Can similar changes in the microbiome lead to both IBS and colon cancer?

I subscribe to ‘The Conversation’ and usually scan through its contents every morning.   This post by Bradley Meehan, PhD researcher in the Department of Molecular and Cellular Physiology, University of Liverpool caught my attention this weekend.  What you can do to reduce the risk of bowel cancer caused by e.coli?

For many years, it has been repeatedly stated by scientists that there is no increased risk of developing bowel cancer, no matter how many years you have IBS.   I have confidently repeated that to many patients even though experience has shown that IBS is an individual condition and there and nothing is absolute in medicine, only probabilities, and those depend on how you ask the question.

The connection between bacteria and infections was first publicised in the 19th century when Rudolf Virchow suggested that cancer may result from inflammation triggered by infections.  Soon after, the eminent bacteriologists of the day, Robert Koch and Louis Pasteur found bacteria in tumours.

Bacterial infections release molecules called cytokines,  which cause inflammation and marshal defence mechanisms that help to get rid of the infection.   This is fine in the short term, but if the bacterium persists, then chronic release of cytokines may contribute to cancer development.

Several bacteria have been linked to cancer via inflammation – Helicobacter pylori and stomach cancer, Salmonella typhi and gallbladder cancer, Streptococcus bovis and bowel cancer.

Trillions of bacteria live in your bowel,  hundreds of different species, which make up a biomass of 1-2 kg.  Bowel cancers are responsible for the fourth highest number of cancer-related deaths worldwide,  affecting up to 4% of people.  Yet only a small percentage of bowel cancers are linked to genetic risk. The majority of new cases occur somewhat randomly (sporadic cancers) or related to inflammatory bowel disease (IBD-associated cancers).

Most of the bacteria that live in your bowel are harmless.  They help to digest your food, produce vitamins and seal up leaks in the colonic wall.   But some bacteria are harmful. We are normally protected from harmful bacteria by our immune system and by other bacteria.

Certain lifestyle factors such as high-fat diets, alcohol consumption, smoking and stress alter the balance between the beneficial bacteria and the harmful bacteria.   The good bacteria struggle to survive, while some harmful, or “pathogenic”, bacteria thrive and multiply.  High numbers of pathogenic bacteria means higher risk of chronic inflammation and cancer.

Patients with inflammatory bowel disease and bowel cancers have been found with huge numbers of pathogenic E. coli living inside tumours. That’s because these E. coli can stick to and invade the cells lining our bowels and replicate themselves inside them. To make things worse, these E. coli are capable of producing a toxic substance called colibactin that damages the DNA of bowel cells making them cancerous.

Damage control

So what can you do to reduce the risk of inflammation and bowel cancer?

• Reduce your intake of fat and red meat
• Adopt a diet high in fibre and poorly absorbed starches and sugars. This will  encourages fermentation in the bowel and the growth of beneficial bacteria while reducing the impact of  pathogenic bacteria.  Part of the effect is related to the production of  butyrate. a product of carbohydrate fermentation, which nourishes the colonic cells and reduces inflammation.
• Eat bananas and broccoli, which contain poorly absorbed carbohydrates that can block harmful bacteria from sticking to your gut cells and promote their passage out of the gut. This is known as a contra-biotic effect and may in mediated by beneficial species of bacteria.
• Maintain adequate levels of Vitamin D with diet and exposure to sunlight. This has been shown to help kill pathogenic bacteria, particularly e.coli, even when they are already inside our cells. Vitamin D deficiency is also associated with colon cancer and has been implicated in IBS.  .
• Eat Almonds, red onions and chives.  These are high in molecules known as flavinoids that have antibacterial properties and could help limit the effects of pathogenic bacteria.
• Reduce you intake of alcohol and nicotine.
• Take regular exercise helps maintain a normal bacterial diversity in the gut and could reduce your risk of bowel cancer by up to 50%.
• Reduce stress with methods that enhance mindfulness 
• Take Anti-inflammatory drugssuch as aspirin have been shown to reduce the risk of bowel cancer and may work by reducing the inflammation caused by pathogenic bacteria.

All of these factors might be seen as components of what is generally regarded as a healthy diet and lifestyle. As Bradley Meehan commented ‘It is becoming more necessary for us to be proactive and increase our awareness of the impact we can have before cancers can even develop. In the coming years we are likely to see both drug-based and natural treatments that specifically target E. coli and other bacteria associated with inflammation and bowel cancer risk’.

Is this at all relevant to IBS?  Probably not.  Yet, diarrhoea predominant IBS is associated with activation of the immune system, low grade inflammation of the colon, alterations in gut permeability and increased bowel sensitivity.  It may be that the type of inflammation and the cytokines are different in IBS and cancer but some of the diet and life style factors proposed to reduce IBS may also reduce cancer risk.

Association, however, never implies causation, it just indicates questions that might be investigated.  One of these could be about the longer term impact of low fibre and low FODMAP diets in reducing the symptoms of IBS or increasing the risk of cancer. If restriction of poorly absorbed starches and sugars depletes beneficial bacteria and causes inflammation, then might the diets be producing a more sensitive gut while at the same time reducing the factors that trigger symptoms, a bit like needing to economise to afford an expensive life style.

So what is the answer?  As I have emphasised in recent posts, the low FODMAP diet has really helped some people to reduce the discomfort of their IBS.  However, if I were taking a low FODMAP diet, I would want to ensure I was taking adequate amounts of fibre and I had reintroduced all the FODMAP foods I could manage with reasonable comfort while addressing other psychological and life style factors that might be sensitising my gut.   .