Diet
Diet is an important factor and in particular eating too much red and processed meat and consuming high amounts of sugary drinks or highly refined processed carbs increases your risk.
It is estimated that around 13 out of 100 bowel cancer cases in the UK are linked to eating too much red and processed meat such as bacon, salami, sausages, canned meat or chicken nuggets, because they contain chemicals called nitrosamines.
The government recommends that people eating more than 90g of red and processed meat a day should reduce it to 70g or less.
It might help to swap red meat for chicken or fish. Eating more fibre also reduces your risk of bowel cancer. Eating too little fibre causes around 30 in 100 bowel cancer cases in the UK.
You can boost the fibre in your diet by eating more plant-based foods such as fruits, vegetables, pulses and wholegrains, swapping to brown rice, having low calorie popcorn instead of crisps and choosing wholegrain breakfast cereals.
Being overweight and obese
Obesity is a cause of bowel cancer. It is estimated that 11 out of 100 bowel cancers in the UK are linked to being overweight or obese.
Being overweight is having a BMI of between 25 and 30 and obese is having 30 or higher. Being physically active and eating a healthy, balanced diet is important. There is strong evidence which shows that people who are more physically active have a lower risk of bowel cancer.
A recent study found that being more active in the morning and evening could reduce the risk of colorectal cancer by 11% and suggested the timing of peak activity could play a “crucial role” in warding off the disease.
Smoking tobacco and drinking alcohol
Seven out of 100 bowel cancers in the UK are linked to smoking and it has been estimated that around six out of 100 bowel cancers in the UK are linked to drinking alcohol, in particular binge drinking.
Alcohol increases the risk of cancer because when it is metabolised, it breaks down into chemicals that can bind to DNA, resulting in mutations that could become cancerous.
Alcohol can also increase the levels of hormones linked to the development of some types of breast cancer. In general, the more alcoholic drinks a person consumes, the higher their risk of developing one of the associated cancers.
Family history
Your risk of bowel cancer is slightly increased if an immediate family member such as a parent, brother or sister, son or daughter has had the disease.
In 5-6% of cases there is a genetic predisposition and there are likely to have been other cases in the family. The risk is increased further if you have more than one relative diagnosed or you have a immediate family member diagnosed at a young age, for example, under the age of 45 years old.
There are also some rare inherited or genetic conditions that can increase your risk. The most common inherited conditions that cause bowel cancer are familial adenomatous polyposis (FAP) and Lynch syndrome. Specialists recommend that people with FAP have bowel surgery in their 20s. The surgeon usually removes the colon to prevent the development of bowel cancer.
Ulcerative colitis and Crohn’s disease
Ulcerative colitis and Crohn’s disease are chronic bowel diseases causing inflammation in the bowel. Having either of these diseases for many years increases your risk of bowel cancer.