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How To Complete the Re-Challenge Phase

Wondering how to complete the re-challenge phase of the Low FODMAP Diet? Check out this article for an explanation of why you need to re-challenge and how to get it done.

If you’ve completed 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 will likely trigger your symptoms at least once. Additionally, finding information on completing the re-challenge phase can be difficult.

So, in this article, I’ll discuss why you need to transition out of the elimination phase; how to complete the re-challenge; and what comes after. Hopefully, this information will help you move from the elimination phase to the re-challenge phase as smoothly as possible. Let’s get started!

Do You Really Need to Re-Challenge?

Though it can be tempting to stay in the elimination phase indefinitely, the Low FODMAP Diet is a diagnostic tool, not a long-term solution. In fact, research has shown that restricting high FODMAP foods can be dangerous for your gut health. Let me tell you why.

According to Monash University, Stanford University, and The Journal of Nutrition, long-term restriction of prebiotics (like many high FODMAP foods) have been linked with a reduction in good gut bacteria.

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

So, what does this have to do with you? The Journal of Nutrition has indicated within 4 weeks of starting the Low FODMAP Diet, patients show lower concentrations of “luminal bifidobacteria” in their digestive system. This particular bacteria is linked to changes in the immune system and abdominal pain.

Stanford Universtiy has also cautioned that loss of biodiversity in the gut 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 method 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 described in more detail below.

The process of testing is straight forward. Once your symptoms have subsided, select 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 important, as it allows time for the FODMAPs you consumed during testing to leave your system. This means you complete your next test in a “clean” environment. Failure to properly evacuate previous FODMAPs from your digestive tract may skew the results of your next test. So cutting your washout period short to save time is not recommended.

Additionally, with the exception of the food being tested, you will remain on the elimination diet for the duration of the re-challenge phase. Food from the groups you can tolerate will be reintegrated in the third and final phase of the program.

As an important side note, if you did not complete a daily food journal during the elimination phase, I highly recommend you start one now. This will help you determine if a food is safe, should be eliminated completely, or if a small amount can be tolerated on a day-to-day basis. You will also record important information on how long it takes you to react to each FODMAP and how you react specifically. If you need a template or more information on how to journal effectively, you can check out this article: 3 Reasons to Keep A Food Journal.

Finally, remember, according to Monash University, the Low FODMAP Diet is meant to be supervised by a FODMAP trained dietitian. If you have access to a medical professional who can supervise your Low FODMAP Diet, you should consult them prior to starting your re-challenge phase.

Classic Systematic Re-Challenge

Using this form of testing, a food containing one FODMAP is eaten in increasing amounts over a period of 3 days. This three-day testing schedule will provide 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 ingest before you experience symptoms. This threshold is different for everyone. Documenting your reactions will give you a better understanding of your personal limits.

Classic Systematic Testing
If you aren’t working with a dietitian, in order to test food in increasing amounts, pick one food containing one FODMAP (I suggest using the foods listed below or using the official Monash University app to select your food). On day 1, test 1/4 of a normal serving. On day 2, test 1/2 a normal serving. On day 3, test a full serving.

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

If you experienced severe symptoms prior to the Low FODMAP Diet, you and your healthcare team may opt for 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. The difference is, instead of rolling tests into one another, there is a break 24-hour break in between.

This method of testing lowers the pressure on your FODMAP threshold by allowing more time to elapse before introducing additional FODMAPs into your digestive tract. This is beneficial when you suspect you will have an aggressive reaction. Information can still be gathered on your personal FODMAP threshold by noting symptom changes as the volume of test food increases.

Cautious Systematic Testing Chart

The FODMAP Freestyle Re-Challenge 

If your symptoms are mild to moderate, or you have additional health conditions that mean you can’t complete the tests systematically, you can do the FODMAP freestyle. This is normally the third and final phase of the diet, in which every food removed is tested individually and reintegrated if possible.

To use this method, eat a normal portion of the test food one time, followed by a 24-hour washout period. If you tolerate the food, you can add it to your daily diet immediately.

The FODMAP Freestyle

It is normally recommended you start with foods containing one FODMAP and work up to foods that contain multiple FODMAPs. Also, focusing on one FODMAP group at a time will help you quickly identify problem groups. You can discontinue testing of a group if you fail several individual tests.

Since each food is only tested once, if you have a mild to moderate reaction, you can re-test a smaller portion of the same food after the 24-hour “washout” period.

What Should You Test?

As you may recall, FODMAPs are divided into 5 distinct groups (fructose, lactose, fructans, 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 foods containing only one FODMAP. This is important because if you react to a food containing more than one potential trigger, you won’t know which one caused your symptoms.

When you’re ready to test, either use the suggestions below or use your official Monash app to find foods that approximate your normal diet.


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 molecular chain length, so your body may react differently when they are ingested. You should at least test produce and grains separately.

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 content.


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 have completed your re-challenges, you are ready to start the third and final phase: reintroduction.

Using the information gathered during your re-challenge, pick a group – normally one you tolerated well – and make a list of all foods in that group you cut out during the elimination phase. Using the FODMAP freestyle method outlined above, test each food one at a time; working your way through the foods you removed during the elimination phase. 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 will have a long-term Low FODMAP Diet designed specifically for you. Though it may need to be adjusted as your body changes with age, you can follow this modified diet long-term.


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Did you like this article? You might also like one of these:

What is Irritable Bowel Syndrome?

What is a FODMAP?

Living on the Low FODMAP Diet

© 2017 Amy Agur – The FODMAP Formula







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  • John

    You actually mentioned this wonderfully.


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