Exercise in the prevention and treatment of colorectal neoplasms: effects and mechanisms
Objective. This review examines factors that influence the widely varying estimates of protection against colorectal adenomas and cancers associated with occupational and leisure activity, and it seeks a realistic value for use in the formulation of public policy. Attention is also directed to underlying mechanisms, and brief consideration is given to the merits of exercise programmes after the treatment of colorectal tumours.
Methods. The Ovid/Medline data base was searched systematically from January 1996 to November 2015. The terms exercise therapy, physical education/training, athletes, physical fitness and physical activity/motor activity together yielded 205,142 hits, and a combination of the terms colon cancer, rectal cancer, colon adenoma and colon diverticulitis identified 52, 622 unique articles. Combining the 2 searches with a restriction to human subjects identified 286 papers. A review of the abstracts to these articles yielded 3 papers on colorectal adenomas and physical activity, and 41 studies of leisure or occupational activity in relation to colorectal cancer. A further19 articles examined various aspects of the association between colorectal neoplasia and habitual physical activity. This data base was supplemented extensively by articles gleaned from PubMed, Google Scholar and personal files, with a particular emphasis upon occupational studies conducted prior to 1996.
Results. Almost all published research has found an association between physical activity and a reduced risk of colorectal adenomas. Risk ratios for sedentary behaviour have varied widely between studies, with a weighted average of 1.64 for 6 occupational studies, and 1.26 for 27 leisure studies; the relationship is apparently stronger in men than in women. A substantial association with a sedentary lifestyle has also been reported for colon cancers, with a weighted average risk ratio of 1.27 in 39 occupational studies, and of 1.59 in 46 leisure studies. Likewise, for rectal cancers, risk ratios average 1.17 in 27 occupational studies and 1.24 in 20 leisure studies. For both colon and rectal cancers, risk ratios associated with a lack of physical activity were at least as great in women as in men. Inter-study differences in the reported risk-ratios reflect, among other variables, sample size, age, sex and race of subjects, choice of covariates, and the method and timing of activity measurements. Underlying mechanisms of benefit probably vary with the pattern of exercise adopted, but may include a reduced formation of colorectal adenomas, increased colonic motility, increased prostaglandin secretion, an increased use of NSAIDs, dietary changes and avoidance of obesity, a reduced risk of diabetes mellitus and a healthy overall lifestyle. There is growing evidence that an active lifestyle also improves the immediate outcome of colorectal surgery, and that subsequent involvement in an exercise programme enhances functional capacity and quality of life, with a reduced risk of tumour recurrence.
Conclusions. There is now overwhelming evidence that vigorous habitual activity, either at work or in leisure, is associated with a reduced risk of adenomas and cancers of the colon and rectum. However, the reported benefits are based upon very high levels of weekly energy expenditure, and in terms of public policy the general sedentary population seems unlikely either to attain or to maintain such levels of effort; regular moderate physical activity seems unlikely to yield benefits >20% for colon tumours and >10% for rectal tumours.
Terms of Publication
Authors who publish with this journal agree to the following terms:
- Authors retain copyright and grant the Health & Fitness Journal of Canada’s right of first publication with the work simultaneously licensed under a Creative Commons Attribution License that allows others to share the work with an acknowledgement of the work's authorship and initial publication in this journal.
- Authors are able to enter into separate, additional contractual arrangements for the non-exclusive distribution of the journal's published version of the work (e.g., post it to an institutional repository or publish it in a book), with an acknowledgement of its initial publication in this journal.
- Authors are permitted and encouraged to post their work online (e.g., in institutional repositories or on their website) prior to and during the submission process, as it can lead to productive exchanges, as well as earlier and greater citation of published work (See The Effect of Open Access).
- The Contributor (author(s)) represents and guarantees that the Contributor is the sole proprietor of the work and the Contributor has full power to make this Agreement and grant that the work does not infringe the copyright or other proprietary right of any other person; and the work contains no libellous or other unlawful matter and makes no improper invasion of the privacy of any other person. The Contributor also represents and is responsible for the accuracy of the work.
- The Contributor will read, correct, and return promptly galleys and page proofs to the Editor (or designate). The Contributor will be responsible for the completeness and accuracy of these corrections. If the Contributor does not return galleys and page proofs within the schedule agreed upon with the Editor (or designate), the Publisher may proceed without the Contributor corrections.
- When applicable, the Contributor agrees to obtain written permissions and letters of agreement for all matter contained in the work that is protected by existing copyright, paying any permission fees for the use of text or illustrations controlled by others, and furnishing the Publisher with written evidence of the copyright owner’s authorization to use the material.
- When applicable, the Contributor agrees to obtain written permission for inclusion of any photographic materials involving a human subject, and provide the Publisher with written evidence of the subject’s authorization to use this material. In the case of subjects who have not reached the age of majority, the Contributor agrees to obtain and furnish the Publisher with written permission from the parent and/or legal guardian.
- The Contributor may draw on and refer to material in the work in preparing other articles for publication in scholarly and professional journals and papers for delivery at professional meetings, provided that credit is given to the work and to the Publisher.
- This agreement may not be changed unless the Contributor and the Publisher agree to the change by means of a formal addendum signed by the Contributor and the Publisher’s representative.
- This agreement shall be construed and governed according to the laws of the province of British Columbia and shall be binding upon the parties hereto, their heirs, successors, assigns, and personal representatives. Should any formal proceedings related to this agreement be brought, such formal proceeding may be brought only in the province of British Columbia.
By submitting an article to the Health & Fitness Journal of Canada the Contributor has accepted and agreed to all terms outlined in the copyright notice.