5 Common Mistakes When Reintroducing FODMAPs

5 Common Mistakes When Reintroducing FODMAPs

Photo Credit: ‘Fresh garlic on wooden table‘ by Jag_cz licensed under Shutterstock Standard Image. Edited by A Little Bit Yummy.

Foreword by Alana: The reintroduction phase of the low FODMAP diet can feel overwhelming and it is easy to make mistakes. However there are plenty of steps you can take to make the re-challenge and reintroduction process a success. Registered dietitian, Lee Martin, is a low FODMAP researcher who specialises in the FODMAP reintroduction process. He has written a best practice guide that walks you through the re-challenging and reintroduction process. In this article he shares his reintroduction tips to make sure you avoid the top five common mistakes when reintroducing high FODMAP foods.

Top 5 Common Mistakes When Reintroducing FODMAPs

1. Choosing the wrong food to test with. Solution: Only choose foods containing one type of FODMAP when testing tolerance levels.

We know that some foods contain one type of FODMAP while others contain multiple FODMAPs. When working out your own tolerance levels to individual FODMAPs it is important to only use test foods that contain one type of FODMAP. Otherwise you cannot be certain which FODMAP is actually causing symptoms. For example, when re-challenging fructose it would be better to test with mango instead of an apple, because apples contain both excess fructose and sorbitol.

Also be aware that some re-challenge foods suggested in the past are now no longer supported. When I completed the Kings College London low FODMAP diet training course for registered dietitians in 2013, the advice for testing the polyol mannitol was to use mushrooms. A year later King’s College London then changed this advice because mushrooms at higher portion sizes were found to contain fructans. This meant that as you increased the portion size of mushrooms over the 3 day testing period you were eating both mannitol and fructans. If you started to get symptoms it would be difficult to determine whether it was the mannitol or the fructans triggering symptoms. (An example of how mushrooms used to be tested is found on my old blog post on reintroducing FODMAPs).

This is relatively new and updated advice on reintroducing FODMAPs. There are several old internet sources which advise testing foods that contain more than one type of FODMAP. I discuss this misinformation on the internet in my article: Reintroducing Foods on the Low FODMAP Diet Watch Out For Misinformation. For an accurate overview of the re-challenging and reintroduction process check out Alana’s article: Testing FODMAPs – How Does the Reintroduction Phase Work.

2. Being unrealistic with your re-challenge tests: Solution: Re-challenge with foods you would normally eat.

Make your FODMAP re-challenges realistic. Do not choose a test food that you wouldn’t normally eat just because a book or a website suggests it. Choose the most suitable foods for you and your normal dietary patterns. For example, garlic is a commonly used test food for fructans found in vegetables. If you do not like garlic or do not use it often in cooking then this is not a sensible food to choose. Remember it is the FODMAP you are testing not the food, so as long as you are choosing a suitable food to test, it doesn’t matter what food you eat.

3. Testing with portion sizes that are too large. Solution: Choose sensible portion sizes.

The best way of working out your tolerance levels to individual FODMAPs is to start with a small amount of FODMAPs (in a small portion size of the food), and then gradually increase the amount of FODMAPs by increasing the portion size of the food. As previously mentioned, it is the FODMAP you are testing not the food. You are trying to find your tolerance level by consuming a portion size of the food that gradually increases the amount of FODMAPs you are trying to re-challenge. My book and other information sources suggest portion sizes for foods, which are based on the amount of FODMAPs found in the food rather than your typical portion size.

Think sensibly about the portion sizes of foods when re-challenging. If you would never actually eat the suggested large portion size of the food then there is no need to complete that test. For example, when you test fructans in wheat and other grains you use bread. On the first test day you eat one slice of wheat bread, on the second test day you would eat 2 slices of wheat bread and on the third test day it would be three slices. If you would never normally eat three slices of bread at one time then why would you do this now? If you do tend to eat three slices of bread but spread throughout the day, then this is how you should complete the third test. In this example you may choose to eat one slice of bread at breakfast and two slices at lunch if this is what you normally do.

Another common portion mistake people can make is starting with a portion size of food that contains a high level of FODMAPs. Some internet sources suggest testing with 1 whole clove of garlic when testing tolerance levels to vegetable fructans. Eating an entire clove of garlic means you are already consuming a very high amount of fructans, which will more likely trigger symptoms before a tolerance level can be detected. Instead try starting your test with ¼ of a clove of garlic.

4. Not allowing symptoms to settle before the next re-challenge. Solution: Have a ‘washout period’ between every test.

At the end of each FODMAP test you need to make sure you are symptom free before starting a new test. This is known as the ‘washout’ period. Typically a 3 day washout period is all that is needed before starting a new test, however if you are still experiencing symptoms even on day 3 of the washout period, then you need to wait until you are free of symptoms before starting the next FODMAP test.

If you feel you are rarely symptom free (even when following a low FODMAP restriction diet) then you will need to make your own decision as to whether or not to start a new test. This decision should be based on if you feel your symptoms have reduced to a baseline level that is usual for you. If you have reached your symptom baseline, then this would be the correct time to start the next test.

While it is tempting to just plough through the re-challenge phase without questioning instructions like the low FODMAP restriction diet, it is important to take your time. The reintroduction phase is a lot more complex than the low FODMAP restriction diet, and individual preferences and symptoms need to be considered even more.

5. Eating high FODMAP foods during re-challenges. Solution: Only reintroduce FODMAPs at the end of the re-challenging process.

It is really important that once you have tested a FODMAP you do not reintroduce it back into your diet until the end of the re-challenging process. Even though you may have eaten a FODMAP and not reacted to it, you still need to remove that FODMAP from your diet and continue to follow a low FODMAP restriction diet while testing the other FODMAPs. If you start to reintroduce FODMAPs then this will increase your overall FODMAP load and can increase the chances of you experiencing symptoms. This can affect the accuracy of the re-challenging process as you may not be able to work out which FODMAP is triggering your symptoms. Often it is the total load of FODMAPs rather than the individual FODMAPs that trigger symptoms, which is why you only test one FODMAP at a time while following a low FODMAP restriction diet in the background. This is the best method to help you understand what individual FODMAPs are your particular triggers.

Need More Help?

Detailed information on the reintroduction phase of the low FODMAP diet can be found in the self-help guide ‘Re-challenging and Reintroducing FODMAPs’, which includes a detailed protocol for the entire reintroduction process and reference tables of all foods suitable for re-challenge tests. This guide will help the re-challenging and reintroduction process feel more manageable and help you look forward to successfully reintroducing high FODMAP foods back into your diet.

About Lee Martin (RD)

Lee Martin (RD)

Lee Martin is a FODMAP trained registered dietitian in the UK. In 2014 Lee took up an academic role at King’s College London and is working within the FODMAPs team researching the low FODMAP diet. Lee has specialised in the FODMAP reintroduction process and has written a best practice guide that walks you through the re-challenging and reintroduction process. Lee and his partner are currently travelling around the world and talking about their low FODMAP experiences. You can follow Lee on his website or on Twitter.


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  • Joyce 11/01/2016 5:15pm (23 months ago)

    This is super-useful information! There is so much information out there about the elimination phase of the low-FODMAP diet, but not a whole lot about re-introducing FODMAPs. Right now I've successfully re-introduced garlic (hooray!) and am taking a rest before I start the next re-challenge. I really appreciate all the support this blog provides!

    • Alana Scott 11/01/2016 8:29pm (23 months ago)

      Hi Joyce,
      I'm glad you found Lee's article useful! If you need more information about re-introducing FODMAPs then I highly recommend Lee's book. Well done on testing garlic - I'm glad to hear you pasted that re-challenge. I look forward to hearing how the rest of your re-challenges go.

      • Joyce 12/01/2016 5:38pm (23 months ago)

        I do indeed have the book. It's a huge help!

        • Alana Scott 12/01/2016 10:38pm (23 months ago)

          It is a fantastic book and I highly recommend it as well. Here is a link for anyone who is interested: http://www.reintroducingfodmaps.com/

  • Trine 12/01/2016 9:33am (23 months ago)

    This article helped me a lot. I'm trying to get my self together to start reintroducing after one year more or less on a resticted diet.

    But I have one question: It says in the article to be aware that I'm testing a fodmap and not certain kind of food. Does that mean that I can test eg. fructose by only testing mango or do I need to test other kinds of fructose?

    I'm going to see if I can find this book in Denmark. It sounds to be very usefull.

    Thank you :-)


    • Alana Scott 12/01/2016 10:45pm (23 months ago)

      Hi Trine,
      What the article was trying to explain as long as you choose a food that is high in the FODMAP you are testing (eg fructose) then it doesn't matter which approved food you choose to use. For fructose this could be mango, honey, boysenberries, feijoa, canned tomatoes etc. What is most important is you choose a test food that only has one FODMAP and that you gradually increase the portion size over three days. This means you should try and choose a food that you would normally eat that is high in the FODMAPs that you want to test.

      • Trine 26/01/2016 3:07pm (22 months ago)

        Thank you ?

        It seems so overwhelming. I thing that my biggest fear in this is testing the wrong ammount of eg honey. We only have very little literature in Denmark on the topic so I'm worried that I might get it wrong testing the different groups of fodmaps by testing the wrong amount.

        Do you know any place where I can read more which amount to test? I tried finding Lee Martin's guide but it only exists on Kindle.

        Thank you for such a good informative and inspiring webside.

        • Alana Scott 26/01/2016 6:58pm (22 months ago)

          Hi Trine,

          I know the reintroduction phase can feel very overwhelming. I borrowed a kindle from a friend for a day so I could read Lee's book. You can find more information about which foods to test and in what amounts in this article: http://www.alittlebityummy.com/re-introducingfodmaps/ - Have a look at the re-challenge table in the article. Then let me know you have more questions.
          Thanks for the lovely feedback :-)

  • Alleigh 12/01/2016 8:26pm (23 months ago)

    Alana...I just wanted to say thank you. I discovered your blog about 7 weeks ago, right around the time I was starting the FODMAP restriction diet. Your thoughts and suggestions on navigating both the immediate challenges of FODMAP elimination, along with the more longer-term ones of reintroduction and living a modified low-FODMAP lifestyle have really help make a difficult process much more approachable. So, THANK YOU!

    • Alana Scott 12/01/2016 10:37pm (23 months ago)

      Hi Alleigh,
      Your comments have just made my day! It is such a pleasure to be able to help you on your FODMAP journey. It is great to know that you are finding my website helpful as your progress through the different stages of the low FODMAP diet.
      Thank you again for commenting.

  • Jeanne 16/01/2016 11:07pm (22 months ago)

    The support I have found here has been amazing. I have 5 weeks to go before I start re-introducing but trying to learn the right way to do it. Thanks so much to those who have worked all this great info out!

    • Alana Scott 16/01/2016 11:26pm (22 months ago)

      Hi Jeanne,
      I'm so happy that you are finding the resources here useful! Lee Martin is a very experienced dietitian and it was wonderful to have him share his knowledge with us!

  • Jane McEwen 26/06/2016 12:00am (17 months ago)

    What can I drink at Starbucks? What yogurt can I have? How about eating sweet potatoes?

    • Alana Scott 26/06/2016 8:33pm (17 months ago)

      Hi Jane,

      Okay so choose a lactose free yoghurt that doesn't contain added high FODMAP ingredients (these could include honey, inulin, high fructose corn syrup, agave syrup, or high FODMAP fruit). Sweet potatoes can be enjoyed in small 70g or 1/2 cup serves, but become high FODMAP in larger serves so watch your portion size carefully.

      In terms of Starbucks you might like to read this article from our friends over at Nicer Foods. It talks about how to select a safe coffee: https://nicerfoods.com/low-fodmap-coffee-shop-options/

      I hope that helps.


  • Martine 18/10/2016 1:21pm (13 months ago)

    I've been on the diet for over 2 years now and am feeling so much better. I still have periods where I do experience symptoms. Do I go back to square one and retest everything or just test what I think it may be (polyols). Also I would never eat the large portion of anything so can I just test small and medium portions for 2 days and then do the 3 day wash out period or should I lower the amounts and still test for 3 days. Thanks for your help, it is great to be able to go somewhere now, when I first started there was very little information.

    • Alana Scott 18/10/2016 8:03pm (13 months ago)

      Hi Martine,

      Have you been using a modified low FODMAP diet? This means you have been eating a few high FODMAP foods. If you have been then I would suggest going back onto the strict elimination phase for a week or so and see if your symptoms settle. If they don't settle you might want to check in with your doctor or dietitian.

      Once your symptoms are settled you can start testing. You can do the challenge tests in any order you choose, and if you know your sensitivity to a certain group hasn't changed, then it is up to you to determine if you want to test it.

      You can test with the small and medium portions. I would suggest for your third day to use the medium portion size again, which will just help you confirm whether or not you cope with that portion size. Then go into your wash out period before start the next test.

      I hope that helps.


  • Angela sambusida 30/10/2016 5:38am (13 months ago)

    I wonder if the onion fructans is suggested 1/4,cup of onions is cooked or row? Who can give me the answer ?

    • Alana Scott 30/10/2016 7:57pm (13 months ago)

      Hi Angela,

      You can test high FODMAP foods raw or cooked. Think about how you would normally eat the food and use that to test. For example, if you normally eat onion cooked with steak, then that is how you can test it. Let me know if you have more questions.


      • Amy 16/04/2017 12:22am (7 months ago)


        Hope you might be able to help with a reintroduction question related to the Lee Martin group "Fructans: Bread, cereal and grains." Why do you need to rechallenge two different foods containing fructans in this category since it's the FODMAP not the food we are testing? And do you rechallenge, for example, bread in increasing amounts for 3 days, wait 3 days, and then rechallenge, for example, pasta for three days? If they are both wheat why two separate challenges?

        Thanks so much for clarifiying!


        • Alana Scott 17/04/2017 6:37am (7 months ago)

          Hi Amy,

          That is a great question! Fructan containing grains are a bit tricky. People often react very differently to wheat based bread to how they react to wheat based pasta. This might be due to the manufacturing process and how it alters FODMAPs or due to other ingredients in the products. This is why we often get people to try a couple of different options in this category to see if they have any tolerance levels.

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