There is information in abundance on the internet on the low FODMAP diet with much of it conflicting and confusing. Undertaking a trial of the diet based on food lists alone rather than under the guidance of a dietitian may result in:shutterstock_194900582

The low FODMAP diet trial completed incorrectly

Many people go to a lot of hard work trying to undertake the diet, only to miss things like:

  • soy milk
  • chewing gum
  • hidden ingredients in processed foods
  • excess intake of low FODMAP fruit
  • supplements containing high FODMAP ingredients  such as inulin/FOS
  • Wrong type of spelt bread
  • Multiple foods containing moderate levels of FODMAPs (particularly fructans)  consumed in excess


Over-restricted diet

The low FODMAP diet is often over-restricted.  For instance, exclusion of all fruit / all gluten-containing products and all dairy products.  Many foods containing FODMAPs are allowed in smaller quantities but end up often being completely excluded when there often is no need.


Lack of understanding of how FODMAPs alter gut function

In people with functional constipation/IBS-C,  removal of some FODMAP groups (e.g. sorbitol) or a reduction in fibre intake (a common occurance on the low FODMAP diet) may further contribute to constipation. Having an understanding on the effect FODMAPs exert on the gut is important. Worsening of constipation can increase bloating, gas and abdominal discomfort.


Reduced nutrient intake

Reduced nutrient intake can often occur particularly if the person has additional food intolerances/allergies or alternative diets (vegetarian or vegan diet). Care needs to be also taken for people with a history or existing nutritional deficiencies.


Inappropriate low FODMAP trial for children

Working with a dietitian who has experience with children and IBS is crucial to ensure optimal nutrition when undertaking the diet. In many cases, a more relaxed version of the diet can be just as effective with toddlers and older children.


Unsure of suitable brands

Having the knowledge of appropriate brands, where to buy these products and which products to be cautious of can help with food purchasing.


Staying on the diet long term

Many people are unaware of the importance of food-rechallenges once the elimination phase is finished. In many cases the diet is inappropriately adhered to rigidly for long periods of time. The low FODMAP diet is ideally only to be used for a short period of time (2-6 weeks) to determine whether these foods are affecting gut function. Research shows that long term FODMAP restrictions reduce intake of prebiotics which are important for good gut health. A low intake of prebiotics can lead to a diminishing response to the diet over time (i.e. becoming more sensitive to FODMAP containing foods) with deterioration of healthy gut bacteria.


Trialling the wrong approach or limited response to the diet

70-75% of individuals with IBS respond well to the low FODMAP diet however many other possible food intolerances exist. When working with a dietitian experienced in IBS/functional gut disorder (FGD), an alternative elimination diet may be advised if symptoms are suggestive of other intolerances. Many people can have a range of intolerances (e.g. FODMAPs AND food chemicals) and may report a partial response only to the low FODMAP diet as a result.


Trial not appropriate

Often the diet is undertaken with little medical investigation. There are many possible causes of gut dysfunction and IBS/FGD should only be suspected if a complete medical work-up has been performed by a GP and / or a gastroenterologist. Removing wheat from the diet can also delay the diagnosis of coeliac disease or make excluding coeliac disease challenging as many people are reluctant to gluten-load prior to testing (which is required for accurate diagnosis), particularly if the perceive wheat to be problematic.


Limited response as may require combined approach

The low FODMAP diet can often be used in combination with other therapies (e.g. pelvic floor physiotherapy or gut-focused hypnotherapy) and may be more effective than used in isolation. Working in a team situation with a dietitian and a gastroenterologist can also help with coordinating your approach to ensure nothing is missed.


Incorrect rechallenging

Different FODMAPs move through the gut at different rates and many people report delayed reactions. Reintroducing FODMAPs under the guidance of a dietitian will ensure you re-challenge correctly, so you can capture how your body copes with FODMAPs accurately.


Nick Dunn

Consulting Dietitian

Nick consults at our Glen Iris, Moonee Ponds, Greensborough, Hampton, Werribee and South Melbourne locations.