The traditional Mediterranean diet is characterised by large intakes of whole grains, plant foods and red wine, as well as oily fish and lean meats. It addition the diet contains low levels of red and processed meat, and refined foods, particularly sugar. Research has shown that adherence to the diet is beneficial to a number of conditions including obesity, type 2 diabetes, cardiovascular disease and cancer. The benefits of the Mediterranean diet may stem from the high concentrations of plant antioxidants contained within the olives, green leafy vegetables and fruits, that may decrease oxidative stress. In addition the diet contains high concentrations of omega-3 oils from fish, and this may improve the balance of eicosanoid formation within the body, favouring production of the anti-inflammatory series 1 and 3 prostaglandins at the expense of the series 2 prostaglandins, and series 4 leukotrienes.
Therefore, the Mediterranean diet may be effective at controlling conditions characterised by inflammation and oxidative stress. One conditions that this may apply to is cognitive decline in ageing subjects. For example, researchers1 have analysed the adherence of elderly subjects (≥60 years) to the Mediterranean diet or the 2005 Health Eating Index (HEI), while cognitive function was assessed in subjects at 3 year intervals using a composite measure of global cognition. The mean diet score for the Mediterranean diet was 28.2 and the mean score for the HEI was 61.2, indicating subjects dietary patterns more closely followed the HEI guidelines. Higher scores on the Mediterranean diet were associated with a slower cognitive decline in subjects (following adjustment for know risk factors such as age, education levels, sex, race and participation in mental activities). However, there was no association between the HEI and the rate of cognitive decline.
This study provides evidence that the adherence to the Mediterranean diet is beneficial to mental health, supporting previous data that shows a reduced risk of Alzheimer’s disease and mild cognitive impairment in those who follow the diet. An interesting component of this study was the inclusion of the HEI to allow comparison between the two diets. While there are some common features between the HEI and the Mediterranean diet, such as an emphasis on whole unrefined grains, the HEI is based on the traditional food pyramid. For example, there are no separate categories for alcohol, fish, nuts, legumes, beans or poultry in the HEI. Alcohol is particularly important as there is strong evidence that red wine is beneficial to effects against neuropathology, possibly due to the presence of the polyphenol, resveratrol. Resveratrol may reduce amyloid β production and promote its clearance.
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