The Mediterranean diet as a nutritional recommendation is different from the cultural practices that UNESCO listed in 2010 under the heading "Mediterranean diet" on the Representative List of the Intangible Cultural Heritage of Humanity: "a set of skills, knowledge, rituals, symbols and traditions concerning crops, harvesting, fishing, animal husbandry, conservation, processing, cooking, and particularly the sharing and consumption of food", not as a particular set of foods. Its sponsors include Italy, Spain, Portugal, Morocco, Greece, Cyprus, and Croatia.
The US 2015-2020 national guidelines devised a "Healthy Mediterranean-Style Eating Pattern", assessed against and mirroring the Mediterranean diet patterns and its positive health outcomes. It was designed from the "Healthy U.S.-Style Eating Pattern", but it contains more fruits and seafood, and less dairy.
The Mediterranean diet is included among dietary patterns that may reduce the risk of cardiovascular diseases. A 2013 Cochrane review found limited evidence that a Mediterranean diet favorably affects cardiovascular risk factors. A 2013 meta-analysis 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, while there was limited evidence for an effect of vegetarian diets on glycemic control and lipid levels unrelated to weight loss. However, reviews of early 2016 have been more cautious: concerns were raised about the quality of previous systematic reviews examining the impact of a Mediterranean diet on cardiovascular risk factors, further standardized research has been found to be necessary, and the evidence for the possible prevention of vascular disease by the Mediterranean diet was "limited and highly variable". Reviews in 2016-17 reached similar conclusions about the ability of a Mediterranean diet to improve cardiovascular risk factors, such as lowering the risk for hypertension and other cardiovascular diseases.
The Mediterranean diet is low in saturated fat with high amounts of monounsaturated fat and dietary fiber. One possible factor is the potential health effects of olive oil 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. The American Heart Association discussed the Mediterranean diet as a healthy dietary pattern that may reduce the risk of cardiovascular diseases.
In 2014, two meta-analyses found that the Mediterranean diet was associated with a decreased risk of type 2 diabetes, findings similar to those of a 2017 review. The American Diabetes Association and a 2019 review indicated that the Mediterranean diet is a healthy dietary pattern that may reduce the risk of diabetes.
A meta-analysis in 2008 found that strictly following the Mediterranean diet was correlated with a decreased risk of dying from cancer by 6%. Another 2014 review found that adherence to the Mediterranean diet was associated with a decreased risk of death from cancer. A 2017 review found a decreased rate of cancer, though evidence was weak.
Weight loss in obesity
In a 2019 review, the Mediterranean diet was discussed as a dietary pattern that may help obese people lower the quantity and improve the nutritional quality of food intake, with an overall effect of possibly losing body weight.
A scan of a brain on the Mediterranean diet (left) showing the effects of a vegetable based diet on the ventricles, white matter, and mass of the brain versus a scan of a normal brain (right).
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.
Major depressive disorder
There is a correlation between adherence to the Mediterranean diet and a lower risk of depression. Studies on which these correlations are made, are observational and do not prove cause and effect.
As the Mediterranean diet usually includes products containing gluten like pasta and bread, increasing use of the diet may have contributed to the growing rate of gluten-related disorders.
There is some evidence that a greater adherence to the Mediterranean diet is associated with longer telomeres.
The Mediterranean Diet Pyramid, summarizing the pattern of eating associated with this diet
There are variations of the "Mediterranean diets" in different countries and among the individual populations of the Mediterranean basin, due to ethnic, cultural, economic and religious diversities. The "Mediterranean diet" as defined by dietitians generally includes the following components, which are not typical of diets in the Mediterranean basin:
High intakes of olive oil (as the principal source of fat), vegetables (including leafy green vegetables), fresh fruits (consumed as desserts or snacks), cereals (mostly whole grains), nuts and legumes.
Moderate intakes of fish and other seafood, poultry, dairy products (principally cheese and yogurt) and red wine.
These proportions are sometimes represented in the Mediterranean Diet Pyramid. In a diet with roughly this composition, the fat content accounts for 25% to 35% of the total intake of calories, while the amount of saturated fat is, at most, 8% of the calorie content.
In contrast to the dietary recommendation, olive oil is not the staple fat in much of the Mediterranean basin: in northern and central Italy, lard and butter are commonly used in cooking, and olive oil is reserved for dressing salads and cooked vegetables; in both North Africa and the Middle East, sheep's tail fat and rendered butter (samna) are traditional staple fats.
Comparison of dietary recommendations for three Mediterranean diet plans
The concept of a Mediterranean diet was developed to reflect "food patterns typical of Crete, much of the rest of Greece, and Italy in the early 1960s". Although it was first publicized in 1975 by the American biologist Ancel Keys and chemist Margaret Keys (his wife and collaborator), the Mediterranean diet failed to gain widespread recognition until the 1990s. Objective data showing that Mediterranean diet is healthful originated from results of epidemiological studies in Naples and Madrid, confirmed later by the Seven Countries Study first published in 1970, and a book-length report in 1980.
The most commonly understood version of the Mediterranean diet was presented, among others, by Walter Willett and colleagues of Harvard University's School of Public Health since the mid-1990s. The Mediterranean diet is based on a paradox: although the people living in Mediterranean countries tend to consume relatively high amounts of fat, they have far lower rates of cardiovascular disease than in countries like the United States where similar levels of fat consumption are found. A parallel phenomenon is known as the French Paradox. By 2011, the Mediterranean diet was included by some authors as a fad diet promoted for losing weight. As of 2018, the value of the traditional Mediterranean diet was questioned due to homogenization of dietary choices and food products in the global economy, yet clinical research activity remained high, with favorable outcomes reported for various disease conditions, such as metabolic syndrome.
When Ancel Keys and his team of researchers studied and characterized the Mediterranean diet and compared it with the eating habits of the US and the most developed countries during that period, some identified it as the "Diet of the Poor". According to the famed Portuguese gastronomist Maria de Lourdes Modesto who met with Keys, Portugal was included in their observations and studies, and according to their conversation, Keys considered Portugal had the most pure "Mediterranean" diet. However, Salazar, the dictator of Portugal, did not want the name of Portugal included in what he understood as the diet of the poor.
Still today the name of the diet is not consensual among Portuguese gastronomists. After the Mediterranean diet became well-known, some studies evaluated the health benefits of the so-called "Atlantic diet", which is similar to Keys' "Mediterranean" diet, but with more fish, seafood, and fresh greens. Virgílio Gomes, a Portuguese professor and researcher on food history and gastronomy says, Portuguese cuisine is really an "Atlantic cuisine".
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