Causes of bowel cancer

A 'risk factor' is something that increases your chances of getting a disease. Sometimes this risk comes from something you do (for example not getting enough exercise, eating a poor diet, having a high alcohol intake or smoking) and sometimes there is nothing you can do about the risk (for example your age or family history).

Risk factors for bowel cancer that you can change

Smoking

Long-term smokers are more likely than non-smokers to develop bowel cancer. If you smoke, quitting will have many health benefits, including reducing your risk of getting bowel cancer.

Inactive lifestyle

Lack of physical exercise has now been identified as the single most important risk factor for developing bowel cancer. Try to do at least half an hour of moderate physical activity five times a week, so that you get comfortably out of breath. The more active you are, the more you cut your risk of bowel cancer

Alcohol intake 

Bowel cancer has been linked to a heavy intake of alcohol (regularly drinking more than 4 units of alcohol a day for men).  Alcohol intake in moderation appears to be associated with a much lower risk e.g. 1 small drink a day for women or 2 small drinks a day for men. The more you cut down, the more you reduce your risk.

Diet 

The incidence of bowel cancer in the 'developing' world is still generally low and experts believe that diet is a major contributory factor. The following dietary factors appear to increase the risk of bowel cancer:

• A diet high in processed foods containing saturated fats and sugar, and regular, excessive calorie intake
• A diet containing large amounts of red and processed meat
• A low intake of dietary fibre from whole grains, fruit and vegetables and not drinking enough water.   

Obesity

Obesity and Body Mass Index ratios of 40 or more are strongly associated with an increased risk of bowel cancer. It is therefore very important to find a balance between diet and exercise that allows you to maintain a healthy weight and significantly reduce your risk of developing all cancers, including bowel cancer.

Risk factors for bowel cancer that you cannot change

Below are risk factors which you cannot change. This does not, however, mean that you will get bowel cancer but that you have an increased chance of developing bowel cancer.

Bowel diseases

If you have had polyps (non-cancerous, but abnormal tissue in your bowel) or other chronic inflammatory bowel problems (including Crohn's disease and ulcerative colitis) you may have a higher risk of developing bowel cancer than people who do not have these conditions.

Family history and genetics

Bowel cancer can “run in the family” and people who have a close member of their family with bowel cancer have an increased likelihood of developing bowel cancer themselves. A smaller number of cases are due to inherited, genetic reasons.

Age

Whilst bowel cancer is increasing in the younger age groups, 8 out of 10 people (83%) who develop bowel cancer are age 60 and over.