How the FODMAP Diet Works – Step 1: The Elimination Phase

Published on: 01/12/2021

The FODMAP Elimination phase is what most people think of when they hear about the Low FODMAP diet. One of the most important concepts to understand about it is that it is not a long-term diet. It is a temporary learning process that allows people suffering from Irritable Bowel Syndrome (IBS) to identify the foods that trigger their symptoms. In this blog post, I will explain how it works, with a focus on the first step: the FODMAP elimination phase.

The FODMAP Elimination Phase: The First Step

To begin with, the low FODMAP diet is a 3-step process. The FODMAP elimination phase is only the first step. During this phase, you reduce your intake of FODMAPs with the goal of finding relief from IBS symptoms.

After that, once you feel better, you need to move on to the second step: the reintroduction phase. The “problem” foods vary considerably among individuals and there is a lot of detective work to do. By systematically re-challenging high-FODMAP foods, you can identify the specific foods you don’t tolerate. This knowledge about which foods to avoid or limit, and which ones to enjoy liberally, will allow you to create your personalized diet (step 3).

After all, the ultimate goal of this journey is to liberalize your diet to include as many foods as possible while maintaining good symptom control and improving your quality of life. To begin with, let’s discuss the key things you need to know about this first step.

5 Things to Know About the FODMAP Elimination Phase

1. It’s more about replacing than eliminating

Although the name elimination may invoke ideas of a very restrictive diet, this diet doesn’t exclude any food group. This is unlike more restrictive diets out there that eliminate all carbohydrates or grains, legumes, gluten, or dairy. In fact, I like to think of the FODMAP elimination more as a “replacement” phase. You replace high-FODMAP vegetables, fruits, grains, dairy products, and nuts/seeds, with their low-FODMAP counterpart.

Undoubtedly, you will need to eliminate a few foods altogether, like the infamous garlic and onions. Nevertheless, those are few and you still have a variety of choices in all food groups. In addition, for many high-FODMAP foods, there is a low-FODMAP amount. We are not trying to achieve a “zero” FODMAP intake, just to lower the overall load of FODMAPs.

2. What foods need to be restricted in the FODMAP elimination phase?

The term FODMAP was coined by researchers at Monash University, where this protocol was formulated. FODMAP stands for Fermentable Oligo- Di- Mono-saccharides And Polyols. These are certain carbohydrates that are poorly absorbed or not absorbed at all. As a result, they may lead to symptoms of bloating, excessive flatulence, abdominal pain, either constipation or diarrhea, or a mixture of both. These carbohydrates fall into four main groups:

  • Lactose: milk, yogurt, and ice cream
  • Excess Fructose: certain fruits, high-fructose corn syrup, honey, agave
  • Polyols/sugar alcohols: certain fruits and vegetables like blackberries and cauliflower, and some sugar-free foods (candy, gums)
  • Oligosaccharides: types of fiber in wheat, onions, garlic, beans, nuts, and soy milk

3. The goal is to achieve adequate symptom relief

The goal of the FODMAP elimination phase is to reduce high-FODMAP foods until symptoms have been reduced considerably, if not entirely eliminated. Research has shown that it takes 2-6 weeks for people to experience adequate symptom relief. Once your symptoms have improved, you should move on to the next phase. There is no need to stay in the elimination phase longer.

4. The FODMAP elimination phase is temporary

It is important to remember that this is only a temporary phase, as it limits many nutritious foods. If not well planned, a low FODMAP diet can be low in certain key nutrients, mostly calcium, and dietary fiber.  If the diet is implemented correctly – ideally with the help of a dietitian specialized in this field – and symptoms do not improve after 6 weeks, there is no reason to continue. You should go back to your usual diet and seek the advice of a medical professional to investigate the reason for your symptoms. There are other non-diet therapies that can help.

5. This phase shouldn’t be more restrictive than it needs to

There is a tendency to be wary of all fiber-rich foods and eliminate them altogether during the FODMAP elimination phase. But fiber is key to having regular bowel movements. Therefore, it is important to include low FODMAP sources of fiber. Some examples are whole grains (brown rice, quinoa, millet), and low-FODMAP vegetables, fruits, and legumes.

Similarly, many people think they need to avoid gluten or dairy completely. But this is not true! In fact, this can lead to unnecessary restrictions and poor intake of calcium, B vitamins, and fiber. You can include some gluten-containing foods like sourdough bread. And, unless you are vegan or are allergic to dairy, you can have lactose-free sources of dairy, such as lactose-free milk or yogurt and some hard cheeses, which are naturally low in lactose.

In summary, the FODMAP elimination phase is the first of three steps to complete that will allow you to figure out your triggers and expand your diet without experiencing IBS symptoms. If you are ready to start, seek the help of a trained dietitian (like me) to help you get through all the phases of the low FODMAP diet accurately and efficiently, and maximize your success!

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I’m a registered dietitian with a passion for helping women with IBS find their way back to eating without fear of painful gut symptoms and without unnecessary diet restrictions.

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