Understanding FODMAPs Part 3 - IBS and the Low FODMAP Diet

Parts 1 and 2 of the Understanding FODMAPs series gave a great explanation of what FODMAPs are, now in part 3 we will talk about when and how to use the low FODMAP diet, specifically for those with IBS. 


Irritable Bowel Syndrome (IBS)


IBS can be a poorly understood condition, even by the people who have it however despite a general lack of understanding about the condition it is becoming more common with one in seven New Zealanders having the condition. IBS is a chronic (meaning long term) functional bowel disorder that commonly presents with symptoms such as abdominal pain, bloating, diarrhea and constipation. However, these symptoms can flare up and change over time which can make it frustrating for people who have the condition. 


Now, the exact cause of IBS is unknown and is thought to be likely multifactorial. The best available evidence at the moment tells us there are a few things that could contribute to IBS: 

• The first of these is a previous gastrointestinal infection, sometimes referred to as post-infectious IBS. Essentially this when someone gets an infection in their stomach/intestine from a bug and once the bug has been cleared the symptoms described above persist.  
• Studies have also shown that there is a difference in the collection of gut bacteria in those with IBS vs those without IBS. However, whether this is the cause of the IBS in the first place or just a result of the IBS is not understood. 
• We also know there is a strong connection between our brain and the gut and it has been proposed that for some people increased stress and trauma can be a trigger for them developing IBS. We also see in people with IBS a phenomenon called visceral hypersensitivity. This essentially means they are more sensitive to changes in pressure in their intestines compared to someone without IBS.

Low FODMAP Diet in IBS


There is a range of therapies that have been proposed to treat IBS, ranging from probiotics and various supplements to changes in diet. One of the most effective therapies, helping around three out of every four people with IBS is the low FODMAP diet. 


Using the low FODMAP diet for IBS is done in three phases and you must complete all three phases/don’t stay in phase one of the diet. The way it works is by reducing the amount of FODMAPs you consume you also reduce the amount of pressure in your intestine as FODMAPs are great for producing gas and holding excess water in your gut.


Phase One - Strict Low FODMAP


As the name suggests, in this phase of the diet you are consuming only those foods that are classified as being low FODMAP. Now it is important to note that unlike an allergy where you need to avoid the allergen, in this phase of the diet you can have some FODMAP intake it just needs to be low. Here is an example of what I mean.


Take almonds as an example. They contain the FODMAP GOS (if you don’t know what that means, head to part 2). A serving of 10 almonds only contains a low amount of GOS and therefore is still okay to consume during phase one of the diet. However, 20 almonds contain a high amount of GOS and therefore would be too large of a serving size. The best currently available way to know whether a food is high or low FODMAP is to download the Monash University low FODMAP app. Monash University was the founder of the low FODMAP diet and hence (IMO) they have the best available resources when it comes to FODMAPs. 


You should follow phase one for 2-6 weeks, if you experience significant improvement in your symptoms then move to phase 2 of the diet. If you don’t experience an improvement then you must go over this with your dietitian who will reassess your diet. If you are still not experiencing any benefit from the low FODMAP diet then you must stop following the diet and try some of the other therapies available for IBS. This is also why I would recommend going through this whole process with a dietitian as it can be confusing as to whether you are following the diet correctly or not.


Phase Two - Reintroduction


During this part of the diet, you are trying to identify which FODMAPs, in particular, you react to and at what doses. The way you will do this is by keeping your base diet low in FODMAPs and then one at a time you will challenge each FODMAP group (refer to part 2 if you don’t know what the FODMAP groups are). 


These challenges work by you choosing a food high in just one FODMAP and having that food three days in a row, in increasing quantities to provide a moderate dose, high dose, and then your normal serving size of that food. After the first day you will assess whether there has been a flare-up in your symptoms or not, if there haven’t you will progress to the day 2 dose. If your symptoms are triggered by a dose then you can try that food in a smaller serving or stop that challenge completely. Once you have completed a challenge you should have a two to three-day washout period where you go back to eating low FODMAP before trying the next challenge. 


Here’s an example of a challenge for the FODMAP lactose:


Day 1: ¼ Cup of Cow’s milk
Day 2: ½ Cup of Cow’s milk
Day 3: 1 Cup of Cow’s milk 


Once you have gone through phase 2 you should have a list of your tolerance levels for each FODMAP and can then move to phase 3. 


Phase Three - Personalisation


In the final phase of the low FODMAP diet, you will take the results from your FODMAP challenge and create a new modified version of the low FODMAP diet that only restricts those FODMAPs/quantities of FODMAPs that you reacted to in phase 2. 


This is an important step as the strict version of the low FODMAP diet is NOT a healthy diet. Many foods high in healthy prebiotic fibre are also high in FODMAPs and are therefore missing from the diet in phase 1. Studies have also shown that following a strict low FODMAP diet can reduce the number of beneficial gut bacteria we have which further emphasizes the need to go through all three phases of the diet. The other consideration for going through all three phases is the toll going low FODMAP can have on the quality of your life. It can make cooking for yourself difficult enough let alone trying to socialize with other people or eating out. 


You can then continue to eat with your personalized low FODMAP diet. It is recommended that you try to rechallenge those FODMAPs you reacted to in the future as your tolerance to FODMAPs can change over time. 


Summary


IBS is a chronic functional bowel disorder that can affect anyone. Its cause is not fully understood however it is thought that those with IBS have a highly sensitive gut and so following a low FODMAP diet can be helpful in 70-80% of people with IBS as FODMAPs lead to increases in pressure in our intestines. If you do decide to follow the low FODMAP diet you should do this with a dietitian and you must not remain on phase one of the diet. 


Thanks for reading. 


Marco

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