Gut health tips to lower the risk of bowel cancer

Who can develop bowel cancer?

Both men and women can develop bowel cancer. Bowel cancer was historically considered to be a disease that predominantly affected older adults. However, we have seen an increasing incidence of bowel cancer amongst young adults less than 50 years old worldwide over the past two decades. The rates of colon cancer in older adults over the age of 65 have decreased since the 1990s, which may be due to improvements in screening or related to altered lifestyle factors. Young adults with bowel cancer are often diagnosed at a more advanced stage than older adults, which may be attributed to a delay in diagnosis. It is, therefore, imperative that bowel cancer is detected in the early stages to improve treatment outcomes.

Risk factors for developing bowel cancer

The risk of developing bowel cancer depends on many factors, including:

• Age: Although incidence rates are increasing amongst younger adults, it still remains most prevalent in older adults.
• Family history: Individuals with a first-degree relative with colon cancer may be up to four times more likely to develop bowel cancer.
• Genetics: Genetic conditions such as familial adenomatous polyposis (FAP) or Lynch syndrome are associated with an increased risk of developing bowel cancer.
• Bowel inflammation: Long term inflammatory bowel conditions such as ulcerative colitis and Crohn’s disease may increase the risk of developing bowel cancer.
• Diet and lifestyle factors: A systematic review published in 2021 identified the following potential risk factors for early-onset colorectal cancer; processed meats, sugary drinks, excessive alcohol intake, physical inactivity, and smoking.
• Gut microbiome: The gut microbiota may play a role in the risk of developing bowel cancer. There have been some animal studies looking at the impact of the gut microbiome composition on cancer risk, however further studies in humans are needed to draw conclusions. Some evidence has shown that individuals with diagnosed colon cancer have an altered gut microbiome compared to healthy controls.

Prolonged antibiotic exposure; especially during childhood, can negatively influence gut microbiome composition and therefore overuse may be linked to an increased risk of developing colon cancer. However, this correlation has not been proven as a ‘cause and effect’ and antibiotics should still be taken if they are indicated for certain illnesses.

Red flag symptoms to look out for

Speak to your GP if you experience any of the following symptoms;

• Bleeding from your back passage or blood in your stools.
• A change in your regular bowel habits, such as looser or more frequent stools or constipation lasting longer than three months.
• Persistent abdominal pain or pain in your rectum.
• Unintentional weight loss
• Unexplained anaemia, which may be associated with symptoms of tiredness or breathlessness.

Screening for bowel cancer

Screening for bowel cancer is really important to improve treatment outcomes. More than 90% of bowel cancer cases diagnosed in the early stages are treated successfully.

To rule out suspected bowel cancer, a GP or Gastroenterologist can complete a stool test to check for traces of blood in the stools. This is also known as a FIT (Faecal Immunochemical Test). A blood test can also be completed to check blood cells and haemoglobin levels.

If bowel cancer is suspected, further investigations may be considered such as a camera test to look at the bowel i.e. colonoscopy, flexible sigmoidoscopy or a colon capsule endoscopy.

See Cancer Research UK website for more details.

How can you reduce your risk of bowel cancer?

Although the risk of developing bowel cancer is often multifactorial, addressing diet and lifestyle factors may help to reduce your risk. As the gut microbiome is thought to play a role in developing bowel cancer, focusing on looking after your gut health would be beneficial.

1. Include a variety of foods

Aiming to include 30 different plants per week will help to optimise gut microbiome diversity and nourish your beneficial gut microbes. Think about including the super six: wholegrains, fruit, vegetables, beans, pulses, nuts and seeds. Including prebiotic fibre, otherwise known as fuel for the beneficial gut bacteria, can increase the production of short-chain fatty acids (SCFAs) in the colon. SCFAs such as butyrate may help to reduce the risk of tumour growth in the bowel.

2. Focus on colour 

Polyphenols are plant chemicals responsible for plants’ various coloured pigments. They have an antioxidant effect on the body, helping to fight off harmful free radicals and protect against the risk of developing cancer.

3. Increase your overall fibre intake

Eating a minimum of 30g of fibre per day can help to decrease your risk of developing bowel cancer. The average fibre intake in the UK is approximately 18g per day. Data from the American Institute for Cancer Research has shown that for every 10g increase in overall daily fibre intake, there is a 7% reduction in bowel cancer risk. There is some evidence that individuals with a higher intake of fibre from wholegrains had a lower risk of bowel cancer.

4. Stay physically active

Some evidence suggests that people who are more physically active, regardless of body weight, are less likely to develop bowel cancer. Focus on staying physically active and moving your body in ways you enjoy.

5. Limit your intake of red meat and ultra-processed foods

A prospective study from 2020 showed that individuals consuming an average of 76g/day of red and processed meat compared to 21g/day had a 20% higher risk of bowel cancer. Limit your intake of red meat to less than 350g (cooked weight) per week and limit ultra-processed red meats such as sausages, bacon and salami. High intakes may negatively alter the gut microbiome composition, and some preservatives in processed meats, such as nitrates, may increase the risk of developing bowel cancer. Char-grilling meats at high temperatures can generate carcinogens, which may increase bowel cancer risk.

6. Reduce alcohol intake

Alcohol consumption has been linked to the development of early-onset bowel cancer and hefty alcohol intake. A prospective study from 2020 indicated an 8% increased risk of bowel cancer for every 10g/day alcohol intake. Minimise your intake of alcohol, keeping within the government-recommended guideline of less than 14 units per week.

7. Avoid smoking

Evidence has shown that smoking cigarettes increases the risk of bowel cancer, with an increased risk associated with the number of cigarettes smoked daily. 7% of bowel cancers in the UK are associated with smoking cigarettes. Quitting smoking can reduce bowel cancer risk.