The low FODMAP diet can be an effective tool in determining if certain foods are triggering irritable bowel syndrome (IBS) symptoms. These symptoms may include changes in bowel habits (diarrhoea, constipation, or a mix of both), abdominal pain and/or bloating and wind.

It is certainly not a cure-all diet and shouldn’t actually be the first line treatment approach for IBS. Often people will present to their GP or gastroenterologist and be given a one-pager low FODMAP diet to follow to help with their IBS symptoms, or they may google symptoms and find a list of what to eat and what to avoid. It is not uncommon for this approach to be ineffective (or not as effective as the dietary approach could be), as it’s not looking at the whole picture of what may be happening in your life and is not approaching the diet as the 3-step approach that it is intended.

The 3 steps for the low FODMAP diet involve eliminating high FODMAP foods from the diet, if there is symptom improvement you then move on to the reintroduction phase where each category of FODMAPs is tested to determine a tolerance level, and then a more personalised plan is created to help best manage symptoms, while having a varied and healthful diet that includes being able to enjoy eating socially.

Below are some of the reasons why a low FODMAP diet may not be working for you.

You have been on the elimination phase for too long. The elimination phase is not intended to be a long-term diet. It is the first phase of the diet, that is useful in determining if any of these foods are having an impact on gut function. The elimination phase of the diet is very restrictive and cuts out a lot of healthy foods that are prebiotics, or a food source for our healthy gut bacteria. Studies have shown that decreasing the FODMAPs in our diet can lead to a reduction in beneficial bacteria in the gut, and individuals with decreased beneficial gut bacteria have furthermore been shown to have greater pain scores in IBS (1,2). This means that if the elimination phase of a low FODMAP diet is followed for too long it can actually increase your sensitivity to these FODMAPs and may cause greater IBS symptoms.
There are other dietary triggers for your IBS that are not FODMAPs. As I said above, the low FODMAP diet shouldn’t be the first line treatment approach for individuals with IBS. It is helpful to first look at gut irritants such as caffeine, alcohol, spicy foods and fatty foods as often being mindful of the consumption of these foods can lead to significant symptom improvement.
You have cut out FODMAPs but haven’t looked at the fibre in your diet so you are now experiencing constipation. It can be common for individuals to start out experiencing diarrhoea or mixed bowel habits, only to develop constipation when trialling a low FODMAP diet. This happens for a couple of reasons, firstly many FODMAPs are osmotic, meaning they draw water into the digestive tract, this is what can cause diarrhoea in some individuals, but also helps with regularity in others. Secondly, if we are not being mindful of including plenty of high fibre, low FODMAP foods in our diet, the diet can become very low in fibre. As we know, fibre and fluid are essential factors in keeping bowels regular. If this is the case for you I would encourage you to persevere with the reintroduction phase, so you can include some of these osmotic foods back in your diet, and also to get in touch with your FODMAP trained dietitian to work out an approach to help manage the constipation.
You haven’t addressed your stress levels. More and more research is showing that the gut and brain are linked and are in constant communication. You have probably noticed this yourself, perhaps rushing to the toilet before a big exam or experiencing butterflies before giving a speech. Experiencing stress is normal, it has a very important role in pushing us to take action, we call this the ‘fight or flight’ response, it prepares our body to fight or run if we are faced with danger. The problem arises when we are under chronic or long-term stress and the fight or flight response is being activated continuously. This can be associated with an increase in gut symptoms, because when we are in fight or flight mode, our ability to rest and digest decreases. Including stress management strategies is therefore an important piece of the puzzle when learning to better manage your IBS symptoms.
Your eating is erratic and when you do eat meal sizes are large. Large meals can cause gut discomfort and bloating, and can cause individuals with IBS-D to rush to the toilet after eating due to the gastro-colic reflex. The gastro-colic reflex is stimulated by eating and helps to make room for the food we are eating. It is much more manageable for our digestive tract to have smaller, more frequent meals and this can be a very effective strategy in helping to manage bloating or rushing to the toilet after eating.
You are not eating enough. Under nutrition can cause many of the same symptoms as IBS, but the solution will be ensuring regular and adequate nutrition, not an elimination diet.
You are one of the 25% of people who will not get relief from the diet. Not everyone will find that their IBS symptoms improve on the low FODMAP diet. The diet has been shown to be effective tool to help around 75% of individuals with IBS improve their symptoms, but that leaves around 25% of individuals whose symptoms will not improve on the diet. There are other IBS therapies that can be trialled if this is you, be sure to talk to your dietitian to discuss the different options available.

Please note that the information in this article is general in nature, everyone has individual requirements and individual recommendations will vary. If you would like support to help navigate your IBS or food intolerances, please get in touch, I provide telehealth nutrition counselling for individuals struggling with food and eating. I’d love to hear from you and would love to support you in finding a balanced approach that helps to manage your gut symptoms and improve your quality of life.

References:

1. Staudacher HM, Lomer MC, Anderson JL, et al. Fermentable carbohydrate restriction reduces luminal bifidobacteria and gastrointestinal symptoms in patients with irritable bowel syndrome. J Nutr. 2012;142(8):1510–1518.

2. Halmos EP, Christophersen CT, Bird AR, Shepherd SJ, Gibson PR, Muir JG. Diets that differ in their FODMAP content alter the colonic luminal microenvironment. Gut. 2015;64(1):93–100.

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Why The Low FODMAP Diet May Not Be Working For You