News | Feature

IBS and bowel cancer: are there any links?

27 Apr 2021

Professor Siwan Thomas-Gibson is a gastroenterologist and specialist who shares her expertise on bowel cancer, as well as diagnosis and management of gastroenterology conditions like IBS. 

April is both Irritable Bowel Syndrome (IBS) Awareness Month and Bowel Cancer Awareness Month. Professor Siwan Thomas-Gibson is a gastroenterologist and specialist endoscopist who specialises in the detection and prevention of bowel cancer, as well as diagnosis and management of gastroenterology conditions like IBS. She shares her expertise on these two, separate, conditions.

About Professor Siwan Thomas-Gibson

Professor Siwan Thomas-Gibson is a gastroenterologist and specialist endoscopist at St Mark’s National Bowel Hospital London. She is the Dean of St Mark’s Hospital Academic Institute and Professor of Practice in Gastrointestinal Endoscopy at Imperial College London.

Broadly speaking, what is IBS and the range of symptoms?

IBS is a very common condition. More than 70% of people will experience symptoms of IBS at some point in their life. Broadly speaking it is to do with longstanding symptoms associated with your guts (stomach or bowels) including constipation, or diarrhoea, abdominal pain or indigestion. The hallmark feature is that they are long-standing, taking place over several months, or even years.

However, importantly, IBS does not have any ‘alarm features’ such as bleeding, weight-loss or a lump in the belly. 

How is IBS diagnosed?

IBS is almost a diagnosis of exclusion. When there is a pattern of key features such as the symptoms mentioned above, particularly over a long period of time, this is a sign the patient may be suffering from IBS.

Equally, by excluding factors such as blood in the stool, anaemia, a lump or a mass in the stomach, then we can be reassured that there is nothing else going on. To provide a clinical diagnosis we take a medical history, including a family history, and examine the patient to exclude other conditions, before diagnosing IBS. 

Is IBS relative to age group/lifestyle? 

IBS can affect people of any age starting from teenage years. It’s less likely to present for the first time in older age groups. Therefore, if a patient presents with symptoms at an older age, and if it isn’t a condition they have suffered with previously, then we would be inclined to investigate further.

There are lifestyle factors such as diet because the bugs that live in our gut interact with the food we eat and can cause symptoms. Smoking, alcohol consumption and obesity are detrimental; also lack of sleep, stress and anxiety all have an impact on the gut. 

What are the current forms of prevention and treatment?

Until recently we have been treating the symptoms. If people had diarrhoea we would give them anti-diahroaeals; if people were constipated we would give them laxatives; if people were in pain we would give them pain-killers. 

However, one of the big advances in IBS management is the discovery of a wide range of foods called FODMAPS, which can interact with the healthy bugs in our gut and cause symptoms.

a FODMAP list amongst different types of food

The foods that react with me will be different to the foods that react with you, and that’s because I’ve got different bugs in my gut to the ones that you have.

The range of foods may include things like apples, pears, onions, garlic, beans and lentils, but also some surprising ones such as gluten in bread and pasta, and even for some people milk and other lactose products. 

Trying to work out which of these foods is a trigger for you can be quite difficult. However, once you do identify a pattern and recognise the association you may be able to reduce the amount of that food that you have and thereby lesson the symptoms.

Some patients may have a lot of triggers though, in which case it’s best for them to see a dietician. Certainly, if you try to avoid all FODMAP foods you would have a very limited diet, so to do a true low FODMAP diet you really need to be under the guidance of an expert dietician. 

If pain is a significant symptom we can use Nortriptyline, which interrupts the nerve pathways between the brain and the gut. It used to be prescribed as an anti-depressant, but we are using it as a pain-killer and it has been found to be very effective.

If people are suffering from diarrhoea or constipation, we can prescribe anti-diarrhoeals or laxatives, respectively.

We have to find our own way to manage stress be that through sport, meditation, yoga, a good night’s sleep, or spending a relaxing time with friends or family.

It will be a different solution for different people, but it’s important to find the best way to manage this. When we are stressed, and even when we’re excited, the brain is interacting with the gut and this can cause problems. 

Hypnotherapy and behavioural therapies have also proven to be effective. When stress is having a significant impact upon a patient, a cycle of worrying about their symptoms can exacerbate the symptoms further.

IBS can of course co-exist with other medical conditions as well, which may also be causing stress. Psychological therapies can be a good way to reduce stress and therefore reduce the symptoms. 

The other treatment that is thought to be of help for IBS is pro-biotics, although there is little scientific evidence of this and as a food supplement, it isn’t something that can be prescribed. Patients can of course buy it for themselves, though as IBS is a very individual condition, it may work for some but not for others. 

As well as being IBS awareness month this is also bowel cancer awareness month - are the two related? 

No, IBS does not lead to bowel cancer. The only way IBS and bowel cancer are related is that they can both cause bowel symptoms. People who have had IBS for quite some time may not recognise the change in symptoms, which could be a sign of bowel cancer.

It’s really important for everybody, whether you have a diagnosis of IBS or not, to consult your doctor if you have a change in longstanding bowel symptoms. Alternatively, your doctor may recommend a more specialised test such as a colonoscopy or CT scan.

When should someone feel it's necessary to investigate symptoms which may be related to bowel cancer?

If you develop bleeding or a change in your symptoms and bowel movements, if you feel a lump in your stomach, or sudden weight loss (without dieting) or fatigue for example. These are symptoms which may be caused by bowel cancer. However, sometimes there are not any symptoms at all, which is why bowel screening is so important. 

What are the treatment options for bowel cancer?

Prevention is key and I would encourage people to take a bowel cancer screening test. This may be as simple as a stool test which picks up traces of blood in your stool. Even if it is positive this doesn’t necessarily mean you have cancer.

Of all those with blood in their stool it’s likely to be 3 - 5 out of 100 who might have bowel cancer. But they might have a polyp and by removing that we can prevent them from getting cancer, or they might just have haemorrhoids, but better to know.

Alternatively, your doctor may recommend a more specialised test such as a colonoscopy or CT scan.

There are very good survivor rates for bowel cancer and the number of people dying is falling. We are diagnosing more and more at an earlier stage, and if you can do this the survivorship rate is excellent.

People can follow the healthy lifestyle advice but also don’t be embarrassed about going to the doctors.

We have got to get over the embarrassment about bowel symptoms, because if you avoid talking about your symptoms you miss out on something that could be easily treated – and that could be life-saving. Don’t die of embarrassment!

Finally, think of your gut as an engine and the food we put in there is the fuel. The higher class the fuel, the longer your engine will work!

Further information

Digestive health services


Bowel cancer treatment



Any views expressed in this article are those of the featured specialist(s) and should not be considered to be the views or official policy of The London Clinic.