Although olive oil has been a staple food in the Mediterranean for thousands of years, it is only relatively recently that its goodness has come under medical scrutiny, to emerge with flying colours.
Olive oil is the principal dietary fat throughout most of the region, as far as the northern margins of the cultivation of the olive tree Olea Europea, where it is gradually replaced by solid animal fats such as butter, lard and goose fat. To the east, in Asia Minor, in parts of the Middle East, and into Asia, it is replaced by sesame and other nut and seed oils, and ghee (clarified butter), and to the south, in the African hinterland, by peanut, coconut and palm oils.
In the West, the culinary use of olive oil is now commonplace but its widespread availability is a fairly recent phenomenon. Although olive oil of acceptable quality is generally available in the large supermarkets and multiple stores at very reasonable prices, thanks to volume buying, specialist food stores and delicatessens stock a better range of extra virgin and blended oils from different countries, predominantly Italy, Spain and Greece.
Many health-conscious cooks now use olive oil almost to the exclusion of all other cooking fats, but it is important to recognize that processed, convenience and junk foods are a rich source of animal fat. Fat itself is not bad for you, but is an essential component of a healthy diet; it is the kind of fat you consume that matters. Fats can be mainly saturated, as animal fats and their derivatives are, polyunsaturated, like grape seed, sunflower, safflower and corn oils, and monoun-saturated, or they can be a combination. Doctors are increasingly recommending a reduction in our consumption of animal fats in favour of unsaturated vegetable fats and the oils present in some fish. Olive oil is low in saturated and polyunsaturated fats but very high in monounsaturates and there is now a wealth of evidence to support its alleged beneficial effects which would appear to suggest that we should consume a lot more of it.
It is known that eating cholesterol-rich foods and saturated (animal) fats raises blood cholesterol and that a high level of cholesterol in the blood over a long period increases the risk of cardiovascular disease. Fatty deposits of cholesterol called plaque build up slowly in the smooth lining of the blood vessels, narrowing their bore, roughening and hardening them (atherosclerosis), and so forcing the blood to flow at higher pressure, much as a gardener can increase the water pressure of a hose pipe by partially covering the hole with the thumb. Sometimes blood clots (thromboses) form where the blood comes into contact with these damaged surfaces of the vessel walls (atheromas), either blocking the vessel locally or breaking off and occluding a vessel downstream. A coronary thrombosis is a life-threatening condition in which the blockage of a coronary artery leads to the death of part of the heart muscle through starvation of oxygen-bearing blood to its tissue, an event known as a coronary infarction, or, in the vernacular, a heart attack. A thrombosis in the vessels supplying blood to the brain often results in a stroke, again through tissue death. Otherwise, sustained high blood pressure itself can lead to stroke and to kidney damage. Therefore, consumption of too much saturated fat is one factor which can lead to cardio vascular disease, as is chronic high blood pressure exacerbated by smoking, obesity and lack of exercise.
The link between dietary fat and health was established in comparative studies that were made of the effects of different national and regional diets on disease incidence: those societies that consume a lot of cholesterol and saturated fats, (such as Britain, parts of Scandinavia and the USA) show a high incidence of heart disease, while those with low levels of saturated fats in the diet and high levels of mono- and polyunsaturated fats (Southern Italy, Greece and other countries that produce and consume olive oil) have some of the lowest incidence in the world, as do certain regions with a diet rich in fish oils. It would appear that consumption of olive oil, which is very high in monounsaturated fat, actually reduces blood cholesterol. But it is not as simple as that, because one form of blood cholesterol ('high density lipoprotein') is thought to help clear away plaque and atheromas, whereas 'low density lipoprotein' cholesterol has the opposite, damaging effect of promoting them. While polyunsaturated fats in other vegetable oils such as safflower, sunflower and grape seed do generally reduce both types of cholesterol in the blood, only tats high in monounsaturates, such as olive oil, lower the harmful kind of cholesterol while stimulating the beneficial kind, an extraordinary miracle of targetting with thousands of years of intuitive experience behind it. There is also evidence that olive oil acts as an anticoagulant, thinning the blood in the same way that aspirin does, and this is proving to be an important therapy in the treatment of patients who have survived a heart attack.