In the UK, approximately 36,000 people each year develop cancer of the colon. The cause of cancer of the large bowel in most people is still unknown, but research is going on all the time to try to find the cause. Like most types of cancer, bowel cancer is more common in older people. It is unusual for people under 50 to get bowel cancer.
Research suggests that bowel cancer may be linked to diet. It is thought that a diet high in animal fat and protein, and low in fibre (fruit and vegetables), may increase the risk of developing cancer of the bowel. People who drink alcohol heavily may be at higher risk of bowel cancer.
Inherited faulty genes
A person who has one or more family members with bowel cancer may have a higher risk of developing it. They are usually only at higher risk if bowel cancer has been diagnosed in a close family member (such as a parent, sister or brother) under the age of 45 years, or when there is bowel cancer in several close members of the same family.
People who are worried about bowel cancer because of their family history can be referred to specialist clinics. At the clinic their risk will be carefully assessed. Regular screening, usually with a colonoscopy, can be arranged for people who have a high risk of developing the disease. Contact your GP or our cancer information and support service for more information. You can also read our section, Are You Worried About Bowel Cancer?
There are two rare genetic conditions in which people have a high risk of developing bowel cancer. In Familial Adenomatous Polyposis (FAP), many benign tumours called polyps are found in the lining of the colon. People with FAP have a high risk of developing bowel cancer. In another inherited genetic condition known as Hereditary Non-Polyposis Colon Cancer (HNPCC), bowel cancers develop at an early age, sometimes in more than one place in the bowel.
Only about 5% (5 in every 100) of bowel cancers are caused by an inherited faulty gene.
People who have had ulcerative colitis or Crohn’s disease for a long time also have an increased risk of developing bowel cancer. Ulcerative colitis and Crohn’s disease are diseases of the lining of the bowel.
Other factors that may increase the risk of bowel cancer include being overweight, taking very little exercise and smoking.