[4 min read] Irritable Bowel Syndrome & the low FODMAP diet

Did you know that 1 in 7 people are affected by Irritable Bowel Syndrome (IBS)? IBS is a functional disorder with severity that often changes over time– it doesn’t cause lasting damage nor contribute to the development of serious bowel conditions, such as cancer or colitis. Various management strategies exist for IBS, including prescribed and over-the-counter medications, and drug-free approaches involving medical nutrition therapy (4).

For further information on this topic, you may be interested to learn more about the HealthCert Professional Diploma program in Medical Nutrition Management.

The causes of IBS are unclear, but many people find it presents after an episode of gastroenteritis, food poisoning, infection, illness, or chronic stress (1). People with IBS tend to present with a collection of unpredictable and often embarrassing symptoms which may significantly impact their quality of life, including diarrhoea (sometimes referred to as IBS-D); constipation – (sometimes referred to as IBS-C); excessive wind; bloating/distension; cramps, and fatigue (2, 3). These symptoms are also common in other bowel conditions, and it is important that primary care physicians rule out other conditions before IBS can be diagnosed in patients.

The low FODMAP diet

Developed by researchers at Monash University, the low FODMAP diet is now well recognised and noteworthy as an effective method to alleviate or manage IBS symptoms and improves symptoms in 3 out of 4 IBS sufferers (6).

The low FODMAP diet is an elimination style diet that works by restricting foods which are high in fermentable carbohydrates and then identifying which carbohydrate is causing symptoms (5). These fermentable carbohydrates are named FODMAPs (Fermentable Oligosaccharides, Monosaccharides, Disaccharides and Polyols). FODMAPs are poorly absorbed in the gastrointestinal system, and in people with IBS can result in triggering symptoms.

The diet is generally a three-step process best followed under the supervision of a qualified dietitian or experienced healthcare professional.

  • Phase 1, Elimination: This phase lasts 2-6 weeks. FODMAP foods are reduced to very small amounts so that the overall response to the restrictions can be assessed.
  • Phase 2, Reintroduction: This involves a series of food challenges to help identify trigger foods and amounts of foods tolerated.
  • Phase 3, Modified low FODMAP diet phase: Once the trigger FODMAPs and level of sensitivity are determined, patients can begin to reintroduce foods and FODMAPs that were tolerated well and avoiding only those that were problematic. This removes unnecessary restriction, which can limit foods high in prebiotics and plant variety.

The bottom line

IBS is a condition that negatively affects the digestive system and can cause unpleasant symptoms such as stomach cramps, bloating, and diarrhea. While medications can help, nutrition and lifestyle changes can also make a difference, and the low-FODMAP diet is recommended as first-line treatment. Because the diet can be challenging during the first, most restrictive phase, it’s important that patients work with a doctor to ensure they follow the diet correctly and maintain proper nutrition.

Learn more about medical nutrition for IBS with the online HealthCert Professional Diploma program in Medical Nutrition Management.

– Lynette Law, Accredited Practising Dietitian


  1. Lacy BE, Pimentel M, Brenner DM, Chey WD, Keefer LA, Long MD, et al. ACG Clinical Guideline: Management of Irritable Bowel Syndrome. Am J Gastroenterol. 2021;116(1):17-44.
  2. El-Serag HB, Pilgrim P, Schoenfeld P. Systemic review: Natural history of irritable bowel syndrome. Aliment Pharmacol Ther. 2004;19(8):861-70.
  3. Shorey S, Demutska A, Chan V, Siah KTH. Adults living with irritable bowel syndrome (IBS): A qualitative systematic review. J Psychosom Res. 2021;140:110289.
  4. Scaciota ACL, Matos D, Rosa MMB, Colovati MES, Bellotto E, Martimbianco ALC. INTERVENTIONS FOR THE TREATMENT OF IRRITABLE BOWEL SYNDROME: A REVIEW OF COCHRANE SYSTEMATIC REVIEWS. Arq Gastroenterol. 2021;58(1):120-6.
  5. Hill P, Muir JG, Gibson PR. Controversies and Recent Developments of the Low-FODMAP Diet. Gastroenterol Hepatol (N Y). 2017;13(1):36-45.
  6. Halmos EP, Power VA, Shepherd SJ, Gibson PR, Muir JG. A diet low in FODMAPs reduces symptoms of irritable bowel syndrome. Gastroenterology. 2014;146(1):67-75.e5.


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