Eating to reduce risk of bowel cancer

June is Bowel Cancer Awareness Month, a time to raise awareness of the second deadliest cancer in Australia that takes about 80 lives per week.

The focus of Bowel Cancer Awareness Week is early detection- as the earlier the disease is detected, the better the long-term outcome. Sitting alongside the need for early detection of bowel cancer (also known as colorectal cancer) is the need to reduce the overall lifetime risk of developing this cancer, which can affect young people as well as older people.

Last year the World Cancer Research Fund [1] examined the results of 99 studies from around the world, comprising more than 29 million adults and over 247,000 cases of bowel cancer. The subsequent report showed that there is strong evidence to show that

  • consuming foods that contain dietary fibre decreases the risk of colorectal cancer

  • consuming dairy products decreases the risk of colorectal cancer

  • consuming wholegrains decreases the risk of colorectal cancer

Yes, it’s all pointing back to the same message again- eat a healthy and balanced diet (sound familiar??), but what I really want to focus on in this blog is the importance of retaining grains and dairy in the diet.

I see many people on social media and in 'real-life' removing grains and/or dairy from their diet in order to lose weight or because they think eating gluten-free or dairy-free will help them to ‘feel better’. In doing so, they are unwittingly missing out on the cancer-decreasing benefits of including these foods in their diet. Yes, they are often including lots of fruit and vegetables in their diets, but evidence shows that the fibre from wholegrains is more protective for bowel cancer than the fibre from fruits and vegetables. Why is this so?

Grains, and wholegrains in particular, have been singled out in the research as particularly protective against the development of bowel cancer. There are two biological explanations for this- the first is that the type of fibre in wholegrains (insoluble fibre) helps to bulk up your stools and move them along the intestines more quickly, keeping us regular rather than constipated. The waste products in our stools may contain carcinogens so getting these out of the body more quickly is of benefit. The other reason is that wholegrains don’t tend to be broken down until they reach the end of the intestines (ie. the colon and rectum), and when they are broken down there a gas called butyrate is produced which may inhibit the growth of tumours in the colon and rectum[2]. These protective effects of wholegrains make them an important part of the diet, and removing them for a short-term weight loss etc may have long-term health implications.

The calcium that is so readily available in dairy foods is thought to have a protective effect on the development of colorectal cancer due to its ability to bind to substances that may be toxic to the colorectum (unconjugated bile acids and free fatty acids). In addition, both the protein component of the milk (casein) and the carbohydrate component (lactose) are thought to increase the ability of the body to absorb the calcium in the dairy products, meaning more calcium is available to bind these toxic substances. As with wholegrains, removal of dairy foods from the diet can also mean the removal of the protective effect of calcium for bowel cancer development (not to mention the increased risk of osteoporosis).

Ensuring that you get a good supply of fibre, particularly that from wholegrains, and calcium will help to reduce your overall lifetime risk of bowel cancer, so eat up! If you've been avoiding grains and/or dairy from your diet due to an allergy or intolerance, seek the advice of an Accredited Practising Dietitian who can help you work out what foods may be a suitable substitute (eg. lactose free milk, gluten free breads etc). And remember that this is about reducing risk- not eliminating risk. So if you notice any changes in your bowel habits, blood when you go to the toilet, or any frequent pain from gas or abdominal cramps go and see your GP.

[1]World Cancer Research Fund International/American Institute for Cancer Research. Continuous Update Project Report: Diet, Nutrition, Physical Activity and Colorectal Cancer. 2017. Available at:

[2]Avivi-Green C, Polak-Charcon S, Madar Z, et al. Apoptosis cascade proteins are regulated in vivo by high intracolonic butyrate concentration: correlation with colon cancer inhibition. Oncol Res. 2000;12:83-95

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