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How To Complete the Re-Challenge Phase

If you’ve finished the elimination phase of the Low FODMAP Diet, you’re probably feeling pretty good. This can make it hard to transition into the re-challenge phase. Especially when you know you’ll probably trigger your symptoms at least once. Even if you’re ready to start testing, it can be hard to find information on how to complete the re-challenge phase.

So, in this article, we’ll talk about why you need to move on from the elimination phase; how to complete your re-challenge; and what comes after. Hopefully, this information will make the transition a little easier. Let’s get started!
Doughnuts on yellow background with text overlay: How to Re-Challenge FODMAPs

Do You Really Need to Re-Challenge?

Even though it can be tempting to stay in the elimination phase forever, the Low FODMAP Diet is a diagnostic tool, not a long-term solution. In fact, research shows that limiting high FODMAP foods can be dangerous for your gut health.

According to Monash University, Stanford University, and The Journal of Nutrition, limiting prebiotics over long periods of time has been linked with a loss of good gut bacteria. Since many high FODMAP foods are prebiotics, staying in the elimination phase for too long can harm your gut.

In case you’re not familiar with prebiotics, the World Gastroenterology Organization describes them as things we eat that are indigestible and have a positive impact on our gut flora. Think of them like a bagged lunch for your good bacteria.

So, what does this have to do with you? According to The Journal of Nutrition, good bacteria begin to starve within 4 weeks of starting the Low FODMAP Diet. Research shows the first type of bacteria affected is “luminal bifidobacteria.” This specific bacteria is linked to changes in the immune system and abdominal pain, so it’s a good idea to keep it healthy.

Stanford University has also warned that changes in your gut bacteria due to a low fiber diet may be irreversible. This means it’s in every patient’s best interest to reintroduce high FODMAP foods as soon as possible.


How to Re-Challenge FODMAPs

Now that you know why it’s important to re-challenge, let’s talk about how to get it done. There are a few options when it comes to re-challenging FODMAPs. The system you choose depends on how you (and your healthcare team) think you’ll react to testing. Your options include what I like to call classic systematic testing, cautious systematic testing, and the FODMAP freestyle. Each method is outlined in more detail below.

The process of testing is pretty straightforward. You’re ready to start your re-challenge if you’ve completed at least two weeks of the elimination phase and your symptoms have been stable for 7 days straight.

To test a FODMAP group, choose a food containing one FODMAP and eat it in increasing amounts over 3 days. This is followed by a “washout” period.

The washout period is pretty important. It gives your body time to flush out the FODMAPs you’ve eaten during each test. It also gives your body time to recover from any symptoms you’ve experienced. This means you’ll start your next test with a clean slate. If you don’t wait for your system to recover, you can skew the results of your next test. So, cutting your washout period short to save time can cost you in the long-run.

Just so we’re clear, except for the food being tested, you stay on the elimination diet during your re-challenge. Food from groups you can tolerate will be added to your long-term diet in the third and final phase.

Classic Systematic Re-Challenge

Classic Systematic Testing

Using this system, a food containing one FODMAP is eaten in increasing amounts over 3 days. This three-day testing schedule will give you two important pieces of information. First, it will tell you if you can tolerate the FODMAP you are testing. Second, by conducting the test three days in a row and in increasing amounts, you can test your FODMAP threshold.

Your FODMAP threshold is the amount of FODMAPs you can have in your gut before you trigger symptoms. This threshold is different for everyone. By keeping a record of your reactions, you’ll get a better understanding of your personal limits.

To test a FODMAP: on day 1, test 1/4 of a normal serving; on day 2, test 1/2 a normal serving; and on day 3, test a full serving. If you need help choosing a test food, there is a list of options below.

Stop the test if you experience symptoms you wouldn’t tolerate in your daily life. These might include constipation, diarrhea, cramping, or excessive bloating, etc. Remember, mild bloating after eating and stools between 3-5 on the Bristol Stool Scale are considered normal digestion.

Cautious Systematic Re-Challenge

Cautious Systematic Testing Chart

If you had severe symptoms before you started the Low FODMAP Diet, you might want to try a cautious systematic re-challenge.

This process is similar to the classic systematic re-challenge, in that a single food is tested in increasing amounts. But, instead of rolling tests into one another, there’s a 24-hour break in between. This gives your body a break before adding more FODMAPs to your digestive system.

This is handy if you think you’ll have an aggressive reaction to a FODMAP group. You can still gather information on your personal FODMAP threshold. Just remember to keep notes on any symptoms.

The FODMAP Freestyle Re-Challenge 

The FODMAP Freestyle

The FODMAP freestyle is normally the third and final phase of the program. But, if you have mild or moderate symptoms you can use it to complete your re-challenge.

To use this system, eat a normal portion of your test food one time, followed by a 24-hour washout period. If you don’t have symptoms, you can add the food back to your long-term diet immediately.

It’s recommended you start with foods containing one FODMAP and work up to foods that have multiple FODMAPs. More on that later.

You should also focus on foods from one FODMAP group at a time. This will help you quickly identify problem groups. You can stop testing a group if you fail several individual tests. You don’t need to test foods you don’t want in your long-term diet.

Remember, if you have a mild to moderate reaction to a test food, you can always re-test a smaller portion. Your goal is to add as many foods to your diet as possible. This may include some half or quarter portions.


What Should You Test?

FODMAPs belong to 5 specific groups (fructose, lactose, fructans (FOS), galactooligosaccharides (GOS), and polyols). If you need a refresher on FODMAP groups, you can check out this article.

While there are recommended test foods for each group, the golden rule is to use food with only one FODMAP. This is important because if you react to food with more than one FODMAP, you won’t know which one caused your symptoms.

When you’re ready to test, you can use the suggestions below or pick food from your normal diet using the Monash app.


To test your tolerance to fructose, you can use: 100% pure honey, Coca-Cola containing High Fructose Corn Syrup (HFCS), mangos, or sugar snap peas.


To test your tolerance to lactose, you can use cows milk, sour cream, cream cheese, or yogurt.


Fructans are normally broken into two or more tests: 1) produce, 2) grains and cereals, and 3) inulin. Each of these subcategories has a different chemical structure, so your body may react differently when they’re digested. You should test produce and grains separately, at the very least.

Produce: To test this fructan chain, you can use grapefruit, raisins, onions, garlic, savoy cabbage, or the white part of a leek or spring onion.

Grains: To test this fructan chain, you can use white or whole wheat bread, wheat pasta, corn flakes, or Rice Krispies.

Inulin: To test this fructan chain, you can use gluten-free bread or baked goods containing inulin/chicory root (but no other high FODMAP ingredients).

Galactooligosaccharides (GOS)

To test your tolerance to galactooligosaccharides, you can use kidney beans, black beans, chickpeas, or almonds. If you test with beans, use dry beans and cook them yourself. Canned beans have a different FODMAP level.


Polyols include naturally occurring mannitol and sorbitol, as well as artificial sweeteners (normally ending in -ol). To test your tolerance to polyols, you can use pitted prunes, cauliflower, sweet potatoes, avocados, or artificially sweetened gum.

What Happens After Re-Challenge?

Once you’ve completed your re-challenges, you’re ready to start the third and final phase: reintroduction.

Using the information gathered during your re-challenge, pick a group you tolerated well. Make a list of all foods you want to add back in that group. Then, using the FODMAP freestyle method, test each food one at a time. Once you have tested a food, if you don’t react, you can leave it in your diet permanently.

When you’ve added back everything you can, you’ll have a Low FODMAP Diet designed specifically for you. It may need to be adjusted over time, but you can follow this modified diet long-term.

Final Thoughts

While it can be tempting to stay on the elimination diet forever, it can damage your gut bacteria. So, if you’re ready to move on to the re-challenge phase, you should make the transition as soon as possible.

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  1. Barrett, J., Dr., & C., (Dietitian, Ph.D. Candidate). (2015, June 8). Just 2-6 Weeks, it is not a STRICT diet for life [Web log post]. Retrieved from http://fodmapmonash.blogspot.ca/2015/06/just-2-6-weeks-it-is-not-diet-for-life_8.html
  2. Carabotti, M., Scirocco, A., Maselli, M. A., & Severi, C. (2015). The gut-brain axis: interactions between enteric microbiota, central and enteric nervous system. Annals of Gastroenterology, 28(2), 203-209. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4367209/.
  3. De Paula, J., Eliakim, R., Fedorak, R., Gangl, A., Garisch, J., Kaufmann, P., . . . Guarner, F. (2017, February). Probiotics and Prebiotics [PDF]. Milwaukee: World Gastroenterology Organization Global Guidelines.
  4. Distrutti, E., Monaldi, L., Ricci, P., & Fiorucci, S. (2016). Gut microbiota role in irritable bowel syndrome: New therapeutic strategies. World Journal of Gastroenterology, 21(22), 7th ser., 2219-2241. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4734998/.
  5. Goldman, B. (1970, January 13). Low-fiber diet may cause irreversible depletion of gut bacteria over generations. Retrieved from https://med.stanford.edu/news/all-news/2016/01/low-fiber-diet-may-cause-irreversible-depletion-of-gut-bacteria.html
  6. Makharia, A., Catassi, C., & Makharia, G. (2015). The Overlap between Irritable Bowel Syndrome and Non-Celiac Gluten Sensitivity: A Clinical Dilemma. Nutrients, 7(12), 10417-10426. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4690093/.
  7. Martin, L., MSc RD. (2016). Re-Challenging and Reintroducing FODMAPS A self-help guide to the entire reintroduction phase of the low FODMAP diet. Lexington, KY: Lee Martin.
  8. The Monash University low FODMAP diet: reducing poorly absorbed sugars to control gastrointestinal symptoms. (2013). Clayton, Vic.: Monash University.
  9. The Structured FODMAP Food Challenge [PDF]. (2014, January). St. Catharines: Niagara Health System.
  10. Rajilić-Stojanović, M., Jonkers, D. M., Salonen, A., Hanevik, K., Raes, J., Jalanka, J., . . . Penders, J. (2015). Intestinal Microbiota And Diet in IBS: Causes, Consequences, or Epiphenomena? The American Journal of Gastroenterology,110(2), 278-287. doi:10.1038/ajg.2014.427
  11. Staudacher, H. M., Lomer, M. C., Anderson, J. L., Barrett, J. S., Muir, J. G., Irving, P. M., & Whelan, K. (2012). Fermentable Carbohydrate Restriction Reduces Luminal Bifidobacteria and Gastrointestinal Symptoms in Patients with Irritable Bowel Syndrome. Journal of Nutrition, 142(8), 1510-1518. Retrieved from http://jn.nutrition.org/content/142/8/1510.full

© 2017 Amy Agur – The FODMAP Formula

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Leave a Comment

  • John

    You actually mentioned this wonderfully.

  • LowFODMAP_lover

    Hi Amy! Thanks for this much needed info! I have just started the low FODMAP diet and had been on the lookout of Low FODMAP food list ever since. Its been years!

    • Amy Agur

      Hi LowFODMAP_lover!

      This list isn’t exhaustive, but it’s a good place to start. The information comes from the Monash Low FODMAP Diet booklet, Re-challenging and Reintroducing FODMAPs by registered dietitian Lee Martin, and information I gathered directly from my dietitian. I always recommend discussing your re-challenge plan with your dietitian for the best results. Thank you for the feedback. I’m glad you found the list helpful!


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