Mediterranean diet is the common term for dietary practices traditionally found in the regions along the rim of the Mediterranean Sea, which sits between Europe and Africa. Over the years, numerous individual research teams have concluded that adherence to this type of diet lowers the risks for dementia, a mental health condition characterized by a steep decline in memory and/or certain other everyday mental functions. In a new, broad-scale study review published in July 2013 in the journal Epidemiology, a team of British researchers analyzed 12 previous studies on this issue. These researchers concluded that a Mediterranean diet provides some protection against dementia, but does not necessarily provide protection against all forms of dementia, or against relatively small declines in normal brain function.
The study was led by researcher Iliana Lourida. She said: “Mediterranean food is both delicious and nutritious, and our systematic review shows it may help to protect the ageing brain by reducing the risk of dementia. While the link between adherence to a Mediterranean diet and dementia risk is not new, ours is the first study to systematically analyse all existing evidence.”
Mediterranean Diet Basics
The traditional Mediterranean diet is based on the daily consumption of large amounts of a variety of vegetables and fruits, unprocessed or minimally processed grains, nuts and beans (which belong to a family of plants called legumes). Instead of butter, adherents to the diet typically consume olive oil or other oils that contain relatively healthy fats known as unsaturated fats. Poultry and fish usually replace the red meats found in American diets, and herbs and spices frequently function as healthier replacements for table salt and other forms of sodium. Many adherents of Mediterranean diets also consume moderate amounts of red wine (defined as a maximum of two glasses per day for men and a maximum of one glass per day for women).
Dementia is the common name for a type of brain cell damage that can produce such effects as a decline in memory skills, a reduced ability to think logically or make appropriate judgments, a reduced ability to use words properly or understand the words spoken by others, diminished awareness of one’s surroundings and declining vision-related health. Conditions capable of producing one or more of these symptoms of brain dysfunction include Alzheimer’s disease, vascular dementia, frontotemporal dementia, Parkinson’s disease, dementia with Lewy bodies, Huntington’s disease and various forms of traumatic brain injury. In mental health terms, the American Psychiatric Association classifies the effects of each of these conditions as either a relatively moderate ailment called mild neurocognitive disorder or a more severe ailment called major neurocognitive disorder.
In the study review published in Epidemiology, researchers from the University of Exeter School of Medicine analyzed the findings of 12 previous studies that looked at the potential effects of a Mediterranean diet on dementia risks and general brain function. They performed this review because, while each prior study had come to its independent conclusion on the issue, no researchers had taken a larger perspective and examined the entire body of research on a Mediterranean diet’s brain-related effects. Eleven of the 12 studies analyzed during the review were observational studies, which means that the people conducting them did not actively intervene in the lives of the study participants. The remaining study was a controlled study; this means that the researchers did directly intervene in the study participants’ lives in a consistent, scientifically systematic way. As a rule, controlled studies provide a higher degree of scientific proof than observational studies.
After completing their analysis, the University of Exeter researchers concluded that regular consumption of a Mediterranean diet does indeed appear to reduce the risks for Alzheimer’s-related dementia, in particular. This is potentially an important finding, since most people affected by dementia have Alzheimer’s disease. In addition, the researchers concluded that people who regularly consume a Mediterranean diet generally have good long-term brain function, and also have generally smaller chances of experiencing a decline in brain function than people who eat a traditional American diet. However, the authors of the review did not find that a Mediterranean diet reduces the risks for vascular dementia, which is the second most common source of dementia in the U.S. In addition, despite larger statistical trends, the authors could not conclusively determine whether habitual intake of a Mediterranean diet actually reduces any given person’s risks for developing a form of minor brain dysfunction called mild cognitive impairment.
The authors of the review in Epidemiology emphasize the fact that they found many inconsistencies between the conclusions made by the researchers carrying out each of the 12 studies under consideration. They also emphasize the fact that almost all of the previous studies were observational studies, and therefore provide a lower level of scientific verification than controlled studies would provide. For these reasons, the authors point toward a need for more, higher-quality research on this important mental health issue.