The Mediterranean diet story illustrates that "why" questions are as important as "how" questions in disease explanation.

The discovery of the cardioprotective properties of the Mediterranean diet is one of the great successes of epidemiology, and as a result elites around the globe now regularly consume Mediterranean products like olive oil. Although biochemical, clinical, and epidemiological studies have at least partly revealed how various components of this diet may protect the cardiovascular system, the reasons why this protection is conferred by a "Mediterranean" but not by many other European diets have not received so much attention. A plausible hypothesis is that, because of a combination of physico-geographical and socioeconomic circumstances, the variety of plant and animal food traditionally consumed by populations on the European shores of the Mediterranean Sea is relatively similar to that of the food available to the hunter-gatherers from whom we descend. Our organ systems have evolved to work optimally on such a diet, and have not had the chance to adapt to a diet containing, for example, more saturated fats and trans fatty acids, and less antioxidants and fiber. Understanding why the Mediterranean diet is cardioprotective is important for finding dietary solutions within the physico-geographical and socioeconomic constraints of the areas in which populations actually live, for example, by taking advantage of the cardioprotective properties of their traditional diets. This may in the longer run lead to a more sustainable approach to cardiovascular disease prevention.