What is involved with the challenge/ re-introduction phase of the Low FODMAP Diet?


Last week we introduced what the low FODMAP diet is, and what you can expect during the elimination phase.  If you missed our last two posts on what is IBS and the elimination phase, please refer to the following blogs:

To read about the low FODMAP diet and Phase 1: Elimination phase:


To read about what IBS is:


The Low FODMAP Diet Consists Of Three Phases. The Three Phases Are:

Phase 1: Elimination

Phase 2: Challenge & Reintroduction

Phase 3: Maintenance 

This week, we will discuss Phase 2: Challenge/Re-introduction, why it is important to re-challenge foods, and how to do so.


So What Is Phase 2 – Challenge/Re-introduction?


The re-challenging phase is required to establish individual tolerance levels to subgroups in the low FODMAP diet.

To refresh your memory, FODMAP stands for Fermentable Oligosaccharides, Disaccharides, Monosaccharides and Polyols.


It is not recommended to remain on a strict low FODMAP diet long-term as it can be restrictive and often lead to nutrient deficiencies (particularly in iron, calcium and prebiotics) as well as social isolation. The aim of the re-introduction phase is to increase the variety of foods in your diet and nutritional adequacy through identifying, which subgroups are better tolerated and which subgroups trigger severe symptoms per patient.

Finding the perfect balance between symptom relief and expanding the variety of foods in your diet is the over-arching goal of the second phase.

The reintroduction phase is important, as limiting intake of prebiotics, which are found in some FODMAP foods, can lead to negative changes in the gut microbiome. It is strongly suggested to embark on the challenge/re-introduction phase with a dietitian to ensure that it is conducted accurately and with the correct serving sizes to identify appropriate tolerance levels. A dietitian will also highlight how to practically maintain your moderate FODMAP restriction, being phase 3, the maintenance phase. We will cover the maintenance phase next week so stay tuned for that post! If you have IBS and want to establish your triggers, you can find a make an appointment with us here: http://www.fodmapdietetics.com/contact-us/

When Should I Start Phase 2: Challenge/Re-Introduction?

The reintroduction phase generally conducted at the 3-4 week mark, once symptom relief has been established on the low FODMAP diet. It is important to note that if symptom relief was not experienced after 3-4 weeks of the elimination phase, there is no need to proceed to phase 2 or continue on a low FODMAP diet. The low FODMAP diet has success in up to 68-76% of individuals with IBS however, there is a small percentage of IBS suffers who may not benefit from the low FODMAP diet. If you are not experiencing any symptom relief after the elimination phase of the low FODMAP diet, it is recommended to see a dietitian to explore other options on how to manage your IBS.

What Are The Steps Of Re-Introducing FODMAP Containing Foods?

During the re-introduction phase, patients remain on a low FODMAP diet, whilst re-introducing one subgroup FODMAP at a time. The suggested foods for reintroduction are based on specific serving sizes and should only contain one type of FODMAP subgroup. For example, honey is high in fructose (in excess of glucose) but is not high in any other FODMAP group (like lactose, fructans, GOS, sorbitol, mannitol) and therefore is a good testing food for the FODMAP subgroup of fructose. Apples on the other hand, are high in both fructose and sorbitol, and therefore would not be a clear test for fructose as reactions may be a result of the high sorbitol content.

The re-challenge of each FODMAP subgroup generally occurs over 3 doses. The first dose being a moderate FODMAP serve, the second dose being a high FODMAP serve and the third being a very high FODMAP serve. These specific serving sizes will help your dietitian identify what quantities, if any, your body can tolerate and can use these doses to create a modified low FODMAP diet specific to your tolerance levels.


Examples Of Re-Challenge Foods For Each FODMAP Subgroup Include:

FODMAP Subgroup Example of Test Food Challenge
Test Dose 1 Test Dose 2 Test Dose 3
Fructose Honey 1 teaspoon 2 teaspoons 1 tablespoon
Lactose Cow’s Milk 125ml 250ml 375ml
Fructans  (wheat) Wheat bread 1 slice 2 slices 3 slices
Fructan (onion) Onion Cook whole onion in a meal remove whole pieces before eating 1 tablespoon chopped onion 2 tablespoons chopped onion
Fructan (garlic) Garlic Cook whole garlic in a meal remove whole pieces before eating ½ clove or 1 teaspoon minced garlic 1 clove or 2 teaspoons minced garlic
GOS Chickpeas 1/2 cup 3/4 cup 1 cup
Polyols (sorbitol) Sugar free mints 2 pieces 5 pieces 10 pieces
½ cup sliced ¾ cup sliced 1 cup sliced

*Please note that there are many other test foods that you can use to challenge FODMAP subgroups. Consult your dietitian to find your preference of appropriate challenge foods.


Challenge foods don’t have to be eaten alone (unless you want to)! The sound of eating a teaspoon of minced garlic may not be everyone’s cup of tea. So adding the challenge food to a meal you would normally eat, for example, your favourite low FODMAP stir-fry dish, is a good way to test your tolerance to foods.

Challenging the higher doses of FODMAPs can be difficult and often unrealistic, (e.g. 10 sugar free mints in a day!). Your dietitian can help you layer multiple small doses of the same FODMAP subgroup to help you test your tolerance at higher doses.

Keep A Food And Symptom Diary


Patients should monitor their symptoms as the foods are reintroduced, including the time they experience it. IBS symptoms can occur many hours after or even the following day, keeping a symptom and food diary can help your dietitian decipher which foods trigger your symptoms and what your tolerance levels are to specific serving sizes. Testing of each FODMAP should be done with a 2-3 day “washout” period in between each test, to ensure there is no overlapping of potentially triggering foods. This will ensure that the food that is tested is definitely well, moderately or not well tolerated.

If the challenge of a specific FODMAP subgroup is well tolerated and no symptoms occur, the food FODMAP subgroup can be completely reintroduced into the patients diet. Foods that cause a mild reaction can be reintroduced in smaller servings, and are better suited for when the patient is at home in case symptoms of discomfort are triggered. Foods that trigger severe symptoms should be avoided when creating their individual maintenance FODMAP diet. It is also important to note that normal symptoms of digestion commonly occur after ingesting FODMAP foods, such as minor bloating or flatulence, and should not be confused with severe IBS symptoms.

Now That I’ve Challenged All FODMAP Groups – What’s Next?

Once every subgroup FODMAP has been tested, dietitians will create an individual, modified low FODMAP diet based on your tolerance levels to each subgroup. If a food is poorly tolerated during this challenge phase, it does not mean it will always be poorly tolerated. It is important to re-challenge foods at a later time to further increase the variety in an individual’s diet, particularly if the food contains prebiotics to promote good gut health.

The re-challenging phase is crucial to improving the variety of foods allowed in your modified low FODMAP diet. Remaining on a strict low FODMAP diet can cause long-term nutrient deficiencies. Make sure you are working with a dietitian to ensure you are reintroducing the correct foods at the suggested portions in order to establish your individual tolerance levels.

Stay tuned for next week’s blog post on the phase 3 of the low FODMAP diet called the Maintenance phase!

Until next time,

Good Eating!

Written by: Charmaine Duong (APD, AN)

Edited By: Atlanta Miall-Shorten (APD,AN, AccSD)


Tuck C, Barrett J. Re-challenging FODMAPs: the low FODMAP diet phase two. Journal of Gastroenterology and Hepatology 2017 32(1):11-15.

Staudacher HM et al. Fermentable carbohydrate restriction reduces luminal bifidobacteria and gastrointestinal symptoms in patients with irritable bowel syndrome. J. Nutr. 2012; 142:1510-8.

Leech J. Diet Vs. Disease. FODMAP Reintroduction Plan and Challenge Phase: Your Guide and FAQ.  [Internet] [Updated 2018 Feb 25; cited 2018 Apr 16]. Available from: https://www.dietvsdisease.org/fodmap-reintroduction-challenge-plan/

 Everyday Nutrition FODMAP Friendly Challenge Handbook 2018 edition [Ebook]. Available from: http://www.everydaynutrition.com.au/store/p39/FODMAP_Friendly_Challenge_Handbook.html

What is involved with the challenge/ re-introduction phase of the Low FODMAP Diet?
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