July 20, 2011 (Paris) -- A diet rich in certain omega-3 fatty acids may lower the risk of developing dementia, researchers report.
In a study of more than 2,000 older women and men followed for nearly five years, the more omega-3-rich oily fish they ate, the lower their risk of developing dementia.
The researchers looked specifically at the omega-3 fatty acids DHA (docosahexaenoic acid) and EPA (eiosapentaenoic acid), found in salmon, sardines, tuna, halibut, and mackerel.
Foods like meat and dairy products that are packed with saturated fatty acids, particularly palmitic acid, on the other hand, were liked to an increased risk of dementia, says researcher Deborah Gustafson, PhD, of the University of Gothenburg's Institute for Neuroscience and Physiology, in Sweden. She is a visiting scientist at State University of New York-Downstate Medical Center in Brooklyn, N.Y.
The study doesn't prove cause and effect, only that there is an association between different types of fatty acids and dementia.
Nevertheless, "it seems pretty clear that if you're picking a diet to prevent Alzheimer's disease with the knowledge we have today, you would pick a diet rich in fish, fruits, and vegetables and low in [saturated] fat," William Thies, PhD, scientific director of the Alzheimer's Association, tells WebMD. He was not involved with the study.
About 5.4 million Americans have Alzheimer's disease, which accounts for 60% to 80% of cases of dementia.
The findings were presented here at the Alzheimer's Association International Conference.
The researchers followed 2,363 women and men aged 65 and older participating in a larger aging study. None had dementia at the start of the study.
All filled out a 61-item questionnaire that asked what foods they ate, how much, and how often. Using nutritional charts, the researchers then estimated intake of fatty acids, including EPA, DHA, palmitic acid, and stearic acid.
Neurological exams were given every 18 months. Over a period of four and one-half years, 406 of the participants were diagnosed with dementia.
Results showed that increasing intakes of EPA and DHA were associated with a 20% to 30% lower risk for dementia. Increasing intakes of palmitic acid was associated with higher dementia risk. There was no link between other types of fatty acids and dementia.
The analysis took into account other risk factors for dementia, including age, sex, race, education, and other medical conditions.
The researchers could not take into account every risk factor for dementia, Thies points out.
While the study was not designed to examine how fatty acids might affect dementia risk, Gustafson says that EPA and DHA may be protective due to their chemical and biological properties. They are building blocks for protective brain cell membranes, for example, and they may calm inflammation that can damage brain cell health.
These findings were presented at a medical conference. They should be considered preliminary as they have not yet undergone the "peer review" process, in which outside experts scrutinize the data prior to publication in a medical journal.