Internationally, several studies have estimated the proportion of total cancer deaths attributable to various risk factors based on epidemiologic evidence [1, 2] , and various international guidelines and recommendations derived from these have appeared [3] [4] [5] [6] . Not surprisingly, domestic guidelines and recommendations for cancer prevention in Japan such as the 'Twelve recommendations for cancer prevention [7]' and 'Healthy People Japan 21 [8] ' have been significantly influenced by these reports.