title: Vegetable consumption and colorectal cancer risk: an evaluation based on a systematic review and meta-analysis among the Japanese population.
abstract: OBJECTIVE
  The association between vegetable consumption and colorectal cancer risk remains unclear and may differ by region. We performed a systematic review and meta-analysis of epidemiologic studies on this issue among the Japanese population.
  
  
  METHODS
  A systematic review and meta-analysis was performed by searching MEDLINE through PubMed and the Ichushi database for cohort and case-control studies that were published by the end of December 2014. Associations were evaluated based on their magnitude and the strength of the evidence. Meta-analysis was performed by using the random effects model to estimate the summary relative risk with 95% confidence interval according to the study design. The final judgment was made based on a consensus of the research group members with consideration for both epidemiological evidence and biological plausibility.
  
  
  RESULTS
  We identified six cohort studies and 11 case-control studies on vegetable intake and colorectal cancer among the Japanese population. Of the cohort studies, one study showed a weak inverse association with colon cancer and another study showed a weak positive association with rectal cancer in men, but other studies found no associations between vegetable consumption and colon and rectal cancers. With regard to case-control studies, one study found a strong inverse association with colon cancer, and three studies showed a weak-to-strong inverse association with rectal cancer. In meta-analysis, the summary relative risk (95% confidence interval) for the highest vs. the lowest categories of vegetable consumption were 1.00 (0.92-1.10) and 0.75 (0.59-0.96) for cohort and case-control studies, respectively.
  
  
  CONCLUSIONS
  There was insufficient evidence to support an association between intake of vegetables and the risk of colorectal cancer among the Japanese population.
authors.affiliation: Department of Epidemiology and Prevention, Center for Clinical Sciences, National Center for Global Health and Medicine, Tokyo.
authors.forename: Ikuko
authors.initials: I
authors.lastname: Kashino
authors.affiliation: Department of Epidemiology and Prevention, Center for Clinical Sciences, National Center for Global Health and Medicine, Tokyo mizoue@ri.ncgm.go.jp.
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Mizoue
authors.affiliation: Department of Preventive Medicine, Faculty of Medicine, Saga University, Saga.
authors.forename: Keitaro
authors.initials: K
authors.lastname: Tanaka
authors.affiliation: Division of Epidemiology, Department of Public Health and Forensic Medicine, Tohoku University Graduate School of Medicine, Sendai.
authors.forename: Ichiro
authors.initials: I
authors.lastname: Tsuji
authors.affiliation: Department of Public Health, Hokkaido University Graduate School of Medicine, Sapporo.
authors.forename: Akiko
authors.initials: A
authors.lastname: Tamakoshi
authors.affiliation: Department of Preventive Medicine, Kyushu University Faculty of Medical Sciences, Fukuoka.
authors.forename: Keitaro
authors.initials: K
authors.lastname: Matsuo
authors.affiliation: Department of Preventive Medicine, Nagoya University Graduate School of Medicine, Nagoya.
authors.forename: Kenji
authors.initials: K
authors.lastname: Wakai
authors.affiliation: Department of Epidemiology and Preventive Medicine, Gifu University Graduate School of Medicine, Gifu.
authors.forename: Chisato
authors.initials: C
authors.lastname: Nagata
authors.affiliation: Epidemiology and Prevention Division, Research Center for Cancer Prevention and Screening, National Cancer Center, Tokyo AXA Department of Health and Human Security, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.
authors.forename: Manami
authors.initials: M
authors.lastname: Inoue
authors.affiliation: Epidemiology and Prevention Division, Research Center for Cancer Prevention and Screening, National Cancer Center, Tokyo.
authors.forename: Shoichiro
authors.initials: S
authors.lastname: Tsugane
authors.affiliation: Epidemiology and Prevention Division, Research Center for Cancer Prevention and Screening, National Cancer Center, Tokyo.
authors.forename: Shizuka
authors.initials: S
authors.lastname: Sasazuki
mesh_terms: D000368:Aged; D044466:Asian People; D016022:Case-Control Studies; D015331:Cohort Studies; D015179:Colorectal Neoplasms / Q000453:epidemiology*; D004032:Diet; D005247:Feeding Behavior; D006801:Humans; D015994:Incidence; D007564:Japan / Q000453:epidemiology; D008297:Male; D012306:Risk; D014675:Vegetables
keywords: Japanese; colorectal cancer; epidemiology; systematic review; vegetable