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Introduction to a low FODMAP diet by Dr Megan Rossi

Introduction to a low FODMAP diet by Dr Megan Rossi

by FoodMaestro | 25 May 2016

Introduction to a low FODMAP diet - By Dr Megan Rossi 

Have you heard about the low FODMAP diet, but not quite sure what it’s all about?

The low FODMAP diet is rapidly gaining popularity, however, unlike the myriad of “fad” diets out there, the low FODMAP diet has been carefully and specifically developed for people with Irritable Bowel Syndrome (IBS) and importantly it is backed up by clinical research.

IBS is a chronic functional bowel disorder that affects around 1 in 10 adults in the UK. Its sufferers experience a range of symptoms including gastrointestinal pain, bloating, wind and change in bowel habits. If you are reading this and thinking these symptoms sound familiar and are impacting your quality of life, it’s recommended you consult your doctor to rule out other causes of those symptoms such as coeliac disease and inflammatory bowel disease.

Once you’ve been diagnosed with IBS the symptoms can be managed using several strategies including diet and medication, although diet is generally preferred by most and considered a cheap and safe option. First line dietary advice for IBS includes assessing intakes of spicy food, caffeine, alcohol, dietary fibre and fluid. For those who don’t respond to first line advice, that’s where the low FODMAP diet comes in.

So how can the low FODMAP diet help?

FODMAPs are a group of fermentable carbohydrates that are found in a wide range of foods. Without getting too technical the word FODMAP stands for - Fermentable Oligosaccharides, Disaccharides, Monosaccharides and Polyols- which are the scientific names given to different groups of carbohydrate based on their chemical structure.  It’s a lot to digest I know but Table 1 helps break things down. Within each of these carbohydrate groups there are specific carbohydrates which are restricted on the low FODMAP diet. 

Table 1: Carbohydrates relevant to the low FODMAP diet


These specific carbohydrates are thought to worsen gut symptoms because unlike other carbohydrates (such as glucose which falls under the monosaccharide carbohydrate group) they’re not completely absorbed by our body.

This creates issues in people with IBS through two main mechanisms:

1) FERMENTATION: The undigested carbohydrates that enter the large bowel are rapidly fermented by the community of bacteria (yes did you know our gut is home to trillions of bacteria?!). This can lead to various symptoms such as bloating, wind, pain and altered bowel habits.
: The undigested carbohydrates can draw fluid from the body into the gastrointestinal tract, which can further exacerbate these unpleasant, and often distressing symptoms.

Okay, that’s enough about the science, let’s get into the practical side of the low FODMAP diet.

First and foremost, where are these FODMAPs found?

Like we talked about above, FODMAPs are actually present in most food groups which can make the diet tricky to follow without good quality resources (like the low FODMAP app!).

To start with it’s helpful to remember that FODMAPs are carbohydrates so if a food doesn’t contain any carbohydrates such as meat, egg, fats and oils it is safe to say they are FODMAP-free (unless of course they’ve been marinated or substituted with carbohydrates).

So the next question is, what does the diet involve?

Unlike many other diets, it is not recommended you follow a strict low FODMAP diet for longer than 4-8 weeks, for reasons I will discuss in a future post. Instead, a personalised FODMAP diet tailored specifically for you is recommended for long term symptom management. Designing your personalised FODMAP diet involves three stages:

1)      Restriction stage: This is what people commonly refer to as the low FODMAP diet, in that you restrict all the FODMAPs from Table 1 in your diet. It may help to think of this as your baseline diet, the foundation to build on.

2)      Reintroduction stage: Once you have followed the restriction stage for 4-6 weeks and have achieved adequate relief of your symptoms, it is time to carefully reintroduce each of the different FODMAPs, testing one at a time. This stage will help you identify which FODMAPs you’re most sensitive to and further to establish your threshold dose ie. how much you can tolerate before symptoms are triggered. It is important to note that unlike most food allergies, people with IBS can tolerate small amounts of FODMAPs. It’s the total FODMAP load of your diet that is most important.

3)      Personalisation stage: This is also known as the modified or personalised FODMAP diet and is a combination of stages 1 and 2. The personalised stage is a version of the low FODMAP diet that has been tailored to your personal tolerance identified in stage 2. It is important to progress to stage three to give your diet the flexibility and variation, which is key to long term compliance and importantly improved quality of life and health.

I know many of you are probably reading this feeling slightly overwhelmingly by the complexity of the diet…and that’s where the FODMAP by FM can help. In fact, the complexity of the diet provoked IBS-experts, Prof Kevin Whelan and Dr Miranda Lomer, from King’s College London to team up with Food Maestro to develop the app. The app is now used widely across the UK as a tool to guide people with IBS through each of the three stages in collaboration with their dietitian. I believe it’s about all working as a team to provide the expertise and tools necessary for long-term success and a healthy happy life.

I hope this brief introduction has provided you with greater insight into the low FODMAP diet and whether it’s right for you.

Want to know more?

Stay tuned for my next blog looking at the research behind the diet.

Related articles by Dr Megan Rossi in the irritable bowel syndrome (IBS) series:

  1. Introduction to a low FODMAP diet - By Dr Megan Rossi 
  2. The research behind the low FODMAP diet -  By Dr Megan Rossi 
  3. Lactose guidelines for the FODMAP diet by Dr Megan Rossi
  4. Beyond the low FODMAP diet By Dr Megan Rossi
  5. Why the low FODMAP diet may not be working for you

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