If you are reading this blog, that probably means you have successfully finished the elimination phase of the low FODMAP diet. Congratulations!

Now we are ready to move on to a nicer part of the low FODMAP diet: the FODMAP reintroduction! A lot of people are a bit afraid of the reintroduction phase because they are scared that they will experience a lot of symptoms again.

And I fully understand that. But let’s try to look at it from the positive side: this phase is going to help you identify your food triggers and give you more of your freedom back around food. Isn’t that great?

In this article, I will give you all the information you need about the reintroduction phase, so you can do the tests successfully and find out your triggers. 

What is the reintroduction phase? 

The reintroduction phase is the second phase of the low FODMAP diet, also known as the challenge phase. The goal of this phase is to find out which FODMAP groups trigger your IBS symptoms.

You do this by testing / challenging the different FODMAP groups through food tests. 

As I have explained in this blog about the low FODMAP diet, there are 6 FODMAP groups: fructose, lactose, sorbitol, mannitol, fructans and galactans (GOS). In each test you test one of these groups.

Each test consists of 3 testing days and on every testing day you test a larger amount of a test food. During each test, you monitor your symptoms and like this, you will find out how you react to each of the FODMAP groups.

I always advise to monitor your symptoms by keeping a food- and symptom diary. 

At the end of the reintroduction phase, you will know which FODMAP groups you don’t tolerate, which you tolerate in small amounts and which groups you can eat freely.

After this phase you can start moderating the FODMAP diet to create your own personalised FODMAP diet with more food freedom. 

When are you ready to start reintroducing? 

You are ready to start the reintroduction phase if you have followed the elimination phase of the diet for 2 to 6 weeks and your symptoms are under control. This means that your IBS symptoms have been reduced to a minimum. 

Did you follow the elimination phase for 2 to 6 weeks, but do you still feel like you have too many symptoms to be able to start reintroducing? Then I advice to visit your dietician and look at how to proceed.

It is important that your symptoms have significantly decreased and that you have a mostly calm gut when you start the reintroduction phase.

Otherwise, it will be very hard to say whether the symptoms that you are experiencing come from the test food or from something else. 

There are several reasons why you still experience too many symptoms, even though you have been following the elimination phase. In this blog, I explain 5 reasons why the FODMAP diet might not be working for you yet.

One of the reasons can be that you still make some mistakes in following the FODMAP diet and eat higher amounts of FODMAPs than you think, which can cause symptoms or you might have another food intolerance beyond FODMAPs that causes symptoms.

The best way to find out why you still have symptoms is to consult with your dietician, eat strictly low FODMAP for a few more weeks and keep a food- and symptom diary, so you can work out with your dietician what the reason for your issues is.

If your gut has calmed down enough, you can proceed to the reintroduction phase.  

Is it necessary to reintroduce? 

A question I sometimes get is: “is it really necessary to do the reintroduction phase? I feel so good now that I have done the elimination phase and I have my symptoms under control.

I don’t want to mess that up by doing the reintroduction”. I understand very well that you feel this way, it is so much more comfortable to stay in the safety of the elimination phase.

But there are a few reasons why it is highly recommended to move through the challenges: 

• You will have more freedom: when you find out what your triggers are, you will have a lot more freedom in what to eat. Most people find out that they can tolerate several FODMAP groups and being able to add those back into your diet gives you a lot more food freedom.
  
  It will be easier to eat out, easier to enjoy meals at your friend’s and family’s houses. You will feel a lot less restricted and isolated. 
  
• It increases the variety of your diet: the low FODMAP diet is a very restrictive diet. If you stay in the elimination phase, you might be unnecessarily restricting yourself and keeping important nutrients from your body. 
  
• FODMAP-rich foods are important for your gut bacteria: some foods that are high in FODMAPs help the growth of good bacteria in your gut. These bacteria act like probiotics.
  
  Restricting FODMAP foods for too long can harm the variety of good gut bacteria in your gut, the health of your gut and your overall health. Therefore it is important to bring some high FODMAP foods back into your diet. 

Source: Monash FODMAP

How long does the reintroduction phase take?

Monash says the reintroduction phase is expected to take 6 to 8 weeks. I personally find that quite short. They recommend 9 different tests, more about that below and I think for most people each test will take about a week.

If you don’t get symptoms you can move on to the next test quicker. Sometimes the tests can take a bit longer, for example when you go through a stressful period and experience increased symptoms.

In such periods, it is better to pause testing because you cannot be sure that the symptoms you have are because of the stress that you are in or because of the food that you tested. 

How to do FODMAP reintroduction?

There are two ways to do the FODMAP reintroduction: 

Three testing days in a row

• Day 1: test day – small amount
• Day 2: test day – moderate amount
• Day 3: test day – large amount
• Day 4-6: rest day 

With this testing method, you do three testing days in a row. On the first day, you start with a small amount and you build this up to a large testing amount on day 3.

This is the testing method that Monash University advises because this will help you to move through the tests as quick as possible. The advise is to always take 2-3 rest days after the 3 test days.

If you have symptoms, wait until your stomach is calm again before you proceed to the next test, also if this takes more than 3 days. 

Source: Monash FODMAP

Three testing days with a rest day between each test

• Day 1: test day – small amount
• Day 2: rest day
• Day 3: test day – moderate amount
• Day 4: rest day 
• Day 5: test day – large amount
• Day 6-8: rest day

With the second method, you do one testing day and then a rest day. Another testing day and a rest day again etc. This way of testing takes a little longer, but there are reasons why you would prefer to test with method two:

• If you have constipation it can take longer for your symptoms to show. So in that situation, it can be better to have rest day between each test. 
• If it makes you feel more secure to have a rest day between each test
• If your dietician recommends this schedule or another testing schedule that he or she thinks better fits

Which foods to use for the tests? 

When picking testing foods it is important that these foods only contain one of the FODMAP groups.

Some foods contain a high amount of more than one FODMAP group and if you use one of those foods, you won’t know to which FODMAP group you react.

Therefore, pick foods that contain only one FODMAP. After you finish the reintroduction phase, you can start testing foods that contain more than one FODMAP. 

Be aware that the recommendations for which foods to use for each test have changed over the years.

There are still lists around on the internet that are old and the foods that are recommended there might not always be the best foods for testing a group.

For example, because the food has quite a high low FODMAP serving size or because the food contains more than one FODMAP.

I recommend using the amounts stated in the Monash University FODMAP app. Because the app is always up-to-date and the app is made by the creators of the FODMAP diet.  

You can find the recommended challenge foods by opening the app, clicking on the diary, clicking the plus on the upper right side, and then clicking the symbol with the apple and the arrow.

There you can select the FODMAP group and see which foods they recommend. Below I have listed a few options for each FODMAP group: 

Fructose

Pick one of the foods below to test. Test the following amounts on days 1, 2, and 3: 

• Honey: 1 1/2 tsp (10 g), 2 tsp (14 g), and 1 tbsp (28 g)
• Mango: 1/4 mango (52 g), 1/2 mango (104 g) and 1 mango (208 g)
• Orange juice: 2/3 cup (140 g), 3/4 cup (157 g), and 1 cup (201 g)

Lactose

Pick one of the foods below to test. Test the following amounts on days 1, 2, and 3: 

• Yogurt: 1/2 tub (85 g),  1 tub (170 g), and 1 cup (200 g)
• Milk: 1/4 cup (60 ml), 1/2 cup (125 ml), and 1 cup (250 ml)

Mannitol

Pick one of the foods below to test. Test the following amounts on days 1, 2, and 3: 

• Cauliflower: 2 small florets (17 g), 4 small florets (33 g), and 8 small florets (66 g)
• Sweet potato: 3/4 cup (105 g), 1 cup (140 g), and 1 1/2 cup (210 g)

Sorbitol

Pick one of the foods below to test. Test the following amounts on days 1, 2, and 3: 

• Avocado: 1/4 small avocado (40 g), 1/2 avocado (80 g) and 3/4 avocado (120 g)
• Blackberries: 2-3 berries (13 g), 5 berries (25 g), and 10 berries (50 g)

Fructans – garlic

Garlic is tested separately in the fructans test. Test garlic in the following amounts on days 1, 2, and 3: 

• Garlic: 1/4 clove, 1/2 clove, 1 whole clove

Fructans – onion

Onion is tested separately in the fructans test. Test one of these options on days 1, 2, and 3:

• Onion (red or white): 1/8 onion (11 g), 1/4 onion (22 g), and 1/2 onion (44 g)

Fructans – grain

Grains are tested separately in the fructans test. Test one of these options on days 1, 2, and 3: 

• Wholegrain wheat bread: 1 slice (26 g), 1 1/2 slices (39 g), and 2 slices (52 g)
• Wheat pasta: 2/3 cup (100 g), 1 cup (150 g), 1 1/2 cup (220 g)(cooked weight)

Fructans – vegetable and fruits

Monash also recommends testing a fructan vegetable or fruit. Test one of these options on days 1, 2, and 3:

• Raisins: 1 1/2 tbsp (19 g), 2 tbsp (26 g), and 3 tbsp (39 g)
• Grapefruit: 1/2 medium (104 g), 1 medium (207 g), and 1 large (280 g)
• Brussels sprouts: 3 sprouts (57 g), 4 sprouts (76 g), and 5 sprouts (95 g)

Galactans (GOS)

Pick one of the foods below to test. Test the following amounts on days 1, 2, and 3: 

• Almonds: 15 nuts, 20 nuts, and 30 nuts
• Canned chickpeas, rinsed: 1/2 cup (84 g), 2/3 cup (112 g), and 1 cup (168 g)

Which group should I test first? 

It doesn’t matter which group you test first. Most people start with the group that they are most curious about because they want to know if they can or cannot add that group back into their diet.

But there is no fixed order that you have to follow. 

How to make your reintroduction a success

Some tips that can help you move through the reintroduction phase smoothly:

• Make sure that you continue to eat strictly low FODMAP through the entire reintroduction phase. If you don’t do this, you can get symptoms and this might interfere with your test results. 
  
• Don’t add the FODMAP groups that you didn’t react to back into your diet until you have finished the reintroduction phase. 
  
• Keep a food- and symptom diary to track how you are reacting to the different tests and to know when you are ready for the next one. 
  
• Do the reintroduction phase under the guidance of a FODMAP-certified dietician, so you have somebody to help you interpret test results and symptoms. 
  
• Wait until your symptoms have settled before you start a new test. 

Frequently asked questions about the reintroduction phase

There are several questions that I often get asked about the reintroduction phase. I have bundled all of those questions and in this blog, FODMAP-certified dietician Manon te Linde answers all frequently asked questions about the reintroduction phase. So head over to that blog to get your questions answered. 

Some more helpful content

Looking for more information and tips for the low FODMAP diet? Also, check out these articles:

• 80+ low FODMAP snacks
• 100 tips for the FODMAP diet: everything you need to know
• The elimination phase

I hope this blog has helped you to navigate the reintroduction phase. Do you have more questions? Feel free to ask them below or to ask them in the Karlijn’s Kitchen Facebook community. A closed Facebook group where you can ask questions and share your experiences with other fodmappers.