Abstract
BACKGROUND: A series of recent reports from large-scale cohort studies involving more than 100,000 subjects reported no or only very small inverse associations between fruit and vegetable intake and overall cancer incidence, despite having sufficient power to do so. To date, however, no such data have been reported for Asian populations. OBJECTIVE: To provide some indication of the net impact of fruit and vegetable consumption on overall cancer prevention, we examined these associations in a pooled analysis of large-scale cohort studies in Japanese populations. METHODS: We analyzed original data from four cohort studies that measured fruit and vegetable consumption using validated questionnaires at baseline. Hazard ratios (HRs) in the individual studies were calculated, with adjustment for a common set of variables, and combined using a random-effects model. RESULTS: During 2,318,927 person-years of follow-up for a total of 191,519 subjects, 17,681 cases of overall cancers were identified. Consumption of fruit or vegetables was not associated with decreased risk of overall cancers: corresponding HRs for the highest versus lowest quartiles of intake for men and women were 1.03 (95% CI, 0.97-1.10; trend p = 1.00) and 1.03 (95% CI, 0.95-1.11; trend p = 0.97), respectively, for fruit and 1.07 (95% CI, 1.01-1.14; trend p = 0.18) and 0.98 (95% CI, 0.91-1.06; trend p = 0.99), respectively, for vegetables, even in analyses stratified by smoking status and alcohol drinking. CONCLUSIONS: The results of this pooled analysis do not support inverse associations of fruit and vegetable consumption with overall cancers in the Japanese population.