How the Seven Countries Study contributed to the definition and development of the Mediterranean diet concept: a 50-year journey.

The Seven Countries Study of Cardiovascular Diseases was started at the end of the 1950s and it continues to be run after >50 years. It enrolled, at entry, 16 population cohorts in eight nations of seven countries for a total of 12,763 middle-aged men. It was the prototype of epidemiological studies seeking cultural contrasts and the first to compare cardiovascular disease (CVD) rates related to diet differences. The study has shown that populations suffer widely different incidence and mortality rates from coronary heart disease (CHD) as well as from other CVDs and overall mortality. Higher rates were found in North America and northern Europe, and lower rates in southern Europe - Mediterranean countries - and Japan. These differences in CHD rates were strongly associated with different levels of saturated fat consumption and average serum cholesterol levels, with lowest rates in Greece and Japan where the total fat intake was very different. The cohorts were also different in dietary patterns defined by the ratio of calories derived from plant foods and fish on the one hand and calories derived from animal foods and sugar on the other. These findings pointed to the so-called Mediterranean diet, which is characterized by large values of that plant/animal ratio, a pattern associated with lower incidence and mortality from CHD and also with the lowest death rates and the greatest survival rates. More recent studies have refined these concepts and documented on a larger scale the virtues of these eating habits.