The low FODMAP diet is recommended to control the symptoms caused by Irritable Bowel Syndrome (IBS) such as, bloating, abdominal pain, excessive wind, diarrhoea and/or constipation.

What is the low FODMAP diet you say?

It is a restrictive diet that eliminates specific sugars that are poorly absorbed and rapidly fermented in the gut. These sugars are known as Fermentable Oligosaccharides, Disaccharides, Monosaccharides And Polyols (hence the name FODMAPs). As gut bacteria start fermenting these FODMAP molecules, people can experience a range of symptoms including bloating, abdominal pain, excessive wind, diarrhoea and/or constipation.

The low FODMAP diet should be implemented under the guidance of a dietitian, and only after seeking medical advice from your doctor or gastroenterologist. This is an important step as your medical specialist will likely want to test for a range of other diseases and conditions that can cause similar symptoms as IBS, such as inflammatory bowel disease and coeliac disease. 

Your dietitian will guide you through the three stages of the low FODMAP diet:

  1. Elimination or “low FODMAP” phase
  2. Re-challenge phase
  3. Adapted low FODMAP diet

The elimination phase in which you restrict FODMAPs from your diet should be implemented for anywhere between 2-6 weeks. But no longer. This phase aims to bring your symptoms under control.

“So, if my IBS symptoms have improved then why can’t I stay on the Elimination phase forever?”

The aim of the re-challenge (second) phase is to determine two things: which FODMAP sugars are the cause of your symptoms; and the amount of FODMAP sugars you are able to tolerate whilst still maintaining symptom control.  So let’s circle back to the question “can’t I stay on the Elimination phase forever?”. No, it is not advised for the following reasons:


The low FODMAP diet is very restrictive and often removes many well-loved foods. It can impact on qualify of life and social eating, which can be psychologically and emotionally damaging.  In addition, the risk of nutrient deficiencies can increase following unnecessary long-term food restriction.  These most commonly include calcium, iron and fibre.


The aim of the re-challenge phase is to enable the expansion and liberalisation of your diet.  Remaining on the elimination phase of the low FODMAP diet becomes socially difficult, inconvenient, and importantly takes the fun out of eating! Ultimately, the goal is to be able to enjoy meal times, the foods you love, be confident in social situations, all whilst managing your IBS symptoms.


Some FODMAPS are also prebiotic fibres. So, a strict low FODMAP diet is also going to be low in the intake of these prebiotic fibres.  This is a concern long term, as healthy bacteria that live within our large intestine actually use these prebiotic fibres as a food source to survive.  The reduction in prebiotic intake on a low FODMAP diet may negatively alter the gut microbiota in as little as 3-4 weeks.  This may have effects on long-term health. 


So, if you have been following the low FODMAP diet and feel your symptoms are under control, this my friends is a sign you are ready to commence the second phase – the rechallenge phase – of the low FODMAP diet. If you are unsure or anxious about fully committing and understanding how to transition into this stage, then please get in touch with your dietitian.

Don’t have a dietitian on board? Book an appointment with one of our dietitians at Hawthorn Health & Dietetics.

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