When you first start following the low FODMAP diet, ‘overwhelming’ is the word you’d use to describe it. So many rules, so many restrictions, so many details. But this isn’t a normal diet. It’s not for weight loss and it’s definitely not a fad diet. It’s to help you determine whether you have specific food intolerances that trigger your painful symptoms of Irritable Bowel Syndrome (IBS).

So while it’s easy to blow off an overly-restrictive and ineffective fad diet, it’s not quite so easy to blow off a diet that’s designed to get your digestive health back under control. Of course you can choose to cut corners and hope it won’t matter, but with a low FODMAP diet, YOU are the one who will notice.

But whether you deliberately choose to break the rules of the low FODMAP diet, or accidentally make a mistake (or unfortunately have the mistake made for you), the big question is:

“Does it matter if I accidentally ate something that was high in FODMAPs? And do I have to start all over again?”

Does it matter if I make a mistake on the low FODMAP diet? | A Less Irritable Life


What type of damage occurs when you make mistakes on a low FODMAP diet?

The first thing to understand about FODMAPs is that they don’t actually damage the gut. They can cause some rather spectacular IBS symptoms, but they don’t cause long-lasting damage. So when you eat high FODMAP foods, accidentally or deliberately, you may suffer quite badly for a few days but you will recover.

So since a FODMAP mistake doesn’t actually damage the gut, does it matter if you make a mistake on the low FODMAP diet? Do you have to start all over again?

Essentially the answer is ‘no’, you can get back on track and don’t have to start over. However, depending on which of the 3 phases of the low FODMAP diet you’re currently in, there could be other consequences to consider.


How do mistakes affect each phase of the low FODMAP diet?

Phase 1 (elimination/restriction):

In the initial phase of the low FODMAP diet, you’re bound to make mistakes. Remember that feeling of overwhelm I mentioned? That’s because the restrictions are complex, making it difficult to get it right from the first day. So even when you’re trying your absolute best, something will escape your attention and you’ll make a mistake.

But the good news is that you don’t have to be perfect.

The goal of the first phase is to see whether decreasing your FODMAP intake improves your IBS symptoms. So as long as you do the best you can, even with occasional mistakes, you should be able to see if the diet is helping. And if you do make a mistake, write down what you ate and the symptoms you experience. This can help to give clues about which FODMAPs you’re most likely to react to.

Phase 2 (reintroductions/tolerance testing):

While there’s never a need to be 100% perfect on a low FODMAP diet, this second phase is where mistakes will have the biggest effect. That’s because the goal of this phase is to test your tolerance to FODMAPs by reintroducing one specific FODMAP at a time and seeing how you react. But if you make mistakes at the same time as a test, you won’t know whether any reaction you experience was due to the FODMAP you were testing or due to the mistake.

So what should you do if you make a mistake in this phase? Take note of it and allow yourself to fully recover before starting a new test. It’s also a good idea to redo that last test so that you can be certain of the result.

Phase 3 (maintenance/modified low FODMAP diet):

This is the phase where mistakes don’t matter, except for how they make you feel. In this phase, you’ve done all the testing and should know what your body can and can’t handle. You’ll also be following a less strict version of the low FODMAP diet based on your personal tolerances.

In this phase, there will be times when you decide to push the limits and deliberately eat something that may be problematic, just to see the results. If you do react, then you’ll know you still have issues with that FODMAP and can go back to avoiding it. If you don’t react, then your ‘mistake’ becomes valuable information suggesting that your tolerance levels may have changed and you may be able to further expand your diet.


What’s the best strategy to prevent mistakes on the low FODMAP diet?

1. Make sure you know which foods are safe to eat and which are best avoided.

Essentially this comes down to making sure your food lists are accurate. This can be achieved as follows:

  1. Work with a FODMAP trained health professional who can provide you with up to date information.
  2. Use reliable apps that contain lists of low and high FODMAP foods. I recommend the Monash University Low FODMAP Diet app and the FODMAP Friendly app.

For further reading: Your guide to starting a low FODMAP diet


2. Make sure you check the ingredients of any meal or processed food against your food lists before you eat it.

This can be achieved be either speaking to the person who made the food (and if possible checking their recipe) or by looking at the ingredients panel if it’s a processed food. Once you know what’s in the meal or food item, you can check it against your food lists and make an informed decision about the FODMAP content.

Admittedly this step doesn’t always go to plan since sometimes you can’t get detailed information. Also, sometimes people forget some of the ingredients they used or don’t understand the importance of fully restricting certain ingredients. For instance, thinking that a tiny bit of onion or garlic won’t hurt is a common error that well-meaning family or friends may make when cooking for you.

For further reading: 5 essential tips for low FODMAP label reading


3. If in doubt, don’t eat it. Or, if possible, leave the part of the meal that you’re not sure about.

Your final decision here will depend on which phase of the diet you’re in, how hungry you are, and what other food options are available. As a general rule, I avoid all ‘treat’ or ‘snack’ foods that I can’t be confident about, even awesome looking cakes and desserts. But, I will occasionally eat a high FODMAP option if there’s no alternative and I’m starving, or if I know that I won’t be able to get a low FODMAP option in the next couple of hours.


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