The mediterranean diet is a lifestyle that has existed in Mesopotamia and the eastern Mediterranean region for five thousand years or more. The Mediterranean diet was scientifically defined for the first time in the 1960s by Angel Keys in a Seven Countries Study.
The traditional Mediterranean diet
The traditional Mediterranean diet is characterized with high consumption of vegetables, fruits, olive oil, fish and seafood, herbs and spices, legumes, nuts and cereals (especially whole grains) but low consumption of red meat, moderate consumption of milk and wine with meals. Mediterranean diet, which was defined as a sustainable diet due to its environmental, nutritional, economic and sociocultural dimensions in a conference held in Italy in 2009; It was accepted as “The Intangible Cultural Heritage of Humanity” by UNESCO in 2010. The latest update of the Mediterranean diet pyramid in 2011, it reveals that the main concern is ultra-processed food. In the pyramid, not only nutrition-oriented approach, but also social, cultural, traditional and environmental determinants of food were added. Nutrition is not just about lowering of disease risk, but also includes factors such as the preparation, cooking and eating of the food.
The target group of Mediterranean diet pyramid recommendations is healthy individuals between the ages of 18-65. Suggestions given to individuals with any disease, pregnant women and children’s needs can be reshaped. All food groups are included in the Mediterranean diet pyramid. This diet, which has a rich food variety, minimizes the deficiency of a food group or nutrient. The consumption frequencies and portions of the recommended foods are included in the pyramid.
Plant-based foods constitute the basis of the Mediterranean food pyramid. The consumption of olive oil, which is the main oil source of the pyramid, whole grains (1-2 servings), fruits of various colors and textures (1-2 servings), vegetables (2 servings, cooked or raw) are recommended at every meal. Daily consumption of dairy products (2 servings, preferably low-fat) and nuts- seeds (1-2 servings) are recommended. The use of onion, garlic and various spices are recommended to reduce the amount of salt and increase flavor. In the pyramid, the consumption of potatoes, legumes and animal origin proteins are recommended weekly. It is recommended to consume 2 servings of legumes, 3 servings of potatoes and 2-4 servings of eggs per week. Recommended consumption of fish and seafoods are ≥2 servings, white meat is 2 servings and the amount of red meat is <2 servings per week. Processed red meat consumption should be less than 1 serving per week.
Foods which are at the top of the pyramid are rich in fat and sugar. Sugar, sweets, pastries, sweetened drinks and soft drinks should be consumed in small amounts and in special cases. The weekly consumption of such foods should be limited to 2 servings. The wine and other fermented beverages should be consumed with moderation and preferably during meals (1 glass per day for women, 2 glass per day for men.
The Mediterranean diet pyramid
In the Mediterranean diet pyramid, besides the nutritional importance of food, food has a cultural and social meaning. Cooking and sharing meals with family or friends around a table are among the suggestions highlighted in the pyramid. Consuming traditional and local products and seasonal fresh products are among the suggestions given in the pyramid. Finally, 30 minutes of moderate physical activity per day is recommended for a healthy body weight and balanced energy intake.
Food in The Mediterranean Diet
Fruits and vegetables that take part a large place in the Mediterranean diet contain phytochemicals with many antioxidant properties. Fruits and vegetables consumption have protective effect against chronic diseases and some types of cancer. It is thought that their content, the vitamins, minerals, fiber and various phytochemicals, has a positive effect on our health. Caroten which founds in red foods, has antioxidant and anti-inflammatory effects against reactive oxygen species and free radicals. Cooking techniques are effective on phytochemicals. While the amount of carotene increases by 36% with the stewing technique, which is often preferred as a cooking method in Mediterranean countries, it decreases by 41% in frying. To increase the bioavailability of carotenes, 3-5 grams of diet oil is recommended. Cruciferous vegetables (broccoli, cabbage, cauliflower), also known as Brasika, have important properties such as increasing cellular antioxidant dilution and reducing oxidative stress thanks to the glucosinolates they contain. It is recommended that these types of vegetables be consumed in a short time and cooked in little water.
According to a case-control study from Southern European countries, cooked and raw vegetables are protective against many types of cancer, while it has been stated that raw consumption has a greater protection. The findings of a meta-analysis of 95 epidemiological studies by Miller et al; it has been shown that cardiovascular events and stroke are reduced by 27% -39% if the consumption of fruits, vegetables and grains is 3-4 servings per day. Consumption of more one portion a day caused a 35% decrease in mortality. When looking at the results of a meta-analyses with 11 studies conducted in 7 European countries, a positive relationship was found between SES and fruit & vegetable consumption. As a result of the study, a higher daily intake of 24.3 grams of fruit was found in men individuals with the highest education level. This difference is 33.6 grams in women with the highest education level.
Legumes, which are recommended to be consumed weekly, have many effects on health. These foods, which contain many micro and macro nutrients, have positive effects on lipid profile, blood pressure and inflammation. Data from observational studies showed improvements in glucose metabolism and antioxidant capacity. These foods, which have a low glycemic index, are also good sources of protein and fiber.
Olive oil consumption, which is the main oil source of the Mediterranean diet, varies between 25-50 ml/day. Approximately 99% of the olive oil composition consists of triacylglycerols, while the remaining part consists of free fatty acids, mono and diacylglycerols. Olive oil, which contains high levels of monounsaturated fatty acids (MUFA) contains 80% oleic acid. Compared to polyunsaturated fatty acids (PUFA), the MUFA molecule becomes more resistant to oxidation since it contains a single double bond. This situation affects the stability of olive oil and extends its shelf life. Olive oil containing tocopherol, carotenoids and polypheneols has antioxidant and anti-inflammatory properties. There are at least 36 types of phenolic compounds identified in olive oil so far and the increase of these compounds is directly proportional to the increase in antioxidant capacity.
Data from clinical research showed improvements in inflammation markers and low density lipoprotein (LDL) as the concentration of polyphenols in olive oil increased. Olive oil is especially recommended in the Mediterrenean diet due to health effects of these compounds. Although total polyphenol concentrations vary according to the type and quality of the oil, it varies between 50-800 mg/kg. It should be added to the meal at the end of the cooking process to minimize the loss of these compounds during the process. The first study showing the health effects of olive oil consumption was a Seven-Country Study, followed by the MONICA. In these studies, it was stated that the incidence and mortality of cardiovascular diseases are lower in Mediterranean countries compared to other countries. In a study of 180 people with metabolic syndrome, the intervention group (n=90) was given the Mediterranean diet, while the control group (n=90) was given the standard diet (carbohydrates, 50%-60%; proteins, 15%- 20%; total fat , 30%). After 2 years, the patients following mediterranean diet group consumed more unsaturated fatty acids, fiber, fruits, vegetables and nuts. Compared to the intervention group and the control group, there was a decrease in the intervention group’s insulin resistance and an improvement in endothelial function.
Nuts and seeds, important components of the Mediterranean diet, have a protective effect against cardiovascular diseases and mortality. Most nuts are rich in unsatured fatty acids. Also, they are rich sources of protein, fiber, tocopherol, folate, magnesium and calcium. While MUFA is the predominant fatty acid in most of them, walnuts contain more PUFA. Nuts and seeds contain high amounts of l-arginine, which is the precursor of nitric oxide that regulates blood pressure. Nuts and seeds contain high amounts of polyphenols. This content is reduced by 50% or more after roasting or peeling of the outer membrane. Walnut consumption has the highest polyphenol content compared to other nuts and seeds, as it is mostly consumed raw and unshelled. They contain a group of non-cholesterol compounds known as plant sterols, or phytostreoles. These compounds inhibit the absorption of cholesterol and play an important role in lowering cholesterol in the blood.
In a prospective cohort study on women the relationship between type 2 diabetes and nuts&seeds consumption has examined, it was observed that the risk of type 2 diabetes has decreased when the amount of nuts&seeds consumption has increased.
In a study involving 583 women and men with hypercholesterolemia, total cholesterol concentrations decreased by 10.9 mg/dl in individuals who consumed 67 grams of nuts daily, while LDL cholesterol decreased by 10.2 mg/dl. A decrease of 20.6 mg/dl was observed in individuals with the lowest triglyceride level of 150 mg/dl.
The wine which is an important component of the Mediterranean diet has protective effect of regular and moderate consumption against cardiovascular risk, hypertension, atherosclerosis, type 2 diabetes and some cancers (e.g. prostate, colon, ovarian). In general, one glass (150 g of wine, 10 g of alcohol) is recommended for women, 2 glasses (300 g of wine, 20 g of alcohol) for men. The protective effect of red wine against cardiovascular diseases (CVD) is explained by many mechanisms. An example is a decrease in platelet collection with LDL cholesterol and an increase in insulin sensitivity.
As alcohol content (ethanol) increases in wine, there is an increase in high-density lipoprotein (HDL) cholesterol and a decrease in systemic inflammation. Thanks to its high polyphenol components, it is effective in lowering blood pressure, improving endothelial function and reducing inflammation (31). Due to resveratrol content of wine, there is a decrease in the accumulation of cholesterol in the aorta and plasma triglycerides. Another important compound, kuersetin, was noted to be hypertensive, having a vasodilator effect on smooth muscles.
Low consumption of red meat is an important part of the Mediterranean diet. Excessive consumption of processed meat has been associated with an increased risk of cancer, hypertension, Type 2 diabetes, metabolic syndrome and heart disease. Nitrite and nitrate, used as preservatives, have been found to lead to entodel disorder and insulin resistance when they are found in high amounts in the blood in adults. Excess saturated fat, cholesterol, and sodium lead to type 2 diabetes, metabolic syndrome, and CVD. The relationship between red meat and cancer depends on the cooking method, genetic characteristics, type and form of consumption. Polycyclic aromatic hydrocarbons (PAH) and heterocyclic aromatic amines may be formed responsible for the development of cancer depending on the temperature, duration and type of meat. The amount of PAH is also high in smoked and dried meats. Due to the high content of saturated fat, it also increases the formation of free radicals, causing the formation of cancer.
A large-scale cohort study from European countries found that high consumption of processed red meat leads to an increased risk of CVD, cancer and early death. When red meat consumption has decreased by 20 g/day in the same population, deaths may be prevented by more than 3%. White meat consumption was not associated with all-cause mortality. A study on adherence to the Mediterranean diet concluded that as the meat consumption has increased in men and women the adherence decreased while adherence increased as consumption of fruits, vegetables, legumes, grains, fish and olive oil groups has increased.
Unlike other animal sources, more than 2 servings of fish per week are recommended in the Mediterranean diet pyramid. The fishes which make up 40% of total body fat with unsaturated fatty acids, also have a high protein content. Fish and seafood have a lower amount of saturated fat and cholesterol compared to meat (excluding crab, lobster, shrimp and oysters). By enzymatic denaturation processes of α-linoleic acid found in fish and seafood, it is first converted to eicosapentaenoic acid (EPA) and then to docosahexaenoic acid (DHA). DHA and EPA which are anti-inflammatory are precursors to prostaglandins, thromboxanes and leukotrins. They have an antithrombotic effect and reducing blood clotting and lowering LDL cholesterol.