A Dietitians Guide to Minimising IBS Symptoms – Part Two: Dietary Management of IBS


There are many options for managing IBS, but one common evidence-based approach is a low FODMAP elimination diet. The term FODMAP stands for Fermentable Oligosaccharides, Disaccharides, Monosaccharides and Polyols. These are forms of carbohydrates that once entering the large intestine are fermented in the large intestine as part of normal digestion.  We are yet to understand why those suffering from IBS are more sensitive to this process than those who do not suffer from IBS.

Common high FODMAP foods include onion, garlic, chickpeas, large quantities of flour, milk, apples, and mushrooms, but a comprehensive list can be found on the Monash Website.

The first step of management is to eliminate all high FODMAP foods from your diet for 4-6 weeks and if this is the cause to your symptoms, they should drastically resolve following this time frame.

If you found your symptoms resolve, it is essential to reintroduce foods back to your diet in a systematic fashion; this is the “challenge phase.” This phase of the diet is crucial in gaining an understanding of which FODMAP groups trigger symptoms for you and in what quantities. This process can be complicated and requires the support of an Accredited Practising Dietitian specialising in gut health. 

If your symptoms did not resolve, it is important to reintroduce these foods back to your diet as FODMAP containing foods are important sources of prebiotic fibres that have a positive impact on your gut health. To the same vain, an unchallenged low FODMAP diet over the long-term induces potentially unfavourable changes to the gut microbiota. Since it is unlikely that all the FODMAP food groups are triggers for symptoms in each individual when consumed in normal amounts, it is likely that many of these foods will be able to be reintroduced with minimal discomfort. The combination of these factors and the desire to keep as much flexibility in the diet as possible is why it is important to reintroduce as many high FODMAP foods that you don’t react to as possible.

RPAH Food Chemical Elimination Diet

If your dietitian suspects that a food chemical intolerance may be contributing to your IBS symptoms, they may instead recommend the RPAH diet which involves an elimination phase and a challenge phase of food chemicals, additives and preservatives.

There are four main groups of naturally occurring food chemicals and additives/preservatives that can elicit physiological responses such as gut reactions.  These include: salicylates, amines, glutamate and other additives. This can be confusing and once again is best done under the careful instruction of an Accredited Practising Dietitian specialising in food intolerances.


Certain types of probiotic supplements have been found to be helpful to reduce inflammation in the gut and improve the balance of bacteria in the gut. There is emerging evidence that probiotic supplementation can reduce the symptoms of IBS and improve quality of life, although more research is still needed.

There are many good probiotic supplements on the market.  Some specific Australian products that may assist with the management of IBS include most broad spectrum probiotics or those in powder form mixed with milk or naturally occurring in yogurt or medical grade VSL#3. While probiotic supplements in general are still lacking definitive dosing amounts, they have generally been shown to be beneficial.

Other Common Trigger Foods

Certain foods can be a trigger for IBS symptoms, even if they aren’t excluded in the low FODMAP diet or the RPAH elimination diet. Some of these foods include spicy foods, burgers, fish and chips, pizza and caffeine. Avoiding or limiting these foods can help to control symptoms in some people.


A review of 16 clinical trials investigating the use of peppermint found that it had a significant impact on reducing the symptoms in approximately one third of people with IBS. Peppermint appears to be beneficial for both diarrhoea and constipation as it relaxes the muscles in the digestive tract and improves digestion.


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