Can fibre lower your risk of developing bowel cancer?

What is bowel cancer?

Bowel cancer (also known as colon/colorectal cancer) is a type of cancer that originates within the large intestine (colon) or rectum. Cancer Research UK reports that bowel cancer is the 4th most common cancer in the UK with over 44,000 new cases are diagnosed each year (1). More than 9 out of 10 people who develop bowel cancer in the UK are over the age of 50 although younger adults are increasingly being diagnosed. 

Bowel cancer risk factors

The risk of developing bowel cancer can depend on multiple things (2), including: 

• Age - most prevalent in older adults  

• Family history and genetics – your risk may be increased if you have a family history of the disease, particularly if it is a first degree relative. Diseases such as Lynch syndrome and familial adenomatous polyposis can also increase the risk. 

• Bowel inflammation – long term inflammation such as ulcerative colitis and Crohn’s disease may increase the risk. 

• Diet and lifestyle – consumption of processed meat, sugary drinks, excess alcohol intake, and smoking are all shown to increase risk (3). 

What’s the connection with fibre? 

Fibre is a type of carbohydrate that naturally occurs in plant foods including wholegrains, fruit, vegetables, legumes, nuts and seeds. Fibre is well known for its role in aiding digestion, promoting regular bowel movements, and preventing constipation (3). Prebiotic fibre helps your gut microbiome thrive via the production of short chain fatty acids (SCFAs). SCFA have known links to supporting cognitive function, energy levels, and can help strengthen your immune system (4). But did you know that a higher intake of fibre has been linked to a reduced risk of bowel cancer? 

According to Cancer Research UK, over half of all bowel cancer cases could be prevented through lifestyle changes (5). One change that research has shown to be particularly effective is increasing intake of dietary fibre.

Firstly, fibre adds bulk to the stool and speeds up bowel transit time. Studies have shown that this can reduce the amount of time that carcinogens (such as nitrates and nitrites that are found in processed meat) are in contact with the colon lining, reducing their ability to cause cancer (6).

Prebiotic fibre is fermented by the gut bacteria to produce SCFAs. Studies have shown that these SCFAs have a huge role in preventing the development of bowel cancer; they act on epithelial cells that line the colon as well as regulate the body’s immune T cells (7). 

Research has also found that a lower fibre diet typically coincides with a diet that is high in processed and red meat which are known to increase the risk of developing bowel cancer (8).

So, how can I increase my fibre intake? 

The UK government guidelines recommend that we consume around 30g of fibre a day (9), however most adults in the UK are only consuming an average of 20g a day. It is important that we consume enough fibre daily as the American Institute for Cancer Research has shown that a 7% reduction in bowel cancer risk is found for every 10g of daily fibre intake (10). In addition to this, not only is fibre important to lower the risk of bowel cancer, but it’s also associated with a lower risk of heart disease, type 2 diabetes, and stroke. 

Fibre is found in plant-based foods such as: 

• Wholegrains - wholegrain bread, quinoa, brown rice, wholegrain pasta  

• A portion of wholegrain rice = 2.7g fibre 

• Legumes – lentils, chickpeas, beans 

• ½ can of baked beans = 9.8g fibre 

• Fruit – apple, pear, berries, bananas 

• Apple = 1.2g fibre 

• Vegetables – carrots, sprouts, broccoli 

• Skin on baked jacket potato = 4.7g fibre 

• Nuts and seeds – chia seeds, flaxseeds, almonds, walnuts 

• Small handful of nuts = 3.8g fibre 

Other lifestyle factors that impact bowel cancer risk 

Besides fibre intake, other lifestyle changes can reduce the risk of developing bowel cancer. The World Cancer Research Fund outlines the key diet and lifestyle factors that can affect the risk of developing bowel cancer (10): 

• Meat consumption 

• There is strong evidence that the consumption of processed meat is a convincing cause of increased bowel cancer risk, with red meat being a probable cause of increased risk. 

• Limiting intake or swapping these for plant-based alternatives has been shown to reduce the risk. 

• Quit smoking 

• There is an increased risk of bowel cancer in those who smoke. 

• Reduce or quit alcohol intake 

• There is strong, convincing evidence that consuming two or more alcoholic drinks per day increases the risk of bowel cancer. 

• Exercise 

• There is strong, convincing evidence that physical activity decreases the risk of bowel cancer. 

• This includes all types of activity: occupational, household, transport, and recreational. 

• It also improves digestion, supports healthy weight and lowers inflammation which are also linked to a reduced risk of developing bowel cancer. 

• Fat consumption 

• Experimental studies suggest that polyunsaturated fats (found in oily fish) have been shown to suppress the development of bowel cancer. 

• However, there is limited evidence to show if total fat consumption has an effect on bowel cancer risk. 

Take home message 

Although there are several factors that contribute to the development of bowel cancer, research suggests that a significant proportion of cases can be prevented. Although genetics and environment do play a role, there are dietary and lifestyle modifications that can help. Increasing your fibre intake will support your gut microbiome and reduce your risk of developing the disease. 

Additional resources 

The World Cancer Research Fund and the British Dietetic Association have some useful meal plans to help you reach 30g of fibre a day. 

• WCRF - https://www.wcrf.org/preventing-cancer/topics/fibre-wholegrains-and-cancer/ 

• BDA - https://www.bda.uk.com/resource/fibre.html 

References 

1. Cancer Research UK (2025). Bowel cancer statistics. [online] Cancer Research UK. Available at: https://www.cancerresearchuk.org/health-professional/cancer-statistics/statistics-by-cancer-type/bowel-cancer#BowelCS0.

2. World Cancer Research Fund (2025). Bowel cancer causes and risk factors . [online] World Cancer Research Fund. Available at: https://www.wcrf.org/preventing-cancer/cancer-types/bowel-cancer/bowel-cancer-causes-and-risk-factors/.

3. Puzzono, M., Mannucci, A., Grannò, S., Zuppardo, R.A., Galli, A., Danese, S. and Cavestro, G.M. (2021). The Role of Diet and Lifestyle in Early-Onset Colorectal Cancer: A Systematic Review. Cancers, [online] 13(23), p.5933. doi:https://doi.org/10.3390/cancers13235933.

4. Kim, C.H. (2023). Complex regulatory effects of gut microbial short-chain fatty acids on immune tolerance and autoimmunity. Cellular & Molecular Immunology, [online] 20(4), pp.341–350. doi:https://doi.org/10.1038/s41423-023-00987-1.

5. Cancer Research UK (2024). What is bowel cancer? | Cancer Research UK. [online] Cancerresearchuk.org. Available at: https://www.cancerresearchuk.org/about-cancer/bowel-cancer/about-bowel-cancer.

6. Kunzmann, A.T., Coleman, H.G., Huang, W.-Y., Kitahara, C.M., Cantwell, M.M. and Berndt, S.I. (2015). Dietary fiber intake and risk of colorectal cancer and incident and recurrent adenoma in the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial. The American Journal of Clinical Nutrition, [online] 102(4), pp.881–890. doi:https://doi.org/10.3945/ajcn.115.113282.

7. Liu, G., Tang, J., Zhou, J. and Dong, M. (2024). Short-chain fatty acids play a positive role in colorectal cancer. Discover Oncology, 15(1). doi:https://doi.org/10.1007/s12672-024-01313-5.

8. Rubin, K.H., Rasmussen, N.F., Petersen, I., Kopp, T.I., Stenager, E., Magyari, M., Hetland, M.L., Bygum, A., Glintborg, B. and Andersen, V. (2020). Intake of dietary fibre, red and processed meat and risk of late-onset Chronic Inflammatory Diseases: A prospective Danish study on the ‘diet, cancer and health’ cohort. International Journal of Medical Sciences, 17(16), pp.2487–2495. doi:https://doi.org/10.7150/ijms.49314.

9. NHS (2022). How to get more fibre into your diet. [online] NHS. Available at: https://www.nhs.uk/live-well/eat-well/digestive-health/how-to-get-more-fibre-into-your-diet/.

10. World Cancer Research Fund (2018). Diet, nutrition, physical activity, and colorectal cancer . [online] World Cancer Research Fund . Available at: https://www.wcrf.org/wp-content/uploads/2024/10/Colorectal-cancer-report.pdf.