Home | Irritable Bowel Syndrome (IBS)

What is Irritable Bowel Syndrome (IBS)?

IBS affects more than 1 in 10 adults in Australia. IBS is a disorder of gut-brain interaction (DGBI) or ‘functional’ gut condition that is characterised by:

  • gut pain at least one day a week for at least three months (and at least six months since it first started) AND
  • changed stool (poo) form (ranging from diarrhoea to constipation or alternating between the two) or frequency.
  • related symptoms (that are not part of diagnosis) can include wind and bloating.


If you experience gut pain or symptoms that do not involve altered bowel habits, then it is not classified as IBS but could be another functional gut condition such as functional dyspepsia.

What causes IBS?

IBS is caused by sensitivity of the gut-brain axis. This sensitivity could be due to genetics, altered gut bacteria, a bout of ‘gastro’ or parasite infection. The gut becomes very sensitive to increased pressure caused by gas or fluid. Certain foods or stress can trigger symptoms if the brain over-reacts to messages sent from the digestive tract. This can happen before it is even possible for foods to have moved to the lower gut, showing how powerful the gut-brain (or brain-gut) response can be. If you suspect that you have IBS, speak to your doctor about your symptoms and history.


More about IBS diagnosis

IBS can be tricky to diagnose because it relates to the functioning of the digestive system, not gut structure. IBS cannot be diagnosed via blood tests or exploratory investigations. Often people with gastro-intestinal symptoms will have had some investigations to see if there is anything structurally causing their gut symptoms, and if these are all clear, then the symptoms and absence of any other condition result in a diagnosis of IBS. Breath tests can be used to find out if lactose, fructose, sorbitol and mannitol malabsorption might be triggering IBS symptoms. These should be completed and interpreted by a medical doctor and are not diagnostic for IBS.


More about IBS subtypes and symptoms

There are several types of IBS – diarrhoea (IBS-D) and constipation (IBS-C) types. Some unfortunate people have both (it’s called IBS mixed or IBS-M). The feelings associated with diarrhoea could include gut pain, cramping, urgent need to use the toilet, lack of control over the bowels or even lack of sensation that the bowels are opening. Constipation symptoms could include pressure, pain and bloating in the lower gut.

Anyone can suffer the symptoms of IBS sometimes to some degree. For example, don’t we all get gassy after eating baked beans or get a bit bloated after too much bread? This is because we humans don’t fully digest some sugars and fibres. The gases produced by bacteria when they break down those sugars and fibres cause symptoms in people with IBS. Some sugars also draw extra fluid into the gut, causing diarrhoea and abdominal pain in people who have a sensitive gut.


What are the risk factors?

Factors that might contribute to IBS include:

  • Stress
  • Poor dietary habits – especially a low fibre intake
  • Antibiotics causing gut bacteria dysbiosis
  • Hereditary factors
  • More women are diagnosed with IBS than men, but this could relate to reporting.


Interesting but painful irritable bowel facts

  • 10% of GP visits relate to IBS.
  • Between 20% and 50% of gastroenterologist visits relate to IBS.
  • IBS is the 2nd most common cause of missed work days.
  • People with IBS have 50% higher medical costs than the general population.
  • IBS impairs quality of life – sufferers would trade up to 15 life years for a cure to their IBS.
  • The usual age of diagnosis of IBS is between 30 and 50 years (although many have symptoms for a long time before diagnosis).

Dietary management of IBS

Our dietitians work with you to work out what food components or lifestyle triggers set off your symptoms and navigate your path to managing IBS with you. Our expertise extends to dietary management of ‘tricky’ or overlapping conditions, such as a combination of IBS/IBD or functional dyspepsia/coeliac disease.


A short-term low FODMAP diet followed by food challenges is one approach to finding out which foods trigger IBS symptoms (or not), but it’s not the only approach and it does not work for everyone. A low FODMAP diet involves removing high FODMAP foods from your diet for about a month to relieve your symptoms. Your dietitian then supports you to test how you respond to CHALLENGE foods from each F-O-D-M-A-P category, before gradually re-introducing these foods until you achieve a good balance between diet variety and symptom relief.


The low FODMAP diet has an overall success rate of about 70% for people with IBS. Some people who don’t get symptom relief from dietary approaches respond well to gut-brain IBS management. We provide guidance on how to integrate these therapies alongside diet for holistic management, tailored to match your food preferences and lifestyle, while avoiding symptom triggers.


Drs Kerith Duncanson and Georgina Williams have completed extensive research in IBS and gut related topics.