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The Mediterranean diet is a modern nutritional recommendation originally inspired by the traditional dietary patterns of Greece, Southern Italy, and Spain. 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 meat and meat products.
|“||While there were similarities between the countries, there are also important differences in the food habits of the Mediterranean countries. Neighbouring countries' food habits are closer than those on opposite sides of the Mediterranean Sea.... There is no single ideal Mediterranean diet.||”|
Despite its name, this diet is not typical of all Mediterranean cuisine. In Northern Italy, for instance, 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 the traditional staple fats, with some exceptions. Indeed, one researcher concludes: "It appears that currently there is insufficient material to give a proper definition of what the Mediterranean diet is or was in terms of well defined chemical compounds or even in terms of foods.... The all embracing term 'Mediterranean diet' should not be used in scientific literature...."
The most commonly understood version of the Mediterranean diet was presented, among others, by Dr Walter Willett of Harvard University's School of Public Health from the mid-1990s on. Based on "food patterns typical of Crete, much of the rest of Greece, and southern Italy in the early 1960s", this diet, in addition to "regular physical activity," emphasizes "abundant plant foods, fresh fruit as the typical daily dessert, olive oil as the principal source of fat, dairy products (principally cheese and yogurt), and fish and poultry consumed in low to moderate amounts, zero to four eggs consumed weekly, red meat consumed in low amounts, and wine consumed in low to moderate amounts". Total fat in this diet is 25% to 35% of calories, with saturated fat at 8% or less of calories.
Olive oil is part of the Mediterranean diet, though not of all Mediterranean cuisines: in Egypt, Malta, and Israel, olive oil consumption is negligible, and in other areas, it is not predominant. It contains a very high level of monounsaturated fats, most notably oleic acid, which epidemiological studies suggest may be linked to a reduction in coronary heart disease risk. There is also evidence that the antioxidants in olive oil improve cholesterol regulation and LDL cholesterol reduction, and that it has other anti-inflammatory and anti-hypertensive effects.
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 healthy first originated from the Seven Countries Study, with first publication in 1970, and a book-length report in 1980.
The Mediterranean diet is based on what from the point of view of mainstream nutrition is considered a paradox: that 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.
A number of diets have received attention, but the strongest evidence for a beneficial health effect and decreased mortality after switching to a largely plant based diet comes from studies of Mediterranean diet, e.g. from the NIH-AARP Diet and Health Study.
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.
Dietary factors are only part of the reason for the health benefits enjoyed by certain Mediterranean cultures. A healthy lifestyle (notably a physically active lifestyle or labour) is also beneficial. Environment may also be involved. However, on the population level, i.e. for the population of a whole country or a region, the influence of genetics is rather minimal, because it was shown that the slowly changing habits of Mediterranean populations, from a healthy active lifestyle and Mediterranean diet to a not so healthy, less physically active lifestyle and a diet influenced by the Western pattern diet, significantly increases risk of heart disease. There is an inverse association between adherence to the Mediterranean diet and the incidence of fatal and non fatal heart disease in initially healthy middle aged adults in the Mediterranean region.
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.
The putative benefits of the Mediterranean diet for cardiovascular health are primarily correlative in nature; while they reflect a very real disparity in the geographic incidence of heart disease, identifying the causal determinant of this disparity has proven difficult. The most popular dietary candidate, olive oil, has been undermined by a body of experimental evidence that diets enriched in monounsaturated fats such as olive oil are not atheroprotective when compared to diets enriched in either polyunsaturated or even saturated fats. A recently emerging alternative hypothesis to the Mediterranean diet is that differential exposure to solar ultraviolet radiation accounts for the disparity in cardiovascular health between residents of Mediterranean and more northerly countries. The proposed mechanism is solar UVB-induced synthesis of Vitamin D in the oils of the skin, which has been observed to reduce the incidence of coronary heart disease, and which rapidly diminishes with increasing latitude. Interestingly, residents of the Mediterranean are also observed to have very low rates of skin cancer (which is widely believed to be caused by over-exposure to solar UV radiation); incidence of melanomas in the Mediterranean countries is lower than in Northern Europe and significantly lower than in other hot countries such as Australia. Its been hypothesized that some components of the Mediterranean diet may provide protection against skin cancer.
Fruits and Vegetables: Mediterranean Diet provides 6-12 servings per day (Canada Food Guide recommends 7-10) This satisfies the Canada Food Guide
Grain Products: Mediterranean Diet provides 4-6 servings per day (Canada Food Guide recommends 6-8) This does not satisfy the Canada Food Guide
Milk and Alternatives: Mediterranean Diet provides 1-3 servings of low fat dairy products per day (Canada Food Guide recommends 2) This satisfies the Canada Food Guide
Meat and Alternatives: Mediterranean Diet provides 1-2 servings of poultry, fish and shellfish per day (Canada Food Guide recommends 2-3) This does not satisfy the Canada Food Guide
Other: Mediterranean Diet recommends one glass of red wine daily (Not mentioned in Canada Food Guide)
A meta-analysis published in BMJ in 2008 showed that following strictly the Mediterranean diet reduced the risk of dying from cancer and cardiovascular disease as well as the risk of developing Parkinson's and Alzheimer's disease. The results report 9%, 9%, and 6% reduction in overall, cardiovascular, and cancer mortality respectively. Additionally a 13% reduction in incidence of Parkinson's and Alzheimer's diseases is to be expected provided strict adherence to the diet is observed.
A 2010 meta-analysis published in the The American Journal of Clinical Nutrition found that the Mediterranean diet conferred a significant benefit with regard to the risk of chronic diseases, such as cardiovascular disease and cancer.
A 2011 meta-analysis published in the Journal of the American College of Cardiology analyzed the results of 50 studies (35 clinical trials, 2 prospective and 13 cross-sectional) covering about 535,000 people to examine the effect of a Mediterranean diet on metabolic syndrome. The researchers reported that a Mediterranean diet is associated with lower blood pressure, blood sugar, and triglycerides.
A meta-analysis published in the American Journal of Clinical Nutrition 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.
In 2014, two meta-analyses found that adherence to a Mediterranean diet was associated with a decreased risk of type 2 diabetes. Another 2014 systematic review and meta-analysis found that adherence to the Mediterranean diet was associated with a decreased risk of cancer mortality.
The name "Mediterranean diet" is not accepted in Portugal. 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". The Southern European Atlantic Diet is the traditional diet of Northern Portugal and Galicia (Spain) has been associated with a lower risk of non-fatal acute myocardial infarction.
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