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Original Contribution
December 14, 2005

Dietary Fiber Intake and Risk of Colorectal Cancer: A Pooled Analysis of Prospective Cohort Studies

Author Affiliations
 

Author Affiliations: Department of Nutrition (Drs Park, Giovannucci, Hunter, Willett, and Smith-Warner), Department of Epidemiology (Drs Buring, Colditz, Giovannucci, Hunter, Spiegelman, Willett, Smith-Warner, and Zhang), Department of Biostatistics (Dr Spiegelman), Harvard School of Public Health, Boston, Mass; Division of Preventive Medicine (Drs Buring and Zhang) and Channing Laboratory (Drs Colditz, Fuchs, Giovannucci, Hunter, and Willett), Department of Medicine, Brigham and Women’s Hospital and Harvard Medical School, Boston, Mass; Harvard Center for Cancer Prevention, Boston, Mass (Drs Coldtiz, Hunter, and Willett); Department of Adult Oncology, Dana-Farber Cancer Institute, Boston, Mass (Dr Fuchs); Department of Surgery and Centre for Clinical Research, Central Hospital, Västerås, Sweden (Dr Bergkvist); Epidemiology Unit, National Cancer Institute, Milan, Italy (Drs Berrino and Krogh); Department of Epidemiology, Maastricht University, Maastricht, the Netherlands (Dr van den Brandt); Department of Social and Preventive Medicine, University at Buffalo, State University of New York, Buffalo (Drs Freudenheim and Graham); Department of Epidemiology, TNO Nutrition and Food Research Institute, Zeist, the Netherlands (Dr Goldbohm); Division of Epidemiology, School of Public Health, University of Minnesota, Minneapolis (Drs Harnack and Jacobs); Risk Factor Monitoring and Methods Branch, Applied Research Program, Division of Cancer Control and Population Sciences, National Cancer Institute, Bethesda, Md (Ms Hartman); Karmanos Cancer Institute/Department of Pathology, Wayne State University, Detroit, Mich (Dr Kato); Nutritional Epidemiology Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Department of Health and Human Services, Bethesda, Md (Drs Leitzmann and Schatzkin); Epidemiology and Surveillance Research, American Cancer Society, Atlanta, Ga (Dr McCullough); Department of Public Health Sciences, University of Toronto, Toronto, Ontario (Dr Miller); Department of Epidemiology and Health Promotion, National Public Health Institute, Helsinki, Finland (Dr Pietinen); Department of Epidemiology and Population Health, Albert Einstein College of Medicine, Bronx, NY (Dr Rohan); Division of Nutritional Epidemiology, The National Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden (Dr Wolk); and Department of Environmental Medicine, New York University, New York (Dr Zeleniuch-Jacquotte). Dr Park is now with the Nutritional Epidemiology Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Department of Health and Human Services, Bethesda, Md.

JAMA. 2005;294(22):2849-2857. doi:10.1001/jama.294.22.2849
Abstract

Context 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.

Design, Setting, and Participants 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.

Main Outcome Measure 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.

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