What is the Mediterranean diet?
The Mediterranean diet typically involves high intakes of fish, vegetables, fruits, cereals and unsaturated fats (mostly in the form of olive oil), low intakes of dairy products, meat and saturated fats and a regular but moderate alcohol consumption.
Adherence to the Mediterranean diet has been previously associated with lower risks of Alzheimer’s Disease. Recently, Scarmeas and colleagues from Columbia University in N.Y. tested whether this diet could also benefit individuals with Mild Cognitive Impairment (MCI). The term MCI applies to individuals who are in the transitional stage between normal aging and Alzheimer’s Disease (AD).
Scarmeas’ study lasted approximately 5 years and involved:
- 1393 cognitively normal participants, 275 of whom developed MCI during the study
- 482 participants with MCI, 106 of whom developed AD during the study
For the cognitively normal individuals, adhering to the Mediterranean diet was associated with a lower risk for developing MCI. Compared with the one-third who had the lowest scores for Mediterranean diet adherence, the one-third with the highest scores for Mediterranean diet adherence had a 28% lower risk of developing MCI and the one-third in the middle group for Mediterranean diet adherence had a 17% lower risk.
For individuals with MCI, adhering to the Mediterranean diet was associated with a lower risk for the transition between MCI and AD. Compared to the one-third with the lowest scores for Mediterranean diet adherence, the one-third with the highest scores for Mediterranean diet adherence had 48% less risk of developing AD and those in the middle one-third of Mediterranean diet adherence had 45% less risk.
These results did not change when the researchers took into consideration age, sex, ethnicity, education, caloric intake, and genetic factors (such as APOE genotype).
Why is this diet good for the brain?
The Mediterranean diet may improve cholesterol levels, blood sugar levels and blood vessel health overall. It may also reduce inflammation (thanks to high intakes of antioxidants). All of these factors have been associated with mild cognitive impairment and dementia.
The Scarmeas’ study shows an association between MCI risk and the Mediterranean diet. Note that an association between 2 things doesn’t mean that one thing (diet) causes the other (lower MCI). Other possible factors may create the association. For instance it is possible that people who follow the Mediterranean diet also have a higher level of physical activity or have a higher socioeconomic status, both of which could result in better health and lower risk of MCI.
Scarmeas, N., Stern, Y., Mayeux, R., Manly, J. J., Schupf, N., & Luchsinger, J. A. (2009). Mediterranean Diet and Mild Cognitive Impairment. Arch Neurol., 66(2), 216-225.