How IBS Works


Irritable Bowel Syndrome, AKA IBS, is a functional bowel disorder affecting up to 20% of the population worldwide. You’re most certainly not alone if you have IBS!

IBS sufferers show no signs of physical damage to the structure of their bowel, which is why it is referred to as a functional condition – the problem lies with how the large intestine operates, as opposed to there being the presence of an organic disease that can be validated through clinical tests.

As a result, irritable bowel syndrome often goes undiagnosed for many years leaving sufferers feeling frustrated at their impaired quality of life and dissatisfied with the level of support they have received from their doctor throughout their journey.

It doesn’t have to be this way though! Armed with the information on this page, you’ll be informed and empowered to push for a diagnosis and learn what you can do to get some relief from your symptoms.


Common symptoms of IBS include:

– A change in bowel habit (diarrhoea, constipation or both)
– Lower abdominal pain and cramping
– Bloating (an uncomfortable feeling of fullness)
– Excessive gas (farting a lot)
– Distension (a visible increase in the size of your tummy)

Symptoms can come and go (relapse and remit), and may ‘flare up’ for a period then disappear for weeks or months before returning. Symptom severity can also increase and decrease, ranging from mild to severe.

The predominant bowel habit you have will classify your IBS into one of four subtypes which can be useful in guiding your options for targeted therapies. The four subtypes are:

– IBS-D (diarrhoea predominant)
– IBS-C (constipation predominant)
– IBS-M (alternating diarrhoea and constipation)
– IBS-U (unable to classify)

Other symptoms may be present depending on your subtype (for example, a sensation of incomplete pooping in IBS-C and mucus in your poop if you have IBS-D).


There are various symptoms of IBS that overlap with organic diseases such as inflammatory bowel disease (IBD), intestinal cancers and coeliac disease.

The following red flag symptoms are not typical symptoms of IBS and need to be investigated by your doctor ASAP:

– Unexplained weight loss
– Fever
– Bleeding when you go to the toilet
– Recurrent vomiting
– Persistent daily diarrhoea
– Waking at night to empty your bowels
– Symptoms that progressively get worse

If you are over 50 years old when your symptoms begin, or if you have a family history of bowel disorders other than IBS, it’s also a good idea to see your doctor to rule out anything more sinister.

How IBS Is Caused


Unfortunately, the exact cause of IBS is not known, but there is strong evidence to suggest that is it multifactorial, meaning there are several possible causes behind the condition. These include:

Altered Motility
Gut motility is the speed at which food moves through your digestive tract. If motility is accelerated, or too quick, this can lead to diarrhoea. If motility is delayed, or too slow, this can result in constipation.

Enhanced Gut-Brain Interactions
The ‘gut-brain axis’ is a bidirectional (two-way) reflex circuit that handles communication between the gut and the brain. Stress and anxiety can influence motility, affect pain threshold and impair the function of the mucosal barrier in the large intestine.

Altered Gut Microbiota
The ecosystem of microbes that live deep inside our bowel are different in IBS sufferers when compared to healthy controls. At the moment, we don’t know if this difference is a cause or consequence of IBS, but one of the jobs these microbes has is to ferment certain types of carbohydrates called FODMAPs, and in doing so, they produce gas which can cause pain and discomfort.

Check out the below video for a detailed explanation on how this works.

IBS appears to have a hereditary component, as having a mother or father with IBS is a predictor of the condition. However, environmental exposures and learned behaviours may account for this increased risk, rather than a true genetic predisposition.

Previous Gastrointestinal (GI) Infection
Bacterial gastroenteritis can cause post-infectious IBS in a small subgroup of people. Symptoms usually come on suddenly following a GI infection and may be prompted by the release of a toxin that alters bowel function by the bacteria that caused the infection. Other possible causes of post-infectious IBS include low-grade inflammation and damage to the nerves lining the gut that control motility and pain awareness.

Other Possible Causes
Intestinal permeability, low-grade inflammation and immune system activation have been postulated as other potential causes of IBS but more research is needed to confirm whether these factors are indeed at play or not.

Getting to the root cause of IBS is not straight forward, which can make getting relief tricky if you don’t have the correct support from an IBS specialist who can guide you through evidence-based strategies to manage your symptoms.


Currently, there are no tests to accurately confirm IBS so diagnosis is made using the Rome IV criteria to assess your symptoms.

This should be done by a doctor (no, Doctor Google doesn’t count!) and some investigations may be necessary to rule out other conditions such as coeliac disease, endometriosis and IBD.

These tests are very straight forward and can be carried out by your GP – there’s usually no need for a referral to a specialist gastroenterologist.

Tests your doctor may order:

– Full blood count
– C-reactive protein
– Nutritional markers
– Coeliac screening
– Fecal calprotectin

Endoscopies and colonoscopies are not generally required to diagnose IBS. Excessive tests and procedures are considered counterproductive, and just delay getting a diagnosis.

Can IBS Be Cured


The short answer to this is no; sadly, there is no cure for IBS.

However, it’s not all doom and gloom. There are many ways you can effectively manage your IBS symptoms so you can get your life back.

There are a number of known food and drink gut irritants, and you may have a FODMAP sensitivity, but randomly cutting out foods from your diet will do your gut more damage in the long run. When it comes to identifying food triggers, the gold standard is an elimination diet, which should be guided by a trained IBS expert (like me!). This is especially important if you eat a plant-based diet, to make sure nutritional deficiencies are avoided.

IBS management requires a holistic approach. Although we often (understandably) blame the food we eat for triggering symptoms, dietary changes are only one strategy in the toolkit to IBS freedom. Sleep, stress, and movement are all critical for the long-term relief of irritable bowel syndrome.

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