Colorectal cancer (CRC) is the second most common cancer (excluding non-melanoma skin cancer) in the US and the fourth most common cause of death from cancer worldwide. Epidemiological studies suggest that environmental factors contribute to the aetiology of colorectal cancer. Burkitt proposed an association between high fibre intake and colorectal cancer (CRC) based on the low age-adjusted rates of CRC reported in various rural regions in Africa. 1 Due to the observations that rural Africans

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... ) eat a diet rich in fibre from unrefined grains and/or leafy vegetables and (2) defecate stools that are bulkier, softer and less odorous than the stools of Westerners, he proposed a protective effect of fibre on CRC. Several epidemiological studies, especially ecologic and casecontrol studies, have shown an inverse association between dietary fibre and colorectal cancer. However, recent prospective studies like the Nurse's Health Study 2 and a study of a Swedish mammography-screening cohort 3 reported no relation between fibre intake and colon cancer incidence. Furthermore, increased dietary fibre intake did not reduce colorectal adenoma recurrence in three recent clinical trials. [4] [5] [6] We evaluated the association between total dietary fibre intake and incident CRC in a cohort of 45 491 women that had previously participated in the Breast Cancer Detection Demonstration Project (BCDDP). We also analysed the data for associations between source of fibre (fruits, vegetables, beans, grains) and cancer by location (colon, rectum, descending and sigmoid colon, and caecum and ascending colon). Conclusions Within a cohort of older women characterized by a relatively low fibre intake, there was little evidence that dietary fibre intake lowers the risk of colorectal cancer. • Increased dietary fibre intake might lower the risk for colorectal cancer. • There was no evidence in our cohort of older women with overall low fibre intake that dietary fibre lowers the risk for colorectal cancer. of previous and proposed methods. Epidemiol Rev 1992;14:177-96. 15 Panel on the definition of dietary fibre, Food and Nutrition Board, Institute of Medicine. Dietary Reference Intakes Proposed Definition of Dietary Fibre. National Academy Press, 2001. 16 Slavin JL, Martini MC, Jacobs DR Jr, Marquart L. Plausible mechanisms for the protectiveness of whole grains. Am J Clin Nutr 1999;70(3Suppl.):459S-63S. 17 Schatzkin A. Going against the grain? Current status of the dietary fibre-colorectal cancer hypothesis. Figure 1 Relative risks (95% CI) comparing highest with lowest intakes of dietary fibre in nested case-control and prospective cohort studies. Produced using results from references 14-21