The exact cause of bowel cancer is still unknown. However, research has shown several factors may make you more likely to develop it.
How does it develop?
Cancer happens when the cells in an 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. These are on the inner lining of the bowel. It doesn't always mean you will get bowel cancer if you develop polyps.
Some polyps regress, and some don't change. Only a few grow and develop into bowel cancer over a period of several years.
What are the risk factors?
The 9 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 Ireland are diagnosed in people over the age of 60.
2. Family history
Having a history of bowel cancer in a first-degree relative under 50 can increase your risk of developing the condition. A first-degree relative is a mother, father, brother or sister.
You should talk to your GP if you're concerned that your family's medical history may mean you are at a higher risk. If necessary, your GP can refer you to a genetics specialist. They can offer more advice about your level of risk and recommend any necessary tests to check for the condition.
A diet high in red and processed meat can increase your risk of developing bowel cancer.
Drinking alcohol has been shown to be linked with an increased risk of bowel cancer - especially if you drink large amounts, often.
Being overweight or obese is linked to a higher risk of bowel cancer, especially in men.
People who are physically inactive have a higher risk of getting bowel cancer.
8. Digestive disorders
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 will usually have regular check-ups to look for signs of bowel cancer from about 10 years after your symptoms first develop.
9. Genetic conditions
There are two rare inherited conditions that can lead to bowel cancer:
- Familial adenomatous polyposis (FAP)
This is a condition that triggers the growth of non-cancerous polyps inside the bowel. Polyps caused by FAP are non-cancerous, but there is a high risk that over time at least one will turn cancerous. People with FAP have a high risk of getting bowel cancer and are often advised by their doctor to have their large bowel removed before the age of 25.
- Hereditary non-polyposis colorectal cancer (HNPCC)
Also known as Lynch syndrome, this is an inherited gene fault that increases your bowel cancer risk. Removing the bowel as a precautionary measure is usually recommended for people with HNPCC, as the risk of developing bowel cancer is so high.
How can I reduce my risk?
The most important things you can do to reduce your risk of bowel cancer are:
- Take part in the national BowelScreen screening programme
- Keep a healthy weight for your height – if you are overweight or obese, losing weight may help lower your chances of getting cancer
- Eat a balanced diet. Avoid processed meats, red meat and fatty foods. Eat more fibre, fruit and vegetables
- Stop smoking and stay within the low-risk limits for alcohol
- Stay active. You can help reduce your risk of bowel and other cancers by being active every day