The Mediterranean diet is now recognized as being both limited in toxicity and abundant in nutrient and non-nutrient protective factors. A large body of basic, clinical and epidemiological studies have been developed in recent years to provide evidence of the benefits of the Mediterranean diet or its components on health. Evidence-based medicine ranks randomized controlled clinical trials as providing the highest level of evidence and expert opinions the lowest. On the basis of these criteria, the current state of knowledge about Mediterranean diet in primary and secondary prevention of disease and mortality and morbidity as functions of the amount of alcoholic beverage consumption, is reviewed. Efficacy versus effectiveness, the role of basic and animal research, and bioavailability studies providing evidence is also discussed.