Posted: 11/28/2011; BMJ © 2011 BMJ Publishing Group
Colorectal cancer is the third most common type of cancer, with 1.2 million new cases diagnosed in 2008 worldwide, accounting for about 9.7% of all cases of cancer. Evidence from ecological studies, migrant studies, and secular trend studies suggest that environmental risk factors are of major importance in the cause of colorectal cancer. Dietary factors have been suspected as important, but only intakes of red and processed meat and alcohol are considered to be convincing dietary risk factors for colorectal cancer.
 
Conclusion: A high intake of dietary fiber, in particular cereal fiber and whole grains, was associated with a reduced risk of colorectal cancer. Further studies should report more detailed results, including those for subtypes of fiber and be stratified by other risk factors to rule out residual confounding. Further assessment of the impact of measurement errors on the risk estimates is also warranted.
Our meta-analysis supports an inverse association between intake of dietary fiber, cereal fiber, and whole grains and risk of colorectal cancer, but we found no significant evidence for an association with intake of fiber from fruit, vegetables, or legumes.