Despite bowel cancer being commonly diagnosed in Australia, it is potentially one of the most preventable cancers through the early detection of abnormalities from screening. The link between lifestyle factors, such as diet, and the risk of bowel cancer was first reposted by Denis Burkitt in the early 1970s. Dr Burkitt noticed a low incidence of gut diseases in native Africans, who consumed large intakes of dietary fibre, particularly resistant starch in the form of maize meals (Burkitt, 1971). In recent years, further studies have similarly suggested that individuals who consume more fibre-rich foods have reduced risks of colorectal/bowel cancers. In fact, the 2018 report by the World Cancer Research Fund concluded that there is strong evidence for a protective effect of foods containing dietary fibre against bowel cancer, and their Cancer Prevention Recommendations advise the consumption of >30g fibre per day (WCRF, 2018).
Dietary fibre is a type of indigestible carbohydrate that helps keep our digestive system healthy. Dietary fibre is mainly found in wholegrain cereals, fruits, vegetables and legumes. There are two key types of dietary fibre, the first being soluble fibre, which soaks up water like a sponge and helps to add bulk to stools. This fibre is great for slowing down the rate of digestion and also helps to reduce LDL or ‘bad’ cholesterol levels. Food sources of soluble fibre include fruit and vegetables, barley, flaxseed, psyllium husk and legumes. Alternatively, there is also insoluble fibre which is responsible for speeding up the time in which food passes through the gut and helps to soften stools, therefore supporting regular bowel movements and preventing constipation. Food sources of insoluble fibre include wholegrain breads and cereals, oats, nuts, seeds, and the skin from fruit and vegetables.
One of the main ways that dietary fibre can help reduce risk of bowel cancer is by limiting the exposure of the large bowel’s lining to harmful carcinogens. Dietary fibre is responsible for this in many ways, including binding carcinogens to stools, then expelling them from the body promptly.
Secondly, dietary fibre with prebiotic effects can also increase the amount and diversity of your gut bacteria. The beneficial gut bacteria convert fibre into short-chain fatty acids such as butyrate, which reduce the ability of cells in the intestine to become cancerous.
Finally, dietary fibre and butyrate also have anti-inflammatory properties. Inflammation can give rise to various diseases including bowel cancer, and people with inflammatory bowel diseases (IBDs) such as ulcerative colitis are at greater risk of developing bowel cancer.
Every day, men should be aiming for 30g of dietary fibre and women should be aiming for 25g.
Here are some tips to help boost your fibre intake throughout the day:
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