Fiber Intake and Incidence of Colorectal Cancer among 76,947 Women and 47,279 Men
- Karin B. Michels1,2,3,
- Charles S. Fuchs3,5,
- Edward Giovannucci2,3,4,
- Graham A. Colditz2,3,
- David J. Hunter2,3,
- Meir J. Stampfer2,3,4 and
- Walter C. Willett2,3,4
- 1Obstetrics and Gynecology Epidemiology Center, Department of Obstetrics and Gynecology; 2Channing Laboratory, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School; Departments of 3Epidemiology and 4Nutrition, Harvard School of Public Health; and 5Department of Adult Oncology, Dana-Farber Cancer Institute, Boston, Massachusetts
- Requests for reprints
Karin B. Michels, Obstetrics and Gynecology Epidemiology Center, Brigham and Women's Hospital, Harvard Medical School, 221 Longwood Avenue, Boston, MA 02115. Phone: 617-732-8496; Fax: 617-732-4899. E-mail: kmichels{at}rics.bwh.harvard.edu
Abstract
Prospective cohort studies have consistently found no important link between fiber intake and risk of colorectal cancer. The recent large, prospective European Prospective Investigation into Cancer and Nutrition has challenged this paradigm by suggesting significant protection by high fiber intake. We prospectively investigated the association of fiber intake with the incidence of colon and rectal cancers in two large cohorts: the Nurses' Health Study (76,947 women) and the Health Professionals Follow-up Study (47,279 men). Diet was assessed repeatedly in 1984, 1986, 1990, and 1994 among women and in 1986, 1990, and 1994 among men. The incidence of cancer of the colon and rectum was ascertained up to the year 2000. Relative risk estimates were calculated using a Cox proportional hazards model simultaneously controlling for potential confounding variables. During follow-up including 1.8 million person-years and 1,596 cases of colorectal cancer, we found little association with fiber intake after controlling for confounding variables. The hazard ratio for a 5-g/d increase in fiber intake was 0.91 (95% confidence interval, 0.87-0.95) after adjusting for covariates used in the European Prospective Investigation into Cancer and Nutrition study and 0.99 (95% confidence interval, 0.95-1.04) after adjusting for additional confounding variables. Our data from two large prospective cohorts with long follow-up and repeated assessment of fiber intake and of a large number of potential confounding variables do not indicate an important association between fiber intake and colorectal cancer but reveal considerable confounding by other dietary and lifestyle factors.
Footnotes
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Grant Support: Department of Health and Human Services, National Cancer Institute, NIH grants CA87969 and CA55075 (Nurses' Health Study and Health Professionals' Follow-up Study) and Department of Health and Human Services, National Institute of Diabetes and Digestive and Kidney Diseases, NIH grant R01 DK54900 (K.B. Michels).
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The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
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- Accepted December 28, 2004.
- Received July 19, 2004.
- Revision received December 14, 2004.
