Role of dietary factors in survival and mortality in colorectal cancer: a systematic review.

The role of dietary factors in the outcome of colorectal cancer (CRC) has been the subject of many studies, but results are inconclusive. Presented here are the results of a systematic review of studies published on dietary factors and CRC outcome in the English literature between March 2002 and March 2012. Studies were subdivided into survival studies in CRC patients and CRC mortality studies in the general population. Sixteen of the 636 studies identified - 5 on survival and 11 on mortality - met the predefined inclusion criteria. No consistent association between individual dietary components and CRC outcome was detected in the survival studies. In the mortality studies, an association between meat intake and increased CRC mortality was found in two ecologic studies; however, two prospective cohort studies did not confirm this association. An inverse association between cereal intake and CRC mortality was found in two ecologic studies. In conclusion, published studies investigating dietary factors and outcome in CRC are heterogeneous in design and findings. No dietary component was conclusively and consistently associated with survival in CRC patients. The results of mortality studies seem to indicate that meat intake has an adverse effect on CRC mortality, while cereal intake may be protective.