Mastering the FODMAP Reintroduction Phase for a Healthier Gut

Before we discuss FODMAP reintroduction, let’s talk about the low FODMAP diet. The low FODMAP diet is a structured eating plan designed to help manage digestive symptoms like bloating, gas, and diarrhea, often associated with conditions like irritable bowel syndrome (IBS). The low FODMAP diet has also shown promise in digestive conditions such as SIBO, inflammatory bowel disease, and endometriosis.

FODMAP stands for Fermentable, Oligosaccharides, Disaccharides, Monosaccharides, and Polyols—a group of short-chain carbohydrates (sugars) that are poorly absorbed in the small intestine. The poor absorption of these carbohydrates is what leads to the unpleasant digestive symptoms such as gas, bloating, distention, and change in bowel habits such as diarrhea.

The low FODMAP diet is divided into 3 phases that are overseen by a registered dietitian.

1. Elimination phase: Avoidance of high FODMAP foods for 2-8 weeks depending on how long it takes for symptoms to resolve.
2. Reintroduction/challenge phase: Begin trialing one FODMAP group at a time to determine which groups contribute to your symptoms. Typically, there are 1-2 groups that are particularly troublesome rather than all of the groups. This information will be utilized in the personalization phase! This phase can take anywhere from 8-12 weeks.
3. Personalization: This is the creation of a long-term eating plan that includes the FODMAP groups that were well tolerated during the challenges. The goal here is to have the least restrictive diet as possible therefore allowing for more nutritious options. This phase is ongoing!

The purpose of this blog is to discuss the details of the reintroduction/challenge phase of the diet.

Why Do We Do a Reintroduction Phase?

Hopefully if you’re reading this, your digestive symptoms are well managed after embarking on the elimination phase of the low FODMAP diet! The reintroduction/challenge phase can feel daunting and confusing, but as registered dietitians, we are here to make the process less stressful for you!

There are reasons why this step is so vital and shouldn’t be skipped over, which unfortunately I see quite often in practice where someone has been on the low FODMAP diet for a year or more!!

So, what exactly is the point of this phase?

• To identify the FODMAP groups that trigger symptoms. It is rare that every FODMAP group is going to bother an IBS individual, so we need to figure out which are the most troublesome for YOU. Either you tolerate it in large servings, moderate, or low servings. We then utilize this information to build a diet for you when the reintroduction phase is completed.
• To expand your food choices and support gut microbiome. Not only is an increase variety a goal, but consuming a diet that is devoid of adequate fiber and prebiotic rich foods (many FODMAP’s) is harmful to your gut microbiome diversity if done for too long. The importance of the gut microbiome cannot be forgotten when it comes to digestive conditions.
• To Improve quality of life. The elimination phase can have a significant impact on quality of life specifically, social experiences such as eating out. Many people feel they cannot safely eat out at many restaurants or adequately explain their dietary avoidances to their friends and family. The challenge phase serves as a solution for this to reduce anxiety around food in the long term. We want you to have the least restrictive diet as possible!

How to Start the FODMAP Reintroduction Phase

Preparation

The best thing you can do to prepare for this process is to work with a registered dietitian that specializes in this area! We can help to reduce confusion and provide structured guidance on the next steps. You will likely be asked to keep a food log with digestive symptoms so we can determine your level of tolerance to each food throughout the challenge phase so be prepared for that!

I also suggest looking ahead at your schedule each week to make sure you time your challenges to not interrupt trips, meetings, special events, etc in case symptoms do occur. You will remain low FODMAP through this whole process with the challenges intertwined within which is why I suggest getting comfortable/creative with the diet given this process can take up to 12 weeks!

Choose a Structured Plan

The structure for the FODMAP challenges that I utilize is a 3 day in a row challenge where you increase the portion sizes of a single FODMAP food each day. The 3 days will correlate with low, moderate, and high FODMAP portions that will be provided by your dietitian. If at any point during the 3 day challenge your digestive symptoms are moderate/severe, do not move to the portion size higher and your challenge will end.

After the 3 days, you remove the challenged food and resume your low FODMAP diet until symptoms subside. This is called the washout period which lasts 3-4 days meaning each challenge will last about a week. Once symptoms subside, it’s onto the next group! I typically let the client select which food they would like to try from the individual groups based on preferences, accessibility etc.

Below are the 5 FODMAP groups and sample foods that can be used for challenges. All of them contain only a single FODMAP for more accurate results.

Let’s say we want to start with the fructose group and honey is selected.

• Day 1—1 tsp honey. If no symptoms, move onto the second portion
• Day 2—2 tsp honey. If no symptoms, move onto the final portion
• Day 3—1 tbsp honey
• Day 4-7 is the washout period. Honey is stopped and back to the low FODMAP diet until the next challenge food

It’s also important to know that you do not need to eat these challenge foods alone! They can be added to a low FODMAP meal that has been safe for you throughout this process since only one thing could be the culprit!

Tips For Success During Reintroduction

• Introduce FODMAPs when you’re feeling well (avoid testing during stressful times or illness). It is sometimes advised to try and test foods during the week when you are less likely to eat out of the house and have social events to attend! For example, your 3 challenge days can be Mon-Wednesday and then you can start your washout.
• Be patient—some foods may require repeated trials.
• Continue with your meal structure you have employed during the low FODMAP elimination phase. There’s no reason to re-invent the wheel now so if you usually meal prep in bulk, keep up with that!
• Continue with adequate hydration, good sleep quality, and stress management.
• Keep a food log so your dietitian can review the challenges with you. This would include symptom tracking so we can distinguish between FODMAP reactions or a normal reaction. I typically have client’s food log with symptoms on our electronic app to make this process seamless. Some prefer hard copies so there are sample templates we can provide for hand written tracking.

What Happens After Reintroduction?

After the reintroduction/challenge phase is completed, we move onto step 3 which is the maintenance phase! All of the information that has been gleaned from the systematic challenges is used to build your long-term diet that will include the foods you tolerated well, and limits the foods you didn’t tolerate well.

This phase is much less structured than the challenge phase which can feel daunting. I typically suggest adding in your well tolerated groups in a way that reflects how your diet/routine looked previously. I still utilize food logging in the beginning of this phase because we don’t know how many well tolerated FODMAP’s you can consume in a meal or over the period of the day. For instance, let’s say you tolerated the fructan at the highest amount. We do not yet know if you can consume garlic, onion, and wheat (3 different fructans) in large amounts at the same meal or even multiple times throughout the day. So, there is still some experimentation to be had!

Ongoing Monitoring

If you happened to react to some of your favorite foods, do not fret! Tolerance to FODMAP’s can change over time with the turnover of your gut microbiome, so I suggested revisiting foods from time to time.

As you can see, the reintroduction/challenge phase of the low FODMAP diet is essential for many reasons. The top reasons being quality of life, gut microbiome diversity, and basic nutrient goals that need to be met with a variety of vitamins, minerals, and macronutrients. This process is lengthy, so setting time expectations in the first session is vital for continued compliance and success for the client! Practicing patience and curiosity during these challenges will help your dietitian to devise your long-term diet plan WITH you to the best of their ability.

FAQs about FODMAP Reintroduction

“What if I react to everything?”

If you react to everything, first I would take a look at your challenges to see if any other FODMAP foods were consumed at the same other. Other variables such as constipation may have skewed your results due to the slowed transit and backed up stool that can contribute to gas. If everything looks good here, I then consider the possibility of another digestive conditions. Specifically, small intestinal bacterial overgrowth (SIBO), as the migration of bacteria to the small bowel can cause FODMAPs to be fermented and lead to symptoms. This can be ruled out with a breath test or endoscopy culture through your gastrointestinal doctor, or some dietitians can order a breath test through a 3 rd party company!

“Can I skip reintroduction?”

I do not suggest skipping the reintroduction/challenge phase for the reasons mentioned above—-The depletion of good gut bacteria, poor nutrition related quality of life, and missing nutrients.

“Do I have to eat the challenge food alone?”

No, you do not! The challenge food is meant to be incorporated to any safe low FODMAP meal that you know that tolerate well. For example, you can add honey to lactose or dairy free yogurt, oatmeal, or a slice of sourdough toast with peanut butter.

“If I have a bad reaction to the moderate portion size, do I still do the largest portion challenge?”

No! If your reaction to any FODMAP food is severe, you will stop your challenge there. Reacting to the moderate portion guarantees the large portion will be a problem too since FODMAPs are dose dependent.

“If I tolerate the food, can I add the food back in immediately?”

Unfortunately, no. You cannot add in the FODMAP group trialed until finishing all of the challenges. This is because if you have a high fodmap food the same day as the next challenge food, it could skew your challenge results since reactions to FODMAP foods can be anywhere between 2-8 hours!

“What if I can’t eat the food suggested to be used for the challenge?”

Each group of the FODMAP’s have a few viable options for which food we can use to allow for alternatives. We will make this selection together to account for preferences!

Resources for FODMAP Reintroduction

Recipes:

• Rebecca Bitzer and Associates recipes and blogs
• Fodmap Everyday—large collection of recipes and ability to filter by FODMAP tolerance in later stages of the diet
• Monash University
• FODMAP Friendly

Food logging

• There are many electronic forms of food logging that can be used during this process, but each dietitian has their preference. We use the Nourishly application, but there are apps such as the symptom tracker. There are also tracking options through the Monash University app.