The exact cause of bowel cancer is still unknown. However, research has shown several factors may make you more likely to develop it.
Cancer occurs when the cells in a certain area of your body divide and multiply too rapidly. This produces a lump of tissue known as a tumour.
Most cases of bowel cancer first develop inside clumps of cells called polyps on the inner lining of the bowel.
However, it doesn't necessarily mean you'll get bowel cancer if you develop polyps.
Some polyps regress, and some don't change. Only a few grow and eventually develop into bowel cancer over a period of several years.
The main risk factors for bowel cancer are outlined below.
Around 1 in 20 people develop bowel cancer. Almost 18 out of 20 cases of bowel cancer in the UK are diagnosed in people over the age of 60.
Having a family history of bowel cancer in a first-degree relative – a mother, father, brother or sister – under the age of 50 can increase your lifetime risk of developing the condition yourself.
If you're particularly concerned that your family's medical history may mean you're at an increased risk of developing bowel cancer, it may help to speak to your GP.
If necessary, your GP can refer you to a genetics specialist, who can offer more advice about your level of risk and recommend any necessary tests to periodically check for the condition.
A large body of evidence suggests a diet high in red and processed meat can increase your risk of developing bowel cancer.
For this reason, the Department of Health advises people who eat more than 90g (cooked weight) a day of red and processed meat cut down to 70g a day.
Read more about red meat and bowel cancer risk.
There's also evidence that suggests a diet high in fibre could help reduce your bowel cancer risk.
Read more about eating good food and a healthy diet.
People who smoke cigarettes are more likely to develop bowel cancer, as well as other types of cancer and other serious conditions, such as heart disease.
Read more about stopping smoking.
Drinking alcohol has been shown to be associated with an increased risk of bowel cancer, particularly if you regularly drink large amounts.
Read about drinking and alcohol for more information and tips on cutting down.
Being overweight or obese is linked to an increased risk of bowel cancer, particularly in men.
If you're overweight or obese, losing weight may help lower your chances of developing the condition.
People who are physically inactive have a higher risk of developing bowel cancer.
You can help reduce your risk of bowel and other cancers by being physically active every day.
Read more about health and fitness.
Some conditions affecting the bowel may put you at a higher risk of developing bowel cancer.
For example, bowel cancer is more common in people who have had extensive Crohn's disease or ulcerative colitis for more than 10 years.
If you have one of these conditions, you'll usually have regular check-ups to look for signs of bowel cancer from about 10 years after your symptoms first develop.
Check-ups involve examining your bowel with a colonoscope – a long, narrow flexible tube that contains a small camera. This is inserted into your bottom.
The frequency of the colonoscopy examinations will increase the longer you live with the condition. This also depends on factors such as how severe your ulcerative colitis is and whether you have a family history of bowel cancer.
There are two rare inherited conditions that can lead to bowel cancer:
- familial adenomatous polyposis (FAP) – a condition that triggers the growth of non-cancerous polyps inside the bowel
- hereditary non-polyposis colorectal cancer (HNPCC), also known as Lynch syndrome – an inherited gene fault (mutation) that increases your bowel cancer risk
Although the polyps caused by FAP are non-cancerous, there's a high risk that over time at least one will turn cancerous. Most people with FAP have bowel cancer by the time they're 50.
As people with FAP have such a high risk of getting bowel cancer, they're often advised by their doctor to have their large bowel removed before they reach the age of 25.
Families affected can find support and advice from FAP registries such as The Polyposis Registry provided by St Mark's Hospital, London.
Removing the bowel as a precautionary measure is also usually recommended in people with HNPCC as the risk of developing bowel cancer is so high.
Want to know more?