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Olive oil, high in monounsaturated fat and a good source of antioxidants, is the Mediterranean region's principal source of fat. It appears that various levels of total fat (where the fat was mostly olive oil) can be associated with the excellent health seen in the region at that time, give the low levels of chronic diseases and high adult life expectancy throughout much of the Mediterranean in the 1960's.
Evidence suggests that the traditional diets of southern Italy and many other parts of the Mediterranean region in the 1960's had 30 percent or less of total energy from fat. Data from Greece in the 1960's, however, indicate that the lifestyles prevailing in those years (see below) an intake of over 35 percent of total daily energy from fat was also compatible with good health. Saturated fat was very low and most of the balance of fat in the diet came from monounsaturated fat in olive oil.
The Seven Countries Study reported that men in rural Crete in 1960 were apparently safely consuming 40 percent of their energy (calories) in the form of fat, following this pattern: 29 percent monounsaturated fat, 8 percent saturated fat, and 3 percent polyunsaturated fat. Regardless of varying fat levels, this proportional mix of types of fat in the diet - or fat profile- was typical of the Mediterranean region prior to significant shifts in eating habits over the last 30 years towards increased amounts of meat and dairy products.
In the early 1960's, heart disease rates in the Greek population were found to be nearly 90 percent lower than those measured among U.S. cohorts (Greece had 48 deaths per 100,000 population from ischemic heart disease in men aged 50 to 54, while the United States had 466). At this same time, rates of other chronic diseases were similarly low throughout Greece (breast cancer rates, for example, were one-fourth as low as those of Japan), and Greek male adult life expectancy was the highest in the world. Further, rates of most chronic diseases now thought to be diet-related were lower in Greece than in other Mediterranean countries. Apparently, for an active person with no weight problem, a traditional Mediterranean diet as represented by Crete with over 35 percent of energy from fat is compatible with excellent health.
For more than 30 years, researchers have known that the high intake of fat in the form of olive oil in the traditional Greek diet did not have any apparent negative health consequences. In the 1960's, researchers believed that olive oil with its high level of monounsaturated fat was neutral with respect to efforts on serum cholesterol and consequently they did not further explore its possible health-promoting potential. Current research into the relation between diet and blood levels of HDL-cholesterol (which is protective against coronary heart disease) sheds new light on the role of olive oil in the traditional Mediterranean diet. In many studies, replacing carbohydrates with olive oil increases HDL-cholesterol. It might be speculated that the higher fat level and fat profile of some traditional Mediterranean diets may have been protective, not just neutral. On the other hand, in a context such as that which exists in parts of Asia- where for whole populations high in complex carbohydrates but very low in total fat are associated with very low total cholesterol levels and coronary heart disease rates-this HDL phenomenon appears not to have adverse consequences on public health.
Future research may determine whether two of the basic varieties of the Mediterranean diet have equally good effects on health. The two are:
* High intakes of complex carbohydrates (cereals), with moderate intakes of olive oil, fruits and vegetables; and
* High intakes of olive oil, fruits and vegetables, with more moderate intakes of complex carbohydrates (cereals).
Olive oil should always replace- and not be added to- other sources of fat, especially butter and margarine. Butter is rarely featured in the traditional diets of Crete, southern Italy and much of the rest of the Mediterranean region in 1960. Margarine was completely unknown in the area until recently.
The value of using olive oil in preference to other plant oils, particularly those high in polyunsaturated fats, is based on the following considerations.
* High intakes of linoleic acid, the main polyunsaturated fat in many vegetable oils, may compete with Omega-3 fatty acids in biochemical processes and enhance the tendency of blood clot;
* Some research has indicated that diets high in monounsaturated fat are less likely to lead to LDL oxidation, and this may reduce atherosclerosis or the formation of atheroma;
* In many animal studies, diets high in polyunsaturated fats have promoted the development of tumors, although this has not been documented in humans;
* Mediterranean people have been using olive oil as their major dietary fat for thousands of years. Polyunsaturated fats have been set at higher levels on a wide sale for only a short time. Without evidence that lifetime exposure to high levels of polyunsaturated fats is safe, it is premature to recommend that diets high in these fats are as healthful-or safe- as, for example, the Mediterranean diet; and
* Olive oil contains several substances other than monounsaturated fatty acids and vitamin E, some of which may also contribute to tits apparent healthfulness.
Other populations with traditional low to very low levels of other plant oils in the diet- most notably those of parts of Asia-also have reduced risk of certain chronic disease. This suggests that there is probably more than one cultural model for healthy eating, and that these models may diverge substantially in levels of total fat intake, as suggested above, and type of plant oils used.
(c) 1998 Oldways Preservation & Exchange Trust
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