The Mediterranean Diet
The Mediterranean diet is a modern nutritional recommendation originally inspired by the dietary patterns of Greece, Southern Italy, and Spain in the 1940s and 1950s. The principal aspects of this diet include proportionally high consumption of olive oil, legumes, unrefined cereals, fruits, and vegetables, moderate to high consumption of fish, moderate consumption of dairy products (mostly as cheese and yogurt), moderate wine consumption, and low consumption of non-fish meat products.
There is tentative evidence that the Mediterranean diet lowers the risk of heart disease and early death. Olive oil may be the main health-promoting component of the diet. There is preliminary evidence that regular consumption of olive oil may lower all-cause mortality and the risk of cancer, cardiovascular disease, neurodegeneration, and several chronic diseases.
Although there are many different “Mediterranean diets” among different countries and populations of the Mediterranean basin, because of ethnical, cultural, economical and religious diversities, the distinct Mediterranean diets generally include the same key components, in addition to regular physical activity:
High intakes of extra virgin olive oil (as the principal source of fat), vegetables (including leafy green vegetables), fresh fruits (consumed as desserts or snacks), cereals (mostly wholegrains), nuts and legumes.
Moderate intakes of fish (especially marine blue species), seafood, poultry, dairy products (principally cheese and yogurt) and red wine (with the exception of Muslim populations).
Low intakes of eggs, red meat, processed meat and sweets.
Total fat in this diet is 25% to 35% of calories, with saturated fat at 8% or less of calories.
A 2011 systematic review found that a Mediterranean diet appeared to be more effective than a low-fat diet in bringing about long-term changes to cardiovascular risk factors, such as lowering cholesterol level and blood pressure. A 2013 Cochrane review found limited evidence that a Mediterranean diet favorably affects cardiovascular risk factors. A meta-analysis in 2013 compared Mediterranean, vegan, vegetarian, low-glycemic index, low-carbohydrate, high-fiber, and high-protein diets with control diets. The research concluded that Mediterranean, low-carbohydrate, low-glycemic index, and high-protein diets are effective in improving markers of risk for cardiovascular disease and diabetes. However, concerns have been raised about the quality of previously performed systematic reviews and meta-analyses examining the impact of a Mediterranean diet on cardiovascular risk factors. Newer reviews have reached similar conclusions about the ability of a Mediterranean diet to improve cardiovascular risk factors such as high blood pressure.
The Mediterranean diet often is cited as beneficial for being low in saturated fat and high in monounsaturated fat and dietary fiber. One of the main explanations is thought to be the health effects of olive oil included in the Mediterranean diet. Olive oil contains monounsaturated fats, most notably oleic acid, which is under clinical research for its potential health benefits. The European Food Safety Authority Panel on Dietetic Products, Nutrition and Allergies approved health claims on olive oil, for protection by its polyphenols against oxidation of blood lipids and for the contribution to the maintenance of normal blood LDL-cholesterol levels by replacing saturated fats in the diet with oleic acid (Commission Regulation (EU) 432/2012 of 16 May 2012). A 2014 meta-analysis concluded that an elevated consumption of olive oil is associated with reduced risk of all-cause mortality, cardiovascular events and stroke, while monounsaturated fatty acids of mixed animal and plant origin showed no significant effects.
In 2014, two meta-analyses found that the Mediterranean diet was associated with a decreased risk of type 2 diabetes.
A meta-analysis in 2008 found that strictly following the Mediterranean diet reduced the risk of dying from cancer by 6%.
Another 2014 systematic review and meta-analysis found that adherence to the Mediterranean diet was associated with a decreased risk of death from cancer. There is preliminary evidence that regular consumption of olive oil may lower the risk of developing cancer.
A 2016 systematic review found a relation between greater adherence to a Mediterranean diet and better cognitive performance; it is unclear if the relationship is causal.
According to a 2013 systematic review, greater adherence to a Mediterranean diet is correlated with a lower risk of Alzheimer's disease and slower cognitive decline. Another 2013 systematic review reached similar conclusions, and also found a negative association with the risk of progressing from mild cognitive impairment to Alzheimer's, but acknowledged that only a small number of studies had been done on the topic.