title: Fiber intake and risk of subsequent prostate cancer in Japanese men.
abstract: BACKGROUND
  Dietary fiber may reduce the risk of prostate cancer, possibly by increasing circulating concentrations of sex hormone-binding globulin and improving insulin sensitivity. However, results from previous epidemiologic studies of fiber intake and prostate cancer are inconsistent, and to our knowledge, no study has comprehensively evaluated the effects of soluble and insoluble fiber on prostate cancer in Asia.
  
  
  OBJECTIVE
  The objective was to examine the association between fiber intake and prostate cancer in Japanese men.
  
  
  METHODS
  We conducted a population-based prospective study in 43,435 Japanese men aged 45-74 y. Participants responded to a validated questionnaire, which included 138 food items. Follow-up was from 1995 through 2009. HRs and 95% CIs of incidence were calculated according to quartiles of fiber intake.
  
  
  RESULTS
  During the 11.6-y follow-up, of the 825 men newly diagnosed with prostate cancer, 213 had advanced-stage cancer, 582 had organ-localized disease, and 30 had an undetermined stage of disease. Among them, 217 cases were detected by subjective symptoms. Total fiber was not associated with total or advanced prostate cancer, with respective multivariable HRs for the highest and lowest quartiles of 1.00 (95% CI: 0.77, 1.29; P-trend = 0.97) and 0.67 (95% CI: 0.42, 1.07; P-trend = 0.30). Total fiber and insoluble fiber intake were associated with a decreased risk of advanced cancers detected by subjective symptoms, with multivariate HRs (95% CIs) across increasing quartiles of 1.00, 0.58, 0.62, and 0.44 (0.21, 0.92; P-trend = 0.05) for total fiber and 1.00, 0.60, 0.52, and 0.46 (0.22, 0.93; P-trend = 0.04) for insoluble fiber. Soluble fiber intake showed no association with prostate cancer.
  
  
  CONCLUSIONS
  Dietary fiber is inversely associated with advanced prostate cancer detected by subjective symptoms even among populations with relatively low intake, such as Japanese. These results suggest that a very low intake of dietary fiber is associated with an increased risk of prostate cancer.
authors.affiliation: From the Epidemiology and Prevention Group, Research Center for Cancer Prevention and Screening, National Cancer Center, Tokyo, Japan (NS, M Iwasaki, TY, TS, SS, M Inoue, and ST), and AXA Department of Health and Human Security, Graduate School of Medicine, University of Tokyo, Tokyo, Japan (M Inoue).
authors.forename: Norie
authors.initials: N
authors.lastname: Sawada
authors.affiliation: From the Epidemiology and Prevention Group, Research Center for Cancer Prevention and Screening, National Cancer Center, Tokyo, Japan (NS, M Iwasaki, TY, TS, SS, M Inoue, and ST), and AXA Department of Health and Human Security, Graduate School of Medicine, University of Tokyo, Tokyo, Japan (M Inoue).
authors.forename: Motoki
authors.initials: M
authors.lastname: Iwasaki
authors.affiliation: From the Epidemiology and Prevention Group, Research Center for Cancer Prevention and Screening, National Cancer Center, Tokyo, Japan (NS, M Iwasaki, TY, TS, SS, M Inoue, and ST), and AXA Department of Health and Human Security, Graduate School of Medicine, University of Tokyo, Tokyo, Japan (M Inoue).
authors.forename: Taiki
authors.initials: T
authors.lastname: Yamaji
authors.affiliation: From the Epidemiology and Prevention Group, Research Center for Cancer Prevention and Screening, National Cancer Center, Tokyo, Japan (NS, M Iwasaki, TY, TS, SS, M Inoue, and ST), and AXA Department of Health and Human Security, Graduate School of Medicine, University of Tokyo, Tokyo, Japan (M Inoue).
authors.forename: Taichi
authors.initials: T
authors.lastname: Shimazu
authors.affiliation: From the Epidemiology and Prevention Group, Research Center for Cancer Prevention and Screening, National Cancer Center, Tokyo, Japan (NS, M Iwasaki, TY, TS, SS, M Inoue, and ST), and AXA Department of Health and Human Security, Graduate School of Medicine, University of Tokyo, Tokyo, Japan (M Inoue).
authors.forename: Shizuka
authors.initials: S
authors.lastname: Sasazuki
authors.affiliation: From the Epidemiology and Prevention Group, Research Center for Cancer Prevention and Screening, National Cancer Center, Tokyo, Japan (NS, M Iwasaki, TY, TS, SS, M Inoue, and ST), and AXA Department of Health and Human Security, Graduate School of Medicine, University of Tokyo, Tokyo, Japan (M Inoue).
authors.forename: Manami
authors.initials: M
authors.lastname: Inoue
authors.affiliation: From the Epidemiology and Prevention Group, Research Center for Cancer Prevention and Screening, National Cancer Center, Tokyo, Japan (NS, M Iwasaki, TY, TS, SS, M Inoue, and ST), and AXA Department of Health and Human Security, Graduate School of Medicine, University of Tokyo, Tokyo, Japan (M Inoue).
authors.forename: Shoichiro
authors.initials: S
authors.lastname: Tsugane
mesh_terms: D000328:Adult; D000368:Aged; D015331:Cohort Studies; D004032:Diet / Q000009:adverse effects* / Q000208:ethnology; D004043:Dietary Fiber / Q000032:analysis / Q000627:therapeutic use*; D005500:Follow-Up Studies; D006306:Health Surveys; D006801:Humans; D015994:Incidence; D007564:Japan / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D011446:Prospective Studies; D011467:Prostate / Q000473:pathology; D011471:Prostatic Neoplasms / Q000453:epidemiology / Q000208:ethnology / Q000473:pathology / Q000517:prevention & control*; D012042:Registries; D012307:Risk Factors; D012995:Solubility
keywords: JPHC Study; Japanese men; fiber intake; prospective study; prostate cancer