Age, lifestyle, diet and other conditions

In the UK, about 14,000 people develop rectal cancer each year.

The exact cause of bowel cancer is unknown. But certain things called risk factors can increase the chances of developing it.

Having one or more risk factors doesn't mean you will definitely get cancer. Equally, if you don’t have any risk factors, it doesn't mean you won’t get bowel cancer.

Age

Like most types of cancer, bowel cancers are more common in older people. More than 80% of bowel cancers (8 in 10) are diagnosed in people over 60.

Diet

A diet containing a lot of red and processed meat increases the risk of bowel cancer. Red meat includes beef, lamb and pork. Processed meat includes smoked meat, ham, bacon, sausages, pâté and tinned meat. Eating fried or grilled meat may also increase the risk.

Eating two or more portions of red or processed meat a day seems to increase the risk the most. People who eat less than two portions a week have the lowest risk.

No link has been found between bowel cancer and eating poultry (such as turkey and chicken).

Not eating enough fruit and fresh vegetables may also increase risk.

Physical inactivity

People who aren’t physically active are more likely to develop bowel cancer.

Body weight

Being overweight can increase the risk of developing bowel cancer, especially in men.

Smoking

Bowel cancer is more common in people who have smoked cigarettes for many years.

Inflammatory bowel conditions

Having an inflammatory bowel condition such as ulcerative colitis or Crohn’s disease can increase the risk of bowel cancer. People with these conditions may be offered regular bowel screening with colonoscopies.

Irritable bowel syndrome is not an inflammatory bowel condition and does not increase the risk of developing bowel cancer.

Family history

Most people who get bowel cancer don’t have a family history of it. Having one relative who developed bowel cancer at an older age doesn’t significantly affect your risk. But, if several close family members on the same side of your family have had bowel cancer, or if a close family member developed bowel cancer before the age of 50, this may mean you have a higher risk. Close family members are parents, brothers and sisters.

People who have a history of bowel cancer in their family can be referred to a specialist clinic to have their risk assessed. People at high risk of bowel cancer are offered bowel screening. This involves regular tests to look at the inside of the large bowel (colonoscopy).

Inherited genes

About 5% of bowel cancers (5 in every 100) are caused by an inherited faulty gene.

There are two rare conditions that can run in families: familial adenomatous polyposis (FAP) and Lynch syndrome (also called hereditary non-polyposis colorectal cancer or HNPCC). People with either condition have a very high risk of developing bowel cancer.

We have more information about inherited genes and bowel cancer.