title: Dietary fiber intake and risk of colorectal cancer: a pooled analysis of prospective cohort studies.
abstract: BACKGROUND
  Inconsistent findings from observational studies have continued the controversy over the effects of dietary fiber on colorectal cancer.
  
  
  OBJECTIVE
  To evaluate the association between dietary fiber intake and risk of colorectal cancer.
  
  
  METHODS
  From 13 prospective cohort studies included in the Pooling Project of Prospective Studies of Diet and Cancer, 725,628 men and women were followed up for 6 to 20 years across studies. Study- and sex-specific relative risks (RRs) were estimated with the Cox proportional hazards model and were subsequently pooled using a random-effects model.
  
  
  METHODS
  Incident colorectal cancer.
  
  
  RESULTS
  During 6 to 20 years of follow-up across studies, 8081 colorectal cancer cases were identified. For comparison of the highest vs lowest study- and sex-specific quintile of dietary fiber intake, a significant inverse association was found in the age-adjusted model (pooled RR = 0.84; 95% confidence interval [CI], 0.77-0.92). However, the association was attenuated and no longer statistically significant after adjusting for other risk factors (pooled multivariate RR = 0.94; 95% CI, 0.86-1.03). In categorical analyses compared with dietary fiber intake of 10 to <15 g/d, the pooled multivariate RR was 1.18 (95% CI, 1.05-1.31) for less than 10 g/d (11% of the overall study population); and RR, 1.00 (95% CI, 0.85-1.17) for 30 or more g/d. Fiber intake from cereals, fruits, and vegetables was not associated with risk of colorectal cancer. The pooled multivariate RRs comparing the highest vs lowest study- and sex-specific quintile of dietary fiber intake were 1.00 (95% CI, 0.90-1.11) for colon cancer and 0.85 (95% CI, 0.72-1.01) for rectal cancer (P for common effects by tumor site = .07).
  
  
  CONCLUSIONS
  In this large pooled analysis, dietary fiber intake was inversely associated with risk of colorectal cancer in age-adjusted analyses. However, after accounting for other dietary risk factors, high dietary fiber intake was not associated with a reduced risk of colorectal cancer.
authors.affiliation: Department of Nutrition, Harvard School of Public Health, Boston, Mass 02115, USA.
authors.forename: Yikyung
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authors.lastname: Park
authors.forename: David J
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authors.lastname: Hunter
authors.forename: Donna
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authors.lastname: Spiegelman
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authors.forename: Julie E
authors.initials: JE
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authors.forename: Charles S
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authors.lastname: Fuchs
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authors.forename: R Alexandra
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authors.lastname: Goldbohm
authors.forename: Saxon
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authors.lastname: Graham
authors.forename: Lisa
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authors.lastname: Harnack
authors.forename: Anne M
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authors.forename: Marjorie L
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authors.lastname: McCullough
authors.forename: Anthony B
authors.initials: AB
authors.lastname: Miller
authors.forename: Pirjo
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authors.lastname: Pietinen
authors.forename: Thomas E
authors.initials: TE
authors.lastname: Rohan
authors.forename: Arthur
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authors.lastname: Schatzkin
authors.forename: Walter C
authors.initials: WC
authors.lastname: Willett
authors.forename: Alicja
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authors.lastname: Wolk
authors.forename: Anne
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authors.lastname: Zeleniuch-Jacquotte
authors.forename: Shumin M
authors.initials: SM
authors.lastname: Zhang
authors.forename: Stephanie A
authors.initials: SA
authors.lastname: Smith-Warner
mesh_terms: D015179:Colorectal Neoplasms / Q000453:epidemiology* / Q000517:prevention & control; D004043:Dietary Fiber; D005260:Female; D006801:Humans; D008297:Male; D016016:Proportional Hazards Models; D012306:Risk