The epidemiologic evidence and potential biological mechanisms for a protective effect of dietary fiber on the risk of colorectal cancer

Cancers of the colon and rectum represent a significant cause of morbidity and mortality worldwide with the burden especially high in North America, Europe, and in some parts of Asia. More than half of the disease burden has been attributed to an inappropriate diet and lifestyle. Low intakes of dietary fiber are considered to be a risk factor for colorectal cancer, although the epidemiological evidence until now has been conflicting in part due to the difficulties in reliably examining the relationships between components of the diet and disease outcomes due to bias, confounding, and measurement error. Results from recently published, large, prospective, cohort studies and from a meta-analysis of the evidence provide "convincing" evidence of an independent dose-response relationship between total dietary fiber intake and increasing risk of colorectal cancer. The anticarcinogenic properties of fiber on cancers of the colon and rectum, however, have still to be elucidated.