What are the risk factors for bowel cancer?

A risk factor is any factor that is associated with increasing someone’s chances of developing a certain condition, such as cancer. Some risk factors are modifiable, such as lifestyle or environmental risk factors. Others cannot be modified, such as inherited factors or whether someone in the family has had cancer.

Having one or more risk factors does not mean you will develop cancer. Many people have at least one risk factor but will never develop cancer, while others with cancer may have had no known risk factors. Even if a person with cancer has a risk factor, it is usually hard to know how much that risk factor contributed to the development of their disease.

Bowel cancer risk factors

Both men and women are at risk of developing bowel cancer. The risk is greater if you:^1,2,3

are aged 50 years or over – your risk increases with age
have had an inflammatory bowel disease, such as Crohn’s disease or ulcerative colitis
have previously had special types of polyps, called adenomas, in the bowel
have previously had any type of bowel cancer
have a significant family history of bowel cancer or adenomatous polyps.

Other risk factors include:^1,2,4

excess body fat and physical inactivity
high intake of particular foods (such as red and processed meats)
a low blood level of vitamin D
high alcohol consumption; even low alcohol consumption may be associated with some risk of developing bowel cancer
smoking
some gene mutations
type 2 diabetes.

Anyone, including younger people, with concerns about their risk of developing bowel cancer should talk to their doctor.

Healthy lifestyle and risk reduction

The following modifiable lifestyle factors can reduce your risk of developing bowel cancer.^5,6,7

Not smoking

Cancer Australia recommends not smoking and avoiding exposure to second-hand smoke to reduce cancer risk.

Controlling overweight and obesity

Cancer Australia recommends achieving and maintaining a healthy body weight within a BMI (body mass index) range of 18.5–25 kg/m² to reduce cancer risk, and a waist circumference below 94 cm for men and below 80 cm for women.

Undertaking physical activity

Cancer Australia recommends aiming for at least 30 minutes of moderate-intensity physical activity every day and limiting sedentary habits, such as watching television, to reduce cancer risk.

Having a healthy diet

Cancer Australia recommends consuming adequate dietary fibre, including unprocessed cereals (grains) and pulses (legumes), and aiming for 5 servings of vegetables and 2 servings of fruit per day. Cancer Australia recommends limiting intake of red meat to less than 500 g per week and avoiding processed meat to reduce cancer risk. Cancer Australia recommends limiting intake of salt and processed foods with added salt to reduce cancer risk.

Limiting alcohol consumption

The lifetime risk of harm from drinking alcohol increases with the amount consumed.⁹ For healthy men and women, drinking no more than 2 standard drinks on any day reduces the lifetime risk of harm from alcohol-related disease or injury.

On the basis of international evidence specific to cancer,¹ it is recommended that, if alcoholic drinks are consumed, women further limit alcohol consumption to 1 standard drink, to reduce cancer risk.