Mediterranean Diets

Francesco Visioli, Ph.D.
Visiting Scientist

The Mediterranean diet was first described by Leland Allbaugh, thanks to funding from the Rockefeller Foundation, and then popularized by an American investigator, Dr. Ancel Keys, who, in the early 1950s, moved to Southern Italy, where he realized that mortality from coronary heart disease was extremely low. In fact, the term "Mediterranean diet" refers to the dietary profile of people in the Mediterranean area in that period. Since then, the Mediterranean diet has been gaining popularity in North America, where the consumption of traditional Mediterranean foods, such as olive oil and wine, is increasing steadily. 

My colleague, Artemis Simopoulos, and I recently edited a book entitled "Mediterranean Diets". The title itself suggests that there is no such thing as the Mediterranean diet. The populations in the Mediterranean area have different cultures, religions, economic prosperity, and education, and all these factors have some influence on dietary habits and health. Yet, a common dietary pattern can be identified that includes a high consumption of plant food (including carbohydrates and non-digestible fiber) rich in antioxidants, including vitamins, and the use of olive oil as the principal-or even exclusive-source of fat. 

The incidence of classic risk factors for coronary heart disease, such as high plasma cholesterol levels and high blood pressure, is not much different in the populations of the Mediterranean region compared to Western countries. This suggests that other, as yet unexplored, risk factors may be favorably affected by the components of the Mediterranean diet. Major emphasis has been placed on the low saturated fat content of this diet and on its high proportion of unsaturated fatty acids, especially those of the omega-3 series. Indeed, a high omega-3 intake has been shown to be protective against coronary heart disease, as also demonstrated by the DART and GISSI-Prevenzione clinical trials. 

A comparison of the dietary characteristics of southern Italy, Spain, and Maghreb (coastal northwestern Africa) strengthens the point that the Mediterranean diet is not a homogeneous nutritional model. For example, due to religious restrictions, alcohol intake is very low in Muslim countries, and cereal figures more prominently in the diet of those countries. 

The Lyon Heart Study was an intervention trial (first reported in 1993) in France that demonstrated that a diet resembling the Cretan diet, i.e. rich in plants and alpha-linolenic acid from canola oil, afforded better protection from the recurrence of myocardial infarction than the Step I American Heart Association prudent diet. 

In the Cretan diet, the intake of alpha-linolenic acid is high due to the consumption of herbs, walnuts, seeds, snails, purslane, and lamb. The Lyon Heart Study is important because it provides the first clinical proof of a protective effect of the Mediterranean diet on cardiovascular disease. 

People in Mediterranean countries consume more total fat than Northern European countries, but most of the fat is in the form of monounsaturated fatty acids from olive oil and omega-3 fatty acids from fish, vegetables, and certain meats like lamb, while consumption of saturated fat is kept to a minimum. The diet in Crete is fairly high in total fat (40% of total calories, almost exclusively provided by olive oil) yet affords a remarkable protection from coronary heart disease (and probably breast and colon cancers). One possible explanation for this is that the large proportion of omega-3 fatty acids-EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) from marine fish and alpha-linolenic acid from vegetable sources; antioxidants, including vitamins provided by plant foods; olive oil; and wine lower coronary risk even without affecting plasma cholesterol levels. Both olives and grapes are native to the Mediterranean area. The fluids from their fruits (i.e. olive oil and wine) are obtained through physical -not chemical-processes and thus retain all the chemical properties of the fruits. Indeed, extra virgin olive oil (the most tasty and, alas, the most expensive kind) contains a remarkable amount of phenolics that provide its strong taste and high stability. Such phytochemicals have been shown in several in vitro and some in vivo studies to be powerful antioxidants and to exert other, unpredicted, biological activities-boosting the immune response and inhibiting platelet aggregation-that may partly account for the salubrious effects of the Mediterranean diets. 

Wine also contains phytochemicals that have been thoroughly investigated for their potential effects on human health. A moderate consumption of wine, as in the Mediterranean area where wine is ingested only at mealtime, might afford protection against cardiovascular disease. Studies are continuing, and the harmful effects of excessive alcohol intake should not be overlooked. 

A close analysis of the different Mediterranean diets confirms that they share a common pattern that includes a high proportion of plant foods, a moderate consumption of wine, and the use of olive oil as the predominant source of fat. Although this diet does not appear to affect the traditional risk factors for atherosclerosis, such as high plasma cholesterol levels and high blood pressure, a large number of epidemiological studies and one clinical trial have demonstrated its effectiveness in reducing the incidence of coronary heart disease and certain cancers.

Last updated November, 2000

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