The Mediterranean diet has been the subject of a recent systematic review that aims to see if its lifestyle approach shows links with lower rates of Alzheimer’s, dementia, and other signs of age-related cognitive decline. Overall, the findings are supportive of the diet, though it has some minor yet unavoidable issues.
The Mediterranean diet (MD) is an approach that emphasizes high consumption of fruits, vegetables, legumes, olive oil, and unrefined cereals. It uses moderate intake of dairy products and alcohol and also uses a limited consumption of meat. Given that this makes for a balanced and well-rounded diet, it has been associated with a number of benefits, particularly in relation to chronic conditions like heart disease or diabetes.
For this analysis, the researchers looked at 32 different studies. Five were randomly controlled trials and 27 were observational studies. The findings are below:
- Three studies found no correlation between MD and Alzheimer’s
- Three found no correlation between MD and cognitive impairments
- Five found no association between MD and cognitive function
- The rest showed associations between MD and improved cognitive function, decreased risk of dementia, decreased risk of cognitive impairment, or decreased risk of Alzheimer’s. The number of studies in these subcategories was not mentioned
Basically, there were 11 studies finding no associations and 21 studies that found an association between the Mediterranean diet and some form of cognitive improvement or protection. This suggests that following the Mediterranean diet is associated with better cognitive performance and reduction in cognitive decline (age-related or otherwise). A few things to keep in mind, however:
- There was high heterogeneity between studies, meaning there were significant differences in how each was conducted. This makes comparisons tricky (not impossible, just harder)
- Most of the studies were observational, meaning that by definition they cannot prove cause-and-effect, only show correlation
- It is unclear whether the observed results were from the diet as a whole or specific elements within it
Most of these are the sort of annoying-but-unavoidable issues that come up when trying to conduct systematic reviews like this. A review can only be as good as the studies it examines, and the majority of these findings suggest the Mediterranean diet does have some connection to reduced Alzheimer’s, dementia, and cognitive decline risk. The “how” and “why”, as well as validation and verification, will need to be left to others.
Petersson, S., and Philippou, E., “Mediterranean Diet, Cognitive Function, and Dementia: A Systematic Review of the Evidence,” Advances in Nutrition, 2016; 10.3945/an.116.012138.