The colon is the lower part of the intestinal tract. It extends from the caecum to the rectum. In the colon, water and salts are absorbed from undigested foods, and muscles move the waste products towards the rectum.
The colon contains a vast population of many types of bacteria, which have potentially important functions. These include the fermentation of unabsorbed carbohydrate (non-starch polysaccharides and resistant starch) to release energy and short-chain fatty acids that influence the health of the colonic mucosa. The colon is lined with mucous membranes and contains lymphoid cells that form part of the body’s immune defences.
Incidence and survival rates
Colorectal (bowel) cancer is the third most common cancer worldwide. About 1.4 million new cases of colorectal cancer were recorded globally in 2012, accounting for 10 per cent of all new cases of cancer.
Colorectal cancer is the fourth most common cause of death from cancer, estimated to be responsible for almost 700,000 cancer deaths. Colorectal cancer survival depends on the stage at which it is diagnosed, with later-stage diagnosis having poorer survival. The five-year survival rate is 90 per cent for colorectal cancers diagnosed at an early stage compared with 13 per cent for those diagnosed at a late stage.
The highest estimated rates are in Australia and New Zealand, and the lowest in Western Africa. Patterns of colorectal cancer cases in men and women are similar globally.
Over the next 15 years, the number of cases of colorectal cancer is expected to increase by 60 per cent to more than 2.2 million. Globally it is one of the cancers whose incidence is increasing.
Lifestyle factors and colorectal cancer risk
In this report from our Continuous Update Project (CUP) – the world’s largest source of scientific research on cancer prevention and survivorship through diet, nutrition and physical activity – we analyse global research on how certain lifestyle factors affect the risk of developing colorectal cancer. This webpage forms part of the World Cancer Research Fund/American Institute for Cancer Research Third Expert Report Diet, Nutrition, Physical Activity and Cancer: a Global Perspective.
Findings on colorectal cancer
There is strong evidence that:
- being physically active DECREASES the risk of colon cancer
- consuming wholegrains DECREASES the risk of colorectal cancer
- consuming foods containing dietary fibre DECREASES the risk of colorectal cancer
- consuming dairy products DECREASES the risk of colorectal cancer
- taking calcium supplements DECREASES the risk of colorectal cancer
- consuming red meat INCREASES the risk of colorectal cancer
- consuming processed meat INCREASES the risk of colorectal cancer
- consuming alcoholic drinks INCREASES the risk of colorectal cancer
- being overweight or obese INCREASES the risk of colorectal cancer
- being tall INCREASES the risk of colorectal cancer
There is some evidence that:
- consuming foods containing vitamin C might decrease the risk of colon cancer
- consuming fish might decrease the risk of colorectal cancer
- vitamin D might decrease the risk of colorectal cancer
- consuming multivitamin supplements might decrease the risk of colorectal cancer
- low consumption of non-starchy vegetables might increase the risk of colorectal cancer
- low consumption of fruit might increase the risk of colorectal cancer
- consumption of foods containing haem iron might increase the risk of colorectal cancer
Other causes of colorectal cancer
In addition to the findings on diet, nutrition and physical activity outlined above, other established causes of colorectal cancer include:
Smoking 40 cigarettes (two packs) per day increases risk of colorectal cancer by about 40 per cent and nearly doubles the risk of colorectal cancer death.
- other diseases
Inflammatory bowel disease (Crohn’s disease and ulcerative colitis) increases the risk of colon cancer.
Long-term use (five years or more) of at least 75 mg per day of the non-steroidal antiinflammatory drug aspirin can reduce the risk of colorectal cancer. Hormone therapy in postmenopausal women decreases colorectal cancer risk.
Approximately 95 per cent of colorectal cancers are adenocarcinomas. Other types of cancer that can occur include mucinous carcinomas and adenosquamous carcinomas.
Carcinogens can interact directly with the cells that line the colon and rectum. Between five and 10 per cent of colorectal cancers are a consequence of recognised hereditary conditions. The two major ones are familial adenomatous polyposis (FAP) and hereditary non-polyposis colorectal cancer (HNPCC). A further 20 per cent of cases occur in people who have a family history of colorectal cancer. People with FAP have a mutation in the tumour-suppressor gene APC which regulates cell growth and develop a large number of adenomas at a relatively young age; if left untreated, nearly all will develop colorectal cancer by the time they reach age 40. On average, people develop HNPCC in their mid-40s; having this form of the disease also increases the risk of a number of other gastrointestinal cancers. HNPCC involves mutations in DNA repair genes.
These two conditions also lead to sporadic colorectal cancer. The so-called ‘gatekeeper’ pathway involves the disruption of genes that regulate growth – principally APC, as in FAP – and is involved in 85 per cent of sporadic colorectal cancers. The ‘caretaker’ pathway, which is characterised by disruption to genes that maintain genetic stability as in HNPCC, leads to 15 per cent of sporadic cancers.
Full references and a summary of the mechanisms underpinning all the findings can be found in the colorectal cancer report.
How the research was conducted
The global scientific research on diet, nutrition, physical activity and the risk of colorectal cancer was systematically gathered and analysed, and then independently assessed by a panel of leading international scientists in order to draw conclusions about which of these factors increase or decrease the risk of developing colorectal cancer.
Published findings in peer-reviewed journals
Selected findings from this report have been published in peer-reviewed journals. Details of the papers and links to the abstract in PubMed are below:
Height and body fatness and colorectal cancer risk: an update of the WCRF-AICR systematic review of published prospective studies. Abar, Vieira AR, Aune, Sobiecki JG, Vingeliene S, Polemiti E, Stevens C, Greenwood DC, Chan DSM, Schlesinger S, Norat T. Eur J Nutr. 2017 Oct 28. doi: 10.1007/s00394-017-1557-1. Abstract
Adult weight gain and colorectal adenomas-a systematic review and meta-analysis. Schlesinger S, Aleksandrova K, Abar L, Vieira AR, Vingeliene S, Polemiti E, Stevens CAT, Greenwood DC, Chan DSM, Aune D & Norat T. Ann Oncol 2017 Jun 1;28(6):1217-1229. doi: 10.1093/annonc/mdx080. Abstract
Foods and beverages and colorectal cancer risk: a systematic review and meta-analysis of cohort studies, an update of the evidence of the WCRF-AICR Continuous Update Project. Vieira AR, Abar L, Chan DSM, Vingeliene S, Polemiti E, Stevens C, Greenwood D, Norat T. Ann Oncol. 2017 Aug 1;28(8):1788-1802. Abstract
Red and processed meat intake and risk of colorectal adenomas: a systematic review and meta-analysis of epidemiological studies. Aune D, Chan DS, Vieira AR, Navarro Rosenblatt DA, R Vieira, Greenwood DC, Kampman E & Norat T. Cancer Causes Control. 2013; 24 (4): 611-27. Abstract
Carbohydrates, glycemic index, glycemic load, and colorectal cancer risk: a systematic review and meta-analysis of cohort studies. Aune D, Chan DS, Lau R, Vieira R, Greenwood DC, Kampman E & Norat T. Cancer Causes Control. 2012; 23 (4): 521-535. Abstract
Recent Evidence for Colorectal Cancer Prevention Through Healthy Food, Nutrition, and Physical Activity: Implications for Recommendations. Perera PS, Thompson RL & Wiseman MJ. Curr Nutr Rep. 2012 DOI 10.1007/s13668-011-0006-7 Abstract
Dairy products and colorectal cancer risk: a systematic review and meta-analysis of cohort studies. Aune D, Lau R, Chan DS, Vieira R, Greenwood DC, Kampman E & Norat T. Ann Oncol. 2012 (1); 23: 37-45. Abstract
Nonlinear reduction in risk for colorectal cancer by fruit and vegetable intake based on meta-analysis of prospective studies. Hurst R, Hooper L, Norat T, Lau R, Aune D, Greenwood DC, Vieira R, Collings R, Harvey LJ, Sterne JA, Beynon R, Savovic J & Fairweather-Tait SJ. Am J Clin Nutr. 2012; 96(1): 111-22. Abstract
Red and processed meat and colorectal cancer incidence: meta-analysis of prospective studies. Chan DS, Lau R, Aune D, Vieira R, Greenwood DC, Kampman E & Norat T. PLoS ONE. 2011; 6: e20456. Abstract
Dietary fibre, whole grains, and risk of colorectal cancer: systematic review and dose-response meta-analysis of prospective cohort studies. Aune D, Chan DSM, Lau R, Vieira R, Greenwood DC, Kampman E & Norat T. BMJ 2011; 343:d6617 Nov 10. Abstract
Meta-analyses of vitamin D intake, 25-hydroxyvitamin D status, vitamin D receptor polymorphisms and colorectal cancer risk. Touvier M, Chan DS, Lau R, Aune D, Vieira R, Greenwood DC, Kampman E, Riboli E, Hercberg S & Norat T. Cancer Epidemiol Biomarkers Prev. 2011; 20: 1003-16. Abstract
This webpage is a summary.
For much more, download the full chapter.