Doctor's Desk

Irritable Bowel Syndrome (IBS)

is a gastrointestinal disorder of gut-brain interaction characterized by recurrent abdominal pain associated with altered bowel habit in the absence of organic disease.


While the exact pathophysiology of IBS remains unknown, it has been proposed that disturbances in the intestinal nerves that affect motility and perception of intestinal stretching may result in symptoms. 

Causes of these disturbances may depend on the interaction of several factors including genetics, psychosocial factors, and post-inflammatory changes after a gastrointestinal infection.

Physical stress and infections, such as gastroenteritis, have been shown to be likely to precede IBS diagnoses; however, psychological factors (e.g. anxiety, depression) and life stressors (e.g. divorce, family illness, financial difficulties etc.) can also play a role.

IBS Pathophysiology 

Diagnosis of IBS

IBS is diagnosed by a doctor, after the exclusion of other conditions and cause of symptoms. 

Diagnosis of IBS is symptom-based using the Rome IV criteria.

ROME IV Criteria

Recurrent abdominal pain on average at least one day a week in the last three months associated with two or more of the following:

  • related to defecation

  • associated with a change in a frequency of stool

  • associated with a change in form (consistency) of stool.

Symptoms must have started at least six months ago.

Doctor and Patient
Halved Avocado

Dietary management of IBS

Diet plays a key role in the management of IBS. Some interventions that may be considered in the management of IBS can include:

  • Change in dietary habits

  • Modified fibre diet

  • Prebiotics 

  • Probiotics 

  • Digestive enzymes 

  • Elimination Diet (Low FODMAP diet) 

Healthy Food

The Low FODMAP Diet 

The low FODMAP diet is an evidence based dietary strategy to successfully manage IBS. FODMAP is an acronym for Fermentable Oligo-, Di, Mono-saccharides And Polyols. It is considered to be a second-line dietary strategy after assessment and management of dietary and lifestyle factors that may contribute to symptoms. 

The low FODMAP diet involves collective restriction of a group of short-chain carbohydrates that have been shown to  increase small intestinal water volume and be rapidly fermented in the large intestine, leading to increased gas (e.g. hydrogen) production and gastrointestinal symptoms (i.e. pain, bloating, distension, flatulence, nausea and altered bowel motility).

The low FODMAPs diet is a dietitian-taught program to ensure nutritional intake adequacy despite food restrictions. The long-term restriction of FODMAPs is not recommended. Structured reintroduction of  FODMAPs is recommended after two to six weeks to identify which FODMAPs you are sensitive to, your level of tolerance to each individual high FODMAP foods, and optimise food variety and self-management long term.

  1. Gastrointestinal System - Irritable Bowel Syndrome Background. 2018. PEN

  2. Drossman DA, Hasler WL. Rome IV-Functional GI Disorders: Disorders of gut-brain interaction. Gastroenterology. 2016 May;150(6):1257-61. doi: 10.1053/j.gastro.2016.03.035. Citation available from:

  3. National Institute for Health and Clinical Excellence. Irritable bowel syndrome in adults. Diagnosis and management of irritable bowel syndrome in primary care. London (UK): National Institute for Health and Clinical Excellence. Clinical guideline 61 Update 2015. Available from:


Ongoing symptoms? other considerations

  • Food chemical sensitivities  (RPAH Elimination Diet)

  • Sucrase-isomaltase deficiency or Disaccharidase deficiency

  • Bile acid malabsorption

  • SIBO

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