A new review concludes that a Mediterranean diet is good for the brain, after finding that people who follow the diet are less likely to experience cognitive decline and develop Alzheimer's disease.
Lead author Roy Hardman, from the Centre for Human Psychopharmacology at Swinburne University of Technology in Melbourne, Australia, and his team publish their findings in the journal Frontiers in Nutrition.
The Mediterranean diet incorporates a high intake of plant-based foods, such as fruits, vegetables, whole grains, legumes, and nuts, while limiting intake of red meat and replacing butter with healthy fats, such as olive oil.
The diet also emphasizes eating fish or poultry at least twice a week and using herbs and spices rather than salt to flavor food.
The Mediterranean diet is considered by many as the best eating plan for a healthy heart, with numerous studies showing it can lower the risk of heart disease by reducing levels of low-density lipoprotein (LDL) - or "bad" - cholesterol.
But increasingly, researchers are finding the benefits of a Mediterranean diet may not be limited to the heart; last year, for example, a study found a Mediterranean diet with additional nuts or olive oil may protect against cognitive decline in seniors.
The new review from Hardman and colleagues supports such findings, revealing that the Mediterranean diet may have significant benefits for cognitive function.
Improvements in memory, attention with a Mediterranean diet
For their review, the researchers identified 135 studies conducted between 2000-2015 that looked at how the Mediterranean diet affects cognitive function long term. A total of 18 studies met their strict criteria and were included for systematic review.
In each of these studies, subjects' adherence to a Mediterranean diet was self-reported through completion of food frequency questionnaires or a food diary.
The cognitive function of participants was assessed through a number of tests, including the mini-mental state examination (MMSE) and the computerized mental performance assessment (COMPASS).
Overall, the review revealed that participants with greater adherence to the Mediterranean diet had less cognitive decline, experienced improvements in cognitive function, or were less likely to develop Alzheimer's disease, compared with those who had lower adherence to the diet.
In relation to memory, participants who closely followed the Mediterranean diet experienced improvements in long-term and working memory, as well as improvements in delayed recognition, executive memory, and visual constructs.
Greater adherence to the Mediterranean diet was also associated with improvements in attention and language, the researchers report.
'Even older adults should switch to a Mediterranean diet'
Overall, the researchers say their review suggests there is "encouraging evidence" that following a Mediterranean diet can improve cognitive function.
Additionally, the results revealed that both younger and older adults experienced cognitive benefits by following a Mediterranean diet.
"I would therefore recommend people to try to adhere or switch to a Mediterranean diet, even at an older age."
While the study did not look at the underlying mechanisms by which the Mediterranean diet benefits cognitive function, Hardman says the diet improves a number of risk factors for cognitive decline.
"These include reducing inflammatory responses, increasing micronutrients, improving vitamin and mineral imbalances, changing lipid profiles by using olive oils as the main source of dietary fats, maintaining weight and potentially reducing obesity, improving polyphenols in the blood, improving cellular energy metabolism and maybe changing the gut microbiota, although this has not been examined to a larger extent yet," he explains.
Given the predicted increase in the aging population, Hardman notes that identifying ways to maintain quality of life and reduce the social and economic burdens of illness in older age is important, and he believes adopting the Mediterranean diet is one such strategy.