Background: Epidemiological evidence for the impact of fruit and vegetable intake on breast cancer risk among the Japanese populations is scarce.
Objective: The purpose of this study was to evaluate the association between fruit and vegetable intake and breast cancer risk among 47,289 Japanese women.
Design: The study was conducted under a population-based prospective cohort design. Dietary assessment was performed using a validated food frequency questionnaire. A Cox proportional hazards regression model was used to calculate relative risks (RRs) and their corresponding 95 % confidence intervals (CIs).
Results: During an average of 10.2 years of follow-up, 452 cases of breast cancer were newly diagnosed. No association with breast cancer risk was seen for intake of total fruits and vegetables, cruciferous vegetables, green-leaf vegetables, yellow vegetables, or tomato products in overall or postmenopausal women. Cruciferous vegetable intake was associated with a statistically significant decrease in risk of premenopausal breast cancer [multivariable-RRQ4 vs. Q1 = 0.64 (95 % CI = 0.38-1.10; p trend = .046)] and showed a marginally inverse association with ER+ PR+ tumors [RRper 100 g increment = 0.64 (95 % CI = 0.41-1.00)]. In contrast, positive associations were seen between intake of total fruits and citrus fruits and breast cancer risk in overall and premenopausal women. However, these associations for fruit were all attenuated with additional adjustment for vitamin C intake.
Conclusions: Our results suggest an overall null association between total fruit and vegetable intake and breast cancer risk. Intake of cruciferous vegetable showed a statistically significant association with a decreased risk of breast cancer among premenopausal women.