Vegetables and fruit intake and cancer mortality in the Hiroshima/Nagasaki Life Span Study

Since the early 1980s, cancer has been the principal cause of death in Japanese men and women (Health Statistics Foundation, 2000). Although the total cancer mortality rate in Japan is similar to that of other developed countries, mortality rates for specific cancers differ widely. For example, in 2000, the mortality rate for stomach cancer was several-fold higher in Japan (Japan M: 31.2 per 100 000 population; F: 13.8) than in the US (M: 4.5; F: 2.3) or the UK (M: 10.1; F: 4.8); conversely, female breast cancer was up to three-fold lower in Japan than in Western countries (Japan: 7.7; US: 21.2; UK: 26.8) (Ferlay et al, 2001). Lifestyle, and in particular diet, has been hypothesised to explain partly the differences in these cancer rates between countries (Tominaga, 1985). Diet-related factors are thought to account for between 20 and 30% of all cancers (Doll and Peto, 1981). However, few specific dietary factors have been established, except for alcohol intake and cancers of the oral cavity, pharynx, larynx, oesophagus, liver, and breast, and salt intake and cancer of the stomach (World Health Organization, 1977; Smith-Warner et al, 1998). Fruit and vegetables have been considered to be as beneficial for several cancer sites, including cancers of the stomach, colon and rectum, lung, pancreas, and bladder, although the epidemiological evidence is inconsistent, particularly for hormone-dependent cancers such as the prostate and breast cancer (Branca et al, 2001). As longitudinal studies of vegetables and fruit and cancer in Japan are scarce (Hirayama, 1986; Kobayashi et al, 2002), this study aimed to examine the association between green-yellow vegetables and fruit consumption on the risk of the most common cancer deaths in a prospective cohort study in Japan.