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Causes and risk factors of colon cancer

In the UK, about 31,000 people develop colon cancer each year. The exact cause of colon cancer is unknown. However, things called risk factors can increase the chance of a person developing it. Having one or more risk factors does not mean you will definitely develop colon cancer. Equally, if you do not have any risk factors, it doesn’t mean you won’t get colon cancer.


Like most types of cancer, colon cancer is more common in older people. In the UK, almost 6 in 10 bowel cancer cases (58%) each year are diagnosed in people aged 70 and over.


Eating a lot of red and processed meat increases the risk of colon 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 colon cancer and eating poultry, such as chicken and turkey.

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

Physical activity

People who are not physically active are more likely to develop colon cancer.

Body weight

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


Colon 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 colon cancer. People with these conditions may be offered regular bowel screening with a test called a colonoscopy.

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

Family history

Most people who get bowel cancer do not have a family history of it. Having one relative who developed bowel cancer at an older age does not significantly affect your risk.

If several close family members on the same side of your family have had bowel cancer, this may increase your risk. You may also have a higher risk if a close family member developed bowel cancer before the age of 50. 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). For more information, contact your GP or call our cancer support specialists on 0808 808 00 00.

We have more information about having a family history of bowel cancer and bowel screening.

Inherited (familial) conditions

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

There are two rare conditions that can run in families:

People with either condition have a very high risk of developing bowel cancer.

We have information about cancer genetics.

Colon cancer is not infectious and can’t be passed on to other people.

Back to Diagnosing

How colon cancer is diagnosed

You might notice changes in your body. There are lots of possible causes for different symptoms, so it’s important to know what to look out for. If your doctor wants to find out more they might organise different tests or scans.