Common Low FODMAP Diet Mistakes

We all know that the low FODMAP diet is not intended to be a forever diet. Instead, it is supposed to be used as a process to identify which foods are involved in those nasty explosions in your gut and where your threshold is for these. BUT, to successfully do this involves Rechallenging and Reintroducing FODMAPs. 

The Challenge phase is arguably the most complex part of the diet. When not done correctly it can be frustrating and confusing. But when done well it will give you food freedom!

These are the 6 mistakes I see people making with challenging FODMAPs and how to avoid them:

1. Using the wrong food to challenge with. 

Most foods are a combination of different FODMAPs (and of course other nutrients). Since during the Challenge phase we want to find out your tolerance for each individual FODMAP group, we want to choose foods that only contain FODMAP e.g. mango only contains excess fructose, so if you challenge with mango you can be sure of your tolerance to excess fructose.

On the other hand, if you challenged with cherries (which contain excess fructose and sorbitol) and had a reaction you wouldn’t know which FODMAP is the problem.

Bottom line: Once you know how you tolerate each individual FODMAP group, you can apply this knowledge to any food with any combination of FODMAPs.

2. Not using appropriate challenge serve sizes.

The great news is that FODMAP cut-offs are fairly conservative and we find that most people do tolerate larger serves. The best way to challenge is to start with a small serve and increase the serving size over a few days to a larger server. This will not only tell you if you are sensitive or not, but it will also tell you where your threshold is for that FODMAP.

Starting with a service that is too large may not help you find that smaller threshold that you do tolerate.  Not going large enough with your large serve may not push you enough to find your threshold.   

Bottom line: Using appropriate serve sizes will give you confidence in smaller serves and give you the info you need about where your threshold actually is.

3. Being unrealistic with Challenge results.

FODMAP isn’t about having no symptoms at all, some mild fluctuations day to day are actually very normal and reflective of a healthy balanced diet. It’s quite normal to have softer bowel movements after sorbitol or a bit of gas after onion or garlic.

What we want to avoid are the more painful symptoms that impact on your quality of life. So I encourage people to think about symptoms as mild, moderate or severe when analyzing challenge results.

Ultimately, in terms of mental and physical health, wellbeing and longevity the research are strong that food variety is an important part of a healthy diet and a healthy gut microbiome.

Bottom line: The FODMAP diet has three phases with the goal of achieving: as much variety as possible, with as few symptoms as possible.

4. Staying in Elimination for too long. 

FODMAPs are carbohydrate molecules that are poorly absorbed in the small intestine. They stay in the digestive tract and travel through to the large intestine (or colon) where they become fast food for the healthy gut bacteria that live there. Some foods are FODMAPs for everyone (but people with a sensitive gut are more affected than those without a sensitive gut) and are supposed to provide food for our healthy gut bacteria.

Limiting FODMAPs to strictly for too long can starve gut bacteria. If they are not able to get food the normal way, they will look to alternative sources (like the mucus layer within our digestive tract) or eventually die off.

Either of these situations can lead to an imbalance in gut bacteria and deteriorating gut health which can ultimately make IBS worse. 

Bottom line: FODMAPs are good for gut health, and poor gut health can worsen IBS

5.  Choosing the wrong foods in the wrong serve sizes.

The initial challenge phase is all about testing the FODMAP groups and not the foods. By choosing foods that only contain one FODMAP group, you can identify exactly how you react to each individual FODMAP and then relate that information to foods that contain multiple FODMAPs. 

Additionally, FODMAP tolerance is seldom black and white, most people will have a threshold for each FODMAP group. To find your threshold, we suggest starting with a small serve and increasing over a few days to a larger serve. This will not only tell you if you are sensitive to that FODMAP but it will also tell you how much of it you are ok with and where your threshold is. 

Bottom line: choose foods with only 1 FODMAP group, start with a small serve and increase over a few days to a larger serve

6.  Not eating a baseline low FODMAP diet during challenges.

So let’s be frank, if you are going to challenge FODMAPs there may be an instance that you trigger mild to moderate symptoms. It’s actually when we prove that we can trigger symptoms that we can confidently say that you have identified a sensitivity. Given this, it’s surprising how often I come across people who go out to dinner during a challenge and the next day when they are suffering are left asking themselves, was it the FODMAP or was it something in dinner last night.

Crazy right! If you are going to potentially cause yourself symptoms, make sure you get accurate info out of it by ensuring that the challenge food is the ONLY suspect food that you eat during a challenge. This way you can be absolutely sure it was the challenge food that is the culprit. 

Bottom line: To be confident in results, make sure the challenge food is the only high FODMAP food that you eat during a challenge. 

About The Author

2 thoughts on “Common Low FODMAP Diet Mistakes”

    1. Low FodMap Guy

      Hello Sarah,

      Look to stay within the Elimination period for around 2 months. If there is an issue in the elimination period, the move to on to the maintenance period.

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