The Basics of The Low FODMAP Diet (PDF)

Author: Patsy Catsos, MS, RDN 


Patsy Catsos

About the Author: Patsy Catsos, MS, RDN is a medical nutrition therapist, FODMAP expert, and author. The focus of her practice is digestive health, including irritable bowel syndrome, gluten-related disorders, and inflammatory bowel disease. Patsy completed her undergraduate studies at Cornell University and earned a Master’s degree in Nutrition at Boston University; she interned at Boston’s Beth Israel Hospital. She is the 2020 recipient of the Academy of Nutrition and Dietetics’ Excellence in Clinical Practice Award. Patsy wrote IBS—Free at Last!, her first book, in 2008 and it introduced the FODMAP approach to many thousands of IBS patients, dietitians and physicians. The latest edition of her book is The IBS Elimination Diet and Cookbook (Harmony Books, 2017). Patsy is a professional member of the Crohn's and Colitis Foundation. She is an Associate Member of the American College of Gastroenterology, where she serves as a nutrition expert in the ACG Functional GI Health and Nutrition Circle. 


The Basics of the Low FODMAP Diet (PDF) 

Low FODMAP diets are often recommended by healthcare providers for people with irritable bowel syndrome (IBS). If you are looking for help getting started, you have come to the right place. It will be easier for you once you understand the basics of the low FODMAP diet. In this article we’ll make sure you understand the basics, and we’ll share a handy low FODMAP diet PDF with you, too. 

What are FODMAPs? 

FODMAPs are a group of sugars and fibers found in food that can trigger irritable bowel syndrome symptoms in up to 85% of people with IBS. FODMAPs are often found in what we would otherwise think of as healthy foods, especially when they are eaten in large portions. So, the basics of the Low FODMAP diet are more complicated than for most other diets that just talk about good foods and bad foods. [FODMAP is an acronym that stand for Fermentable, Oligosaccharides, Disaccharides, Monosaccharides and Polyols. Specific FODMAPs include fructose, lactose, mannitol, sorbitol, GOS and fructan. The term FODMAP was coined by researchers at Australia’s Monash University.]  


What is the Low FODMAP Diet? 

A low FODMAP diet is a way of eating that temporarily reduces your intake of FODMAPs. When you eat a low FODMAP diet you choose smaller portion sizes of FODMAP-rich foods. There are just a few foods that you eliminate completely. It is usually just the first step of what is called a FODMAP Elimination Diet. The other two parts of the elimination diet process are the Reintroduction Phase and the Personalization Phase. 

What is the purpose of the Low FODMAP Diet? 

A low FODMAP diet is both a learning experience and a symptom treatment! The purpose is to find out if eating less FODMAPs can help you have fewer and less intense IBS symptoms. A low FODMAP diet can be a great way to improve your IBS symptoms and get you feeling better almost right away. Many people feel better within two weeks. A low FODMAP diet is for people with IBS and a few other digestive issues. It won’t help with other conditions. If you don’t have IBS (or IBS-like symptoms with another condition) then no benefits can be expected, and limiting yourself to a low FODMAP diet would not be worth it. 

Irritable Bowel Syndrome (IBS) 

Irritable bowel syndrome is a chronic condition that affects about 10% of Americans. It is considered a disorder of gut-brain interaction. This means that problems in communication between the gut and the brain are thought to cause most IBS symptoms. Communication between the gut and the brain is impacted by the gut microbiome, by psychological factors, other medical conditions, and by the food we eat. Nutrition is one of the most important factors impacting IBS, but it isn’t a disease that can be cured with any diet or pill. In most cases, it has to be dealt with over the years. So learning how to relieve symptoms with diet is a good investment of your time and effort. 

Irritable Bowel Syndrome

Symptoms of IBS

Abdominal pain is the major symptom of IBS, along with altered bowel habits. People with IBS may have diarrhea, constipation, or a mixed pattern of diarrhea alternating with constipation. In IBS, these symptoms occur at least one day a week, over at least three months. Many IBS patients also report bloating, which is an uncomfortable feeling of swelling and fullness from within. You can picture it like a balloon, or water balloon. Bloating might happen when there is more than the normal amount of gas or fluid in your intestines. Review your symptoms with a trusted healthcare provider and get a proper diagnosis of IBS. Some serious diseases can mimic IBS, so don’t make the mistake of diagnosing yourself in case you overlook something important.  

Symptoms of IBS

Basics of the FODMAP Elimination Diet 

Next, we’ll cover the basics of the FODMAP Elimination Diet. The diet is more than a simple list of good or bad foods, or even high or low FODMAP foods. It is actually a three-phase process. A low FODMAP diet is only the first step! Work with a registered dietitian to develop a good strategy for this process if possible. Use the Monash University Low FODMAP App, which is the very best resource available, to help you identify low FODMAP foods and portions.

Let's start with the most important basic fact you will need to know during your FODMAP Elimination Diet: depending on the portion size, a particular food might be considered high, medium or low in FODMAPs. For example, the Monash app tells us that ¼ cup of blueberries is low enough in FODMAPs to be eaten during the Elimination (Low FODMAP) Phase, while 1/3 cup of blueberries is moderate in FODMAP content, and 1 cup is considered a high FODMAP serving. 

Elimination Phase (The Low FODMAP Diet) 

The Elimination Phase works because you can learn more about how foods affect you when you reduce your intake of all FODMAPs at once than you do if you just experiment with eliminating one or a few foods at a time. For example, if you tried a “no gluten” or “no dairy” diet in the past and got only partial relief, it might be because you were still eating a lot of other FODMAPs. 

Most people follow the Elimination Phase for 2-3 weeks. During this phase, there are just a few foods that need to be completely avoided. For example, you’ll be completely avoiding onions and garlic, which are not low FODMAP no matter how small you make the serving size! Most other foods can be included during the Elimination Phase in limited servings, which are assigned a “green light” in the Monash app.  

Reintroduction Phase 

Next comes the Reintroduction Phase, which takes 6-8 weeks to accomplish. You’ll continue to this phase of the diet after a few weeks on the Elimination Phase, when you seem to have reached a good level of symptom relief. (If you didn’t get any benefit at all from the Elimination Phase, we usually recommend you stop the low FODMAP diet and go back to your usual diet.) While you continue eating a baseline low FODMAP diet, you’ll add FODMAPs back one type at a time in a controlled way while you monitor your symptoms. The purpose of the Reintroduction Phase is to find out which specific types and amounts of FODMAPs are triggering your IBS symptoms, and which ones are well tolerated. 

Personalization Phase 

Fortunately, tolerance to FODMAPs and FODMAP-containing foods is rarely all or nothing!  During the Reintroduction Phase you learn a lot about how much of each FODMAP you can handle, and the Personalization Phase is where you put it all together. For example, you might have learned that you are not a person who can eat half a plate of Brussels sprouts or loads of watermelon without a problem, but you can enjoy them in moderation! During the personalization phase, you will learn to strike the balance between variety in your diet, enjoying the foods you love, and keeping your IBS symptoms where you want them. 

High FODMAP Foods 

Sometimes it is a big surprise to learn that healthy foods can be a source of gastrointestinal distress due to FODMAPs when they are eaten in large portions! This does not make them “bad foods”. While a few high FODMAP foods or ingredients can't be considered healthy (for example, high fructose corn syrup), most are simply too much of a good thing for some people with IBS.  

A few popular foods that are contain a lot of FODMAPs are apples (fructose and sorbitol), watermelon (fructose, mannitol, fructans), cauliflower (mannitol), onions (GOS, fructans), garlic (fructans), beans (GOS, fructans), sweetened beverages (fructose), chewing gum (sorbitol) and ice cream (lactose). You can see a complete list of foods which have been lab-tested for their FODMAP content in the Monash University FODMAP Diet App.

Gluten-containing and dairy foods deserve special mention because eliminating them is a popular, but difficult, thing to do. It may be a relief to learn that gluten-containing foods and dairy foods do not have to be eliminated completely to follow a low FODMAP diet. They are not necessarily High FODMAP Foods. Gluten is not a FODMAP. It’s just a coincidence that many foods made with wheat and regular flour are high in FODMAPs, but there are exceptions, such as authentically made sourdough bread. Only the lactose (natural milk sugar) component of dairy foods is a FODMAP. Specially treated milk products which are labeled lactose-free are therefore not high FODMAP foods, nor are aged cheeses and butter, which are naturally lactose-free. 

Low FODMAP Foods 

Many foods can be considered low FODMAP in small portions only; others can be eaten in more filling serving sizes! In addition to sourdough bread and lactose-free milk products, potatoes and rice can be enjoyed instead of wheat-based foods, which are higher in FODMAPs. Greens and most salad vegetables can be enjoyed rather freely. Servings of fruits, other vegetables, nuts, seeds, and beans are kept small, to keep them low FODMAP, but they can and should be included on your low FODMAP diet to make sure you get a variety of nutrients.  

People on low FODMAP diets tend to plan meals around meat, fish, poultry, eggs, and oils because they don’t contain FODMAPs. Vegetarians or vegans who don’t eat these foods will need extra help planning their low FODMAP diets. Fortunately, tofu and tempeh have generous low-FODMAP portion sizes. 

Life After the Low FODMAP Diet 

After the Personalization Phase, you can go back to enjoying larger amounts of the FODMAPs that you proved you could successfully eat during the FODMAP Elimination Diet process. But let's keep it real; You may not be able to go back to eating large portions of foods that contain your problem FODMAPs. You’ll want to plan your meals with this in mind when you want to feel your best.  

Life After The Low FODMAP Diet

Low FODMAP Diet (PDF) 

Click here to download a PDF that explains the basics of the Low FODMAP Diet.

Do You Need Help with the Low FODMAP Diet?

If you are having trouble with the FODMAP Elimination Diet then ModifyHealth has you covered. Our fully-prepared, Low FODMAP meals make the Elimination phase of the Low FODMAP Diet quick and easy. You can have delicious, ready-to-eat Low FODMAP meals delivered to your home for free every single week. Aren't you ready to say goodbye to stomach pains and hello to feeling your best?

Click here to check out our Low FODMAP meal plans!