The Mediterranean diet, known for its positive effects on health, owes this merit mainly to the use of olive oil as a fat of daily use, in contrast to the use of saturated fats of animal origin. It is no coincidence that 95% of the more than 750 million olive trees in the world are found in the countries of the Mediterranean basin.
The olive, a tree of civilisation
The olive tree originated about 20-40 million years ago, in the region corresponding to Italy and the eastern Mediterranean basin. The first domestication of this species occurred about 7,000 years ago in the Mediterranean regions.
The olive tree has long been considered sacred, as well as a symbol of wisdom, fertility, power, and purity. The olive branch is still today a symbol of abundance, glory, and peace, being often ritually offered to deities and powerful figures as emblem of benediction and purification. Olive oil has long been used not only as a food, fuel and cosmetic, but also for religious and ritual purposes.
Mediterranean diet: the Italian way of life
High intakes of extra virgin olive oil (as the principal source of fat) is the key feature of the Mediterranean diet, along with vegetables (including leafy green vegetables), fresh fruits (consumed as desserts or snacks), cereals (mostly whole grains), nuts and legumes.
In 2013, UNESCO added the Mediterranean diet to the Representative List of the Intangible Cultural Heritage of Humanity, with the following justification: "The Mediterranean diet involves 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".
The Mediterranean diet is often 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.
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.
Extra virgin olive oil: the nutraceutical for excellence
Extra-virgin olive oil is a phytocomplex, that is to say a product of vegetable origin containing a significant quantity of a wide range of components. Its beneficial effects on health are due to the biological action of these substances.
The main chemical component of olive oil is oleic acid, which is part of the category of mono-unsatured fatty acids, which are characterised by having only one double bond among all those present among the various carbon atoms; they differ in this from saturated fatty acids (which have only single bonds) and from polyunsaturated fatty acids (which instead have numerous double bonds). These fats are found in good quantities in olive oil and other vegetable oils. They are considered healthy fats, as they promote the reduction of LDL cholesterol present in the blood, which is cause of heart attacks and obstructions, and the increase of HDL cholesterol, which plays a protective action.
Oleic acid, a monounsaturated fatty acid, is certainly the main component of extra virgin olive oil. However, a small percentage of saturated fatty acids (palmitic and stearic) and a significant percentage of polyunsaturated fatty acids (linoleic and linolenic) are also present. The latter have a particular nutritional importance, since they can not be synthesised by our organism and must be supplied daily with the diet.
The presence of unsaturated bonds in fatty acids, though giving vegetable oils their peculiar biological qualities, makes them however also vulnerable to oxygen, determining the process of auto-oxidation, which is responsible for the formation of peroxides. This phenomenon proceeds with a speed proportional to the number of existing double bonds and is opposed by the nature and concentration of the anti-oxidant substances. In this respect, the unsaturation of fatty acids found in extra virgin olive is not too high, and numerous anti-oxidant substances that are presenti in this oil allow it to maintain an outstanding stability.
The above-mentioned anti-oxidant substances, together with other minor components, form part of the unsaponifiable fraction of olive oil. The in-depth study of the latter is revealing novelties of extreme interest for health, which only add to the irreplaceable role played by extra virgin olive oil in the Mediterranean diet, strengthening the reasons for its greater use. Therefore, the greater awareness of all consumers for the use of extra virgin olive oil has the main purpose of improving the health conditions of the populations and rewarding one of the most typical products of Italian agriculture and Puglia, considering that our region alone produces almost 10% of the entire world production of olive oil.
Among the antioxidant substances, in addition to linoleic and linolenic acids, tocopherols are certainly to be mentioned, represented by 90% of the alpha form, which is the most biologically active. Their content is about 150-170 mg/kg, and besides constituting an important stabilising element in the self-oxidation processes, they represent a valuable vitamin source.
The phenolic compounds perform another important anti-oxidant action. In this respect, extra virgin olive oil presents is particularly interesting because, in addition to alpha-tocopherol, it contains a series of phenolic acids and phenols in significant quantities. The combination of these substances determines a phenomenon of exaltation of stabilisation against oxidation, and this explains why the extra virgin olive oil is one of the fat substances that best resists to oxidative phenomena, both at room temperature and in heat treatments.
The amount of phytosterols in olive oil is peculiar: it is the only oil that has a particularly high concentration of beta-sitosterol, a substance that is opposed to intestinal absorption of cholesterol. Other phytosterols present are campesterol and lostigmasterol.
The hydrocarbons are partly saturated and partly unsaturated and are probably formed as collateral products during the synthesis of fatty acids. Among the hydrocarbons, we find the squalene, with hypocholesterolemic action, in large quantities (1.5 mg / kg) and beta-carotene, with a vitamin A and anti-oxidant action, in varying concentrations (0.3 - 3.7 mg/Kg).
Terpenic alcohols are present in both free and esterified forms with fatty acids. Of particular interest among these compounds is the cycloartenol, whose action favors the fecal excretion of cholesterol owing to an increase in the excretion of bile acids. It therefore contributes to the hypocholesterolemic action of extra virgin olive oil.
Phospholipids are present in not very high amounts and are represented by phosphatidicolin and phosphatidylethanolamine. They play a fundamental role in the protection of cell membranes, which are not simply the "wall" of cells, but above all the fulcrum of cellular exchanges and of the transmission of communication signals.
They are represented by carotenoids and chlorophyll. This pigment, whose quantity can vary in relation to various factors, biologically performs an action of excitement on the metabolism, of stimulation of cell growth and of blood production and of acceleration of the cicatrisation processes.
The aromatic substances are represented by numerous compounds, partly not yet identified, but which together contribute to create those particular organoleptic characteristics that positively influence digestion. In fact, it has been shown that, when the smell and taste of a food is enjoyed, the same composition of the gastric juice changes due to a higher concentration of pepsin, thus obtaining a better digestive activity.
Having known what is the "mixture" that makes up this wonderful phytocomplex, we can explain its biological importance for the protection of health and the prevention of diseases, especially degenerative ones.