To better understand why FODMAPs are important, let’s take a quick look at what the digestive system does for us.

Stomach: When you eat or drink anything, it goes into your mouth, travels down your esophagus, and then into your stomach. The stomach’s purpose is to break food down through digestion and to temporarily store food. The stomach absorbs a small amount of water, minerals and vitamins. The food is then squeezed into the first part of the small intestine.

Small Intestine: The purpose of the small intestine is to further break food down, absorb nutrients, and remove waste. The small intestine absorbs about 90-95% of the nutrients, from carbohydrates, fats, minerals, protein, and vitamins from food. It also extracts water from food and removes waste from it. The small intestine has an immune function, where it acts as a barrier to bacteria. Lastly, the small intestine produces hormones that help with digestion and energy regulation. The food is them moved into the large intestine (Collins, Nguyen & Badireddy, 2024).

Large Intestine: The purpose of the large intestine is to absorb water and electrolytes from undigested food, to produce and absorb vitamins B and K through the gut microbiome, to neutralize acidity caused by fatty acids, to create antibodies that help prevent infections, and to form and move stool into the rectum (Azzouz & Sharma, 2023).

Rectum: The rectum holds stool until defecation. In other words, until it is pooped out (Azzouz & Sharma, 2023).

What is important to understand is that for people with IBD, there are places within the digestive system where there is healthy tissue as well as diseased tissue with ulcerations. When tissue becomes diseased or scarred, it can no longer perform its vital functions of nutrient and water absorption, hormone production for digestion and energy, be a bacteria barrier, neutralize acidity, or create antibodies to prevent infections. Only healthy tissue can fulfill its vital role in your digestive system. So, if the digestive system’s capabilities are reduced due to tissue damage from IBD or even food intolerances, then you need to understand which foods are difficult to digest, ones where you have intolerances, both of which can cause symptoms to get worse.

Which brings us to FODMAPs. They are a group of fermentable short-chain carbohydrates of 5 different sugar categories that are found naturally in foods, which the small intestine absorbs poorly and are difficult to digest, which can trigger digestive symptoms in some people with gut issues, like IBD. When these sugar categories are not absorbed in the small intestine, they tend to travel to the large intestine, untouched and pulling water with them as they go creating a feeling of fullness, pain, diarrhea, and sometimes even constipation. When FODMAPs reach the large intestine, they serve as food for the gut bacteria causing gas and distension of the abdomen (Johns Hopkins Medicine, 2024; Smith & Jaffee, 2018).

A low-FODMAP diet has been shown to decrease symptoms by up to 75% for bloating, pain, diarrhea, constipation, mood changes, and fatigue. If you are going to follow this diet, it is important to work with a registered dietician with experience in IBD. Do not attempt this on your own, as the biggest risk for you would be malnutrition and that is something we want to avoid. The low-FODMAP diet is only intended to be used when you are having flares, not for when you are in remission from IBD (Cleveland Clinic, 2022; Canadian Digestive Health, 2024; Johns Hopkins Medicine, 2024; Smith & Jaffe, 2018).

So, let’s dive a little deeper into what FODMAPs are. “FODMAP” is an acronym. Let’s start with the “F”:

F: Fermentable – The F in FODMAP stands for carbohydrates in the sugar category of “fermentable.” 

Definition: Fermentable carbohydrates represent all foods that your gut bacteria feed upon, converting them to gases in a chemical process called fermentation. Fermentable carbohydrates are sugars that bacteria in your large intestine break down, which causes the release of gas and other by-products (Cleveland Clinic, 2022; Canadian Digestive Health, 2024; Johns Hopkins Medicine, 2024).

So, if you have Crohn’s disease, there is likelihood of tissue damage in the small intestine. Any nutrients from food that does not get properly absorbed by enough healthy tissue in the small intestine, will move on to the large intestine where it will begin to ferment and create, for example, gas.

For the 2 years before I was diagnosed with Crohn’s disease, when I’d eat, my stomach would swell up like a basketball. It would be painful to even touch it. This was my very first symptom of IBD. I knew something was wrong, but none of the doctors could identify the issue, even after a ton of testing. Now, I understand that the significant tissue damage in my small intestine meant far less of what I ate was getting absorbed. Instead, it simply passed through to the large intestine where it fermented until my stomach swelled so much, I looked like I was 8-months pregnant. Not to mention the impact of inflammation from a disease I was completely unaware of at the time.

Examples include: beans, onion, garlic, apple, cabbage, dairy, wheat, oranges (citrus)

We must remove the peeling of any fruit or vegetables we eat from the safer foods list. This is because when it comes to IBD, we can no longer digest that outer peeling. Now, let’s talk about apples. They are high in insoluble fiber, which is fiber that has a strong structure and does not disintegrate when put into a glass of water. Apples are difficult to digest, and can trigger IBD symptoms (Steinhart & Cepo, 2008/2022, p. 92; Shepherd, 2013/2014, p. 8; Crohn’s and Colitis Foundation, 2023). Even apple juice from putting an apple through a juicer that removes most of the fiber is something that would likely not be tolerated by someone with digestive issues because of the high level of fructose.

Let’s talk about wheat. There is a food item called “Seitan” [SAY-tan], which is a wheat, gluten protein source that resembles the texture of meat in many vegan processed foods. Wheat is a high inflammatory food, high in FODMAPs, and can worsen IBD symptoms. It contains gluten that increases inflammation. Wheat is one of the “Big 8” allergens noted by the United States Food and Drug Administration (FDA) (Shepherd, 2013/2014, p. 8). In 2021, another item was added to the list that is now referred to as the “Big 9.”

So, if wheat is out, what is a substitution? One alternative to wheat (and there are many) is cassava (or sometimes it is called yucca root). It is gluten-free, reduces inflammation, is low in FODMAPs, is a prebiotic (which is what feeds the probiotics), autism approved, and most interestingly is a hypoallergenic food (Gundry, 2018, p. 20).

SIDE NOTE: There are ways to prepare beans (the legumes) so that they can be digested properly without causing as much inflammation. This matters because beans are an excellent source of protein, which we need in our diet. There are parts of the onion and garlic plants that you can eat cooked that should not cause you problems. All apples, cabbage, dairy, and wheat are out. Oranges can be prepared in such a way as to cause less of an issue. Lastly, there are precise single portion limits to FODMAPs that you can likely tolerate on a low-FODMAP diet. The single portion limits cannot be overlooked. It is an important part of successfully navigating the low-FODMAP diet.

O: Oligosaccharides – The O in FODMAP stands for carbohydrates in the sugar category of “oligosaccharides.” 

Definition: Highly fermentable, soluble plant fibers know as prebiotics, which feed the beneficial bacteria in your gut (Cleveland Clinic, 2022; Canadian Digestive Health, 2024; Johns Hopkins Medicine, 2024).

Examples include:

Under the Galacto-oligosaccharaids subcategory, examples include legumes and pecans. As mentioned before, there are ways to prepare the appropriate legumes so that they can be digested properly without causing as much inflammation. And unfortunately, pecans are out.

Under the Fructans subcategory, examples include garlic, onion, and wheat. There are parts of the garlic and onion plants that you can eat cooked that should not cause you problems. And, wheat is out. I do have alternatives for wheat, so be on the lookout for that.

D: Disaccharides - The D in FODMAP stands for the carbohydrates in the sugar category of “disaccharides.”

Definition: Lactose is the fermentable sugar in this group; the sugar found in dairy and human milk (Cleveland Clinic, 2022; Canadian Digestive Health, 2024; Johns Hopkins Medicine, 2024).

Examples include:

Under the Lactose, which includes glucose & galactose subcategories, an example is dairy, which is completely out.

Under the Sucrose subcategory, an example is apple, which is completely out.

But don’t worry, I do have alternatives for both dairy and apples, so be looking for those.

M: Monosaccharides – The M in FODMAP stands for the carbohydrates in the sugar category of “monosaccharides.”

Definition: Fructose, the sugar in fruit, is the fermentable sugar in this group … not all fruits are affected (Cleveland Clinic, 2022; Canadian Digestive Health, 2024; Johns Hopkins Medicine, 2024).

Examples include:

Under the subcategory where the ratio of fructose is greater than glucose, examples include grapes, pears, pineapples, cherries, and oranges.

Under the subcategory of Galactose, we have oranges.

Remember, from earlier in this segment, oranges can be prepared in such a way as to cause less of an issue within the right single portion size limit is used.

A: and – The A in FODMAP stands for “and,” merely so the acronym would make something easier to say and therefore remember. It’s very clever.

P: Polyols – The P in FODMAP stands for the carbohydrates in the sugar category of “polyols.”

Definition: These are sugar alcohols that humans can only partially digest and absorb in the small intestine. They are commonly used as artificial sweeteners and are also found naturally in some fruits (Cleveland Clinic, 2022; Canadian Digestive Health, 2024; Johns Hopkins Medicine, 2024).

Note: You might be asking yourself, if I have ulcerative colitis and not Crohn’s disease, then why would I bother with learning about polyols at all? Here is what you need to know. ALL humans have a difficult time digesting polyols in their small intestine, not just people with IBD. And today we have learned that if something doesn’t get properly absorbed in the small intestine, what’s left moves on to the large intestine to sit there and ferment.

Examples include:

Under the subcategory of sugar-free diet products, examples include artificial sweeteners and diet soda, where both are out.

Under the subcategory of natural sources, examples include peaches, cauliflower, and bell pepper, which are all out.

The low-FODMAP diet was introduced in 1999 by a nutritionist, Dr. Sue Shepherd, as the first scientifically proven diet that provided any kind of symptom relief for patients with diagnosed digestive problems like celiac disease, irritable bowel syndrome (IBS), and inflammatory bowel disease (IBD). She received her PhD from Monash University. Since then, FODMAPs have been extensively studied by the Department of Gastroenterology at Monash University in Melbourne Australia, providing guidance on each applicable food item within the 5 sugar categories (Shepherd, 2013/2014, pp. 1, 3, 238).  Periodically, updates are made, so be sure to stay up to date with new findings from the Monash research on FODMAPs.

The Three-Step Protocol According to Monash University:

Elimination Phase: Adhere to a diet focused on low-FODMAP foods while restricting high FODMAP foods for a limited time. Ideally this should be done with a nutritionist or dietician to ensure that all of your nutritional needs are being properly met.

Note. On average, this phase lasts approximately four weeks. However, flares can last from days to months. This should be considered, based on your specific flare at the time.

Reintroduction Phase: Gradually reintroduce higher fodmap foods back into your diet. This process takes time. Go slowly so that you can properly gauge which foods are tolerated and at what amount. This stage is crucial because it will allow you to eventually eat a much more varied diet over time.

Personalization Phase or “Liberation”: At the end of this diet you will have a better understanding of what foods you can comfortably tolerate and which are best avoided.

Consider only adding a new food item in the reintroduction phase when both conditions have been met:

One: At least 48-hours (2 full days) have passed since the reintroduction of a new food item; and

Two: There have been no observable reactions to any food items in the last 48-hours (2 full days).