In addition to reducing the risk of cardiovascular disease and cancer, following the Mediterranean diet can preserve memory and protect against cognitive impairment, a new study published in Neurology shows.

Also associated with longer survival and reduced mortality, the Mediterranean diet is high in plant products, olive oil, and omega-3 fatty acid. Conversely, the diet is low in saturated fats, such as those found in red meat and dairy products.

The study showed that people who adhered to the Mediterranean diet were 13 percent less likely to experience cognitive impairment than those who did not follow the diet closely. Among non-diabetic participants, diet followers benefitted even more, with 19 percent lower odds of cognitive decline.

Led by Dr. Georgios Tsivgoulis of University of Alabama at Birmingham and the University of Athens, Greece, the study was the largest to link the diet and memory, with a sample of 17,000 people averaging 64 years of age. The majority of participants hailed from an 11-state region of the south infamously known as "the Stroke Belt," which has the highest stroke mortality rates in the U.S. Stroke is one of many known risk factors for dementia.

People who had a history of stroke or cognitive impairment from the beginning were excluded from the study. Eligible participants were followed over the course of four years: 47 percent had high adherence to the Mediterranean diet, 53 percent had low adherence.

Their cognitive ability was periodically assessed by researchers using a Six-Item Screener, a short questionnaire that measures a person's ability to recall the date and simple words after a brief distraction.

Seven percent of participants experienced incident cognitive impairment, which was defined as a downward shift from intact cognitive status to a score of less than 4 out of 6 on a follow-up test. In contrast, only 1 percent of the participants experienced a stroke, a major impetus for cognitive impairment.

The 13 percent lower-risk for cognitive impairment in Mediterranean diet adherents persisted after adjusting for demographic variables and environmental factors. However, participants diagnosed with diabetes (17 percent of total participants) did not  benefit cognitively from following the diet.

The connection between diabetes and incident cognitive impairment is unknown, but could result from an increased production and less clearance of amyloid, a protein that is the culprit in Alzheimer's dementia and other disorders.

While researchers looked at the relationship between diet and cognitive impairment only, rather than dementia, the study nonetheless suggests that the Mediterranean diet might prevent the disorder. With 17 percent of adults over 70 years old with some form of dementia and few known cures, researchers have focused on ways to prevent cognitive decline.

"Diet is an important modifiable activity that could help in preserving cognitive functioning in late life," said Dr. Tsivgoulis.