

After adjusting for age and sex, the researchers found that participants who ate fish at least once per week had a 34% lower risk of being diagnosed with dementia compared with people who never ate fish.

However, when education level was included in the analysis, the analysis showed that the protective effect of eating fish was partially explained by higher education level. (The frequency of fish consumption was higher in people with higher education).

Although these findings are interesting, they do not allow researchers to conclusively state that eating fish prevents dementia. As with many studies, this one has a number of limitations. For example, it is possible that subjects did not accurately recall their actual consumption of fish and seafood or that their dietary patterns significantly changed during the study period. This is a common problem with research questionnaires. In addition, the researchers did not account for family history of early dementia. And finally, the size of the study group was relatively small.

How Does This Affect You?

While researchers continue to investigate the potential protective effects of fish on dementia risk, there are several good reasons to include fish as a regular part of your healthful diet. Fish is a good source of protein and it contains omega-3 fatty acids, which research has shown to be protective against cardiovascular disease. In fact, the American Heart Association recommends eating at least two servings (three ounces each) of fish per week for heart health.

When adding fish to your diet, make sure it replaces sources of unhealthful fats in your diet, such as saturated fatty acids found in fatty red meat and high-fat dairy products. And if buying and cooking fresh fish isn’t convenient for you, you can still reap the benefits by buying frozen fish fillets or canned fish, such as tuna, mackerel, herring, and sardines.

Some people prefer to take fish oil pills instead of eating fish, but less research has been done on the potential health benefits of these pills. And because these pills could have potential side effects, consult your doctor before taking these or any dietary supplement.