How to Follow an Elimination Diet for IBS

An elimination diet is a tool to use to assess whether specific foods are contributing to your irritable bowel syndrome (IBS) symptoms. This is not a "diet" in the traditional sense, but a way to systematically find out if certain foods are causing symptoms in your body.

Why Use an Elimination Diet for IBS?

An elimination diet can be a helpful strategy to learn more about your IBS. Reasons people try elimination diets include the following:

• To identify specific food triggers. In this case, you would be using an elimination diet to pinpoint a specific trigger food. Foods that are known to trigger IBS include:
  • Dairy products
  • Gluten-containing foods (wheat, rye, barley)
  • Corn
  • Soy
• As part of the low-FODMAP diet for IBS. FODMAPs (fermentable oligosaccharides, disaccharides, monosaccharides, and polyols) are short-chain carbohydrates that some people have difficulty absorbing—which causes digestive symptoms. The initial phase of the low-FODMAP diet involves eliminating all high-FODMAP foods for a period of two to eight weeks.

Before You Start

There are a few things you can do before starting an elimination diet that can help you maximize the benefits of this difficult treatment plan. Consider taking the following steps:

Talk to your healthcare provider about getting tested for celiac disease

Whether you choose to eliminate gluten from your diet because you suspect you have a gluten sensitivity or because you are planning to follow the restrictions of the low-FODMAP diet, you should get tested for celiac disease first.

IBS and celiac disease share many symptoms. People who have IBS are at higher risk of having undiagnosed celiac disease, an autoimmune condition marked by an intolerance to gluten. 

It's important to get tested before starting your diet because the blood test for celiac disease is only accurate if you are still eating gluten at the time of the testing.

Start a food diary

Whether you use a simple notebook or an online tracking app, it is very helpful to keep a running account of what foods you are eating, what your symptoms are, and any other factors (e.g. stress level, menstrual cycle) that may be contributing to your symptoms.

Decide what foods to eliminate

If you choose to follow the low-FODMAP diet, you will be eliminating—at the very least—all high-FODMAP foods. During the initial elimination phase, many people eliminate the following foods:

• Dairy products
• Food and drinks containing wheat, barley, and rye
• Beans, lentils, nuts, legumes, and seeds
• Vegetables
• Fruits
• High-fat foods
• Processed foods
• Anything with additives or preservatives
• Coffee, tea, and soda
• Alcohol

Stock your kitchen

Elimination diets require you to pay close attention to what foods you are eating. You may find it easier to cook and prepare most of your meals at home so that you have full control over the ingredients. You will also want to make sure that you have plenty of options for breakfast, lunch, dinner, and snacks that do not contain the foods or ingredients that you are eliminating.

The Elimination Phase

During the first phase of your elimination diet, which will last around two weeks, you will stop eating all high-FODMAP foods (and any other suspected trigger foods). Think of this phase as a cleanse. It gives your digestive system some time to heal and may even help promote a healthy mix of gut bacteria.

During the first phase of the diet, it is important to chart your symptoms in your food diary. If you notice a significant reduction in symptoms, it means the elimination diet is working. Charting your symptoms, or lack thereof, helps you compare how different you feel during this time.

How long you need to stay in the elimination phase will depend on how you are feeling and how old you are. This diet is intended to be temporary. Many of the foods you will exclude are an important part of a healthy diet.

Everyone attempting an elimination diet should work with a licensed dietitian to make sure they aren't harming themselves. Children are particularly vulnerable to malnourishment, so you should never start your child on an elimination diet without first discussing it with their pediatrician.

The Reintroduction Phase

At the end of the elimination period, you will slowly reintroduce foods back into your diet, one at a time. If you are on the low-FODMAP diet, you could introduce foods one FODMAP type at a time.

On the first day, eat a small amount of the food or FODMAP type in question. If no symptoms occur, eat twice as much of the same food the next day. If you still have no symptoms, eat twice as much on day three as you did on day two. Pay close attention to any symptoms and document them in your food diary.

If you experience symptoms, then you have identified a trigger food that you may want to avoid in the future. If you haven't experienced symptoms, that food is probably safe. Still, you will need to remove the food from your diet again while you continue testing new foods, one at a time.

If you are following the low-FODMAP diet, after reintroducing and assessing tolerance for the first FODMAP type, you would then reintroduce other FODMAP types, one at a time.

The Goal of an Elimination Diet

Elimination diets are to be used as a tool for identifying foods that contribute to your IBS symptoms. The ultimate goal is to use this information to create a diet including as wide a variety of foods as possible without experiencing excessive symptoms. This will ensure that you are maximizing your intake of essential nutrients.

As you gather more information about your body's reactivity or tolerance to certain foods or FODMAP types, you may want to play around with portion size. You may find that your body can tolerate certain foods in small portions, but has more trouble with larger portions. This information will not only expand the variety of foods you can consume but may allow you to enjoy some of your old food favorites.