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Reintroducing FODMAPs [Dietitian’s Guide]

A Low FODMAP diet is not a long-term diet. The first phase is the elimination phase. The second phase includes reintroducing FODMAPs back into the diet one by one, in order to determine which ones are triggers for you. 

When the time comes to reintroduce foods, you may feel overwhelmed and be looking for some guidance. 

If this is you, you’re in the right place!

As a dietitian with lot’s of knowledge on this topic, I am here to help you understand how FODMAP reintroduction works. 

In this article, I will provide an overview of the low FODMAP diet, explain when and how to reintroduce FODMAP foods, and let you know what to expect once you add them back in. 

Here we go!

Overview of Low FODMAP Diet

The low FODMAP diet gets its name from the carbohydrates that are restricted: fermentable oligosaccharides, disaccharides, monosaccharides and polyols are short-chain carbohydrates that are avoided on a low FODMAP diet. This is due to their poor absorption rate, which allows them to sit and ferment in the colon, causing various symptoms of digestive distress (1). 

Some common foods that are high in FODMAPs include grains, dairy-based milk and yogurts and a variety of fruits and vegetables. 

When to go on a Low FODMAP Diet

A low FODMAP diet is beneficial for individuals who suffer from the following:

  • Dysbiosis– imbalance in the gut microflora 
  • Irritable bowel syndrome (IBS) 
  • Small intestinal bacterial overgrowth (SIBO) 
  • Acid reflux
  • Abdominal pain

The carbohydrates in FODMAPs can cause symptoms for individuals with the above conditions for 2 reasons: 1. Their presence in the gut draws more fluid into the gut via osmotic pressure and 2. The fermentation of these carbohydrates produces gas. These are natural occurrences that are present in all individuals, but trigger symptoms in those who are sensitive to FODMAPs.

Potential Deficiencies

The low FODMAP diet predominantly limits fruits, vegetables, grains and legumes. These foods are rich in dietary fiber, vitamins, minerals, phytonutrients, making them cornerstones of a healthy diet. For this reason, guidance from a dietitian is highly recommended throughout the process. Let’s take a look at these potential deficiencies.

Dietary Fiber

With such restrictions, it is easy to slip into an inadequate intake of fiber while on the low FODMAP diet. Fiber is important for digestive health, bowel regularity, and can help manage conditions such as diabetes and high cholesterol. You can boost your fiber intake by consuming  low FODMAP sources of fiber such as brown rice, oranges, kiwis, chia seeds and quinoa. Fiber supplementation may also be beneficial for some. 

Micronutrients & Phytonutrients

In addition, low FODMAP diets can easily be deficient in vitamins, minerals, and phytonutrients. These nutrients are essential energy metabolism, digestion, disease prevention, and overall wellness. In order to ensure adequate intake of these nutrients, eat fruits and vegetables from all the color categories, including: red, yellow, orange, blue/purple, white, and green. Reintroducing FODMAPs within 2-6 weeks of starting the diet is important in preventing nutritional deficiencies.

When To Reintroduce FODMAP Foods

Improved Symptoms 

After you have been following the diet for 3-6 weeks and see significant improvement in your symptoms, you are ready to start reintroducing FODMAP foods! This is the right time to initiate part two of this elimination diet.

Adequate Time 

In order to slowly add foods back in and determine your triggers, you’ll need a sufficient amount of time dedicated to preparing foods and logging intake and symptoms. Each time you introduce a new food you will have to be aware and conscious of how you are feeling throughout the days following, notifying you if this is an OK food for you or not. Therefore, it is not a good time to initiate the reintroduction phase if you are distracted.   

When to Discontinue Low FODMAP Diet

If no symptom improvements are seen after 4-6 weeks, it’s time to discontinue the diet and move on to another method of determining what is causing you discomfort. If you are following the diet correctly and symptoms don’t approve, FODMAPs probably aren’t the issue for you.

Reintroducing FODMAPs

The following are the general guidelines you want to stick to while reintroducing FODMAPs. Instead of feeling overwhelmed, do all your preparation in advance and go in knowing what to expect!

  1. Add one FODMAP category at a time– you want to isolate each category you are adding in, so you can easily know if that FODMAP is causing you symptoms or not. 
  1. Increase the portions as you go– start with a small portion on day 1. If you don’t feel any symptoms, double the portion on day 2. If you continue to not experience symptoms, double days 2’s portion on day 3. 
  1. Keep a 6 day cycle for each food– 3 days adding it back in and determining if it causes you symptoms or not and a 3 day washout period before challenging the next food. This gives you enough time to test out each food and keeps you from having food crossover before moving on to the next one. 
  1. Keep a food log– be mindful of how each food makes you feel over the 6 day cycle. Log down serving size consumed and symptoms that arise throughout the day. This will allow you to keep track of which foods are ok and in what amount. Additionally, it will allow you to remember what to discuss with a dietitian or doctor guiding you.  

What to Expect

When reintroducing FODMAPs your gut should be calm and you’ll probably be feeling better than you have in a while. 

This may scare you off from initiating the trial phase, but it’s a necessary step in order to allow foods that do not cause you harm back into your diet. This framework will allow you to identify which FODMAP category triggers symptoms and what amounts of each category you can tolerate. In doing so you will have increased food freedom, variety and nutrient intake.

During the reintroduction process you will have periods in which your original symptoms come back- this is your body notifying you that this food is not good for you. Therefore, you will probably have points of discomfort throughout this phase. For this reason, I recommend reintroducing foods when you are in a calm phase of your life and can afford to be feeling less than for a few days. 

This process allows trigger foods to be identified. Once those specific foods are eliminated, individuals can go back to eating everything else and not suffer from unpleasant symptoms.  


Reintroducing FODMAPs during the second phase of this diet can leave you feeling anxious and sometimes confused. With the right guidance and tips, you should be able to execute it, identify your triggers and return to a more normal diet. Remember, the low FODMAP diet is not a forever diet. The elimination phase should be kept to 2-6 weeks to avoid nutritional deficiencies. If you need help, seek out a registered dietitian with experience guiding patients through this diet. You don’t have to do it alone!

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