The Seven Countries Study in Crete: olive oil, Mediterranean diet or fasting?

In the December 2004 issue of your journal, in his Out of the Box column, Geoffrey Cannon referred to Ancel Keys’ Seven Countries Study and the fact that Keys and his colleagues seemed to have ignored the possibility that Greek Orthodox Christian fasting practices could have influenced the dietary habits of male Cretans in the 1960s. For this reason, we had a personal communication with Professor Christos Aravanis, who was responsible for carrying out and following up the Seven Countries Study in Greece. Professor Aravanis confirmed (Aravanis C, personal communication) that, in the 1960s, 60% of the study participants were fasting during the 40 days of Lent, and strictly followed all fasting periods of the church according to the Greek Orthodox Church dietary doctrines. These mainly prescribe the periodic abstention from meat, fish, dairy products, eggs and cheese, as well as abstention from olive oil consumption on certain Wednesdays and Fridays. However, it is indeed the case that this was not noted in the study, and no attempt was made to differentiate between fasters and non-fasters. In our view this was a remarkable and troublesome omission. The Greek Orthodox Church prescribes almost 180 days of fasting per year. It is unknown to what extent the Cretans who were the original subjects of the Seven Countries Study and who fasted during Lent also followed the precepts of their Church throughout the year, and thus on how many days in total and to what extent the Cretan participants of the Seven Countries Study fasted. Therefore, it still remains unknown whether the results of the Seven Countries Study in Crete, which have been very widely cited and have crucially influenced dietary guidelines and industrial practices all over the world, were about olive oil in particular, the Mediterranean diet in general – or the beneficial effects of fasting in the sense of regular restriction of certain foods, notably those of animal origin. Nevertheless, from our own recent studies, we are sure that the effects on serum lipids and longevity of fasting according to Greek Orthodox Church practices would have been significant, if relative data had been made available in the Seven Countries Study. Geoffrey Cannon was right to propose this.