Low FODMAP diet
Kate Watson
Kate WatsonRegistered Dietitian

What are FODMAPs and a Low FODMAP diet?

Published on January 11, 2021


If you are like most people researching a Low FODMAP diet, chances are your doctor handed you a sheet of paper about the diet or told you to look it up online. That was my experience many years ago as a patient. Even though I was a dietitian, I was left feeling confused and overwhelmed. To begin with, what the heck does that weird sounding name even mean?

“FOD.. wha???” I’ve heard many interesting pronunciations of this word over the years, but it’s pronounced just like it’s spelled: “FOD-MAP” (not FOODMAP). The Low FODMAP diet is the only scientifically researched diet for the treatment of IBS, improving symptoms for 60-80% of people who follow it correctly*. As a dietitian, I’ve personally seen it change lives of many patients over the years, myself included!

What does FODMAP stand for?

The word FODMAP is an acronym for a group of short chain carbohydrates (certain sugars and fibers) which may be poorly absorbed or not absorbed at all in the small intestine. FODMAP stands for Fermentable Oligosaccharides, Disaccharides, Monosaccharides, and Polyols.

F = Fermentable refers to the process where bacteria in our intestines eat FODMAPs, producing gas and stretching the intestines. Fermentation is a normal part of digestion, but it can cause discomfort, excess gas, and bloating in those with IBS. FODMAPs also pull water into the intestines which may cause diarrhea and bloating.

O = Oligosaccharides refer to galactans (GOS) and fructans which are found in foods like beans, nuts, wheat, garlic, and onions. Humans lack the enzyme to break down oligosaccharides, so they are malabsorbed in all people; however, people with IBS are especially susceptible to symptoms.

D = Disaccharides refer to lactose, the sugar found in milk, yogurt, fresh cheeses and ice cream. Most people have an enzyme called lactase that aids absorption of lactose; for people without lactase, lactose is not digested and can cause symptoms like gas, bloating, and diarrhea.

M = Monosaccharides refer to fructose (or fruit sugar) in excess of glucose. The body needs equal levels of fructose and glucose for proper absorption. Foods with higher levels of fructose than glucose include honey, mangoes, agave, apples and pears.

A = And

P = Polyols are sugar alcohols found naturally in certain fruits and vegetables like mushrooms, cauliflower, apples, and pears. Polyols like mannitol and sorbitol are often used as additives in sugar-free foods, chewing gums, and candies.

While it’s not necessary to learn what each of these words mean, the types of FODMAPs will become important later when you investigate which, if any, may be triggering your GI symptoms.

Three Phases of the Low FODMAP diet

  1. Elimination Phase
  2. Reintroduction Phase (also known as the Challenge phase)
  3. Modified Phase (also known as the Integration or Personalization phase)

1. Elimination Phase

During the Elimination Phase, all high FODMAP foods are removed for a period of 2-6 weeks. The goal is to understand if removing FODMAPs from your diet actually improves your symptoms. If it does, you will go onto the second phase, the Reintroduction Phase. If not, it’s likely that FODMAPs were not causing your symptoms in the first place (or that you accidentally consumed FODMAPs during the Elimination phase). Read more details about the Low FODMAP Elimination Phase.

I have found that many patients get stuck in the FODMAP Elimination Phase because they feel so much better and don’t want to trigger symptoms by re-introducing foods. Resist this urge! The Elimination Phase is extremely restrictive, and it’s important for your overall health and the health of your gut microbiome to re-introduce as many foods as possible.

To ensure your nutritional needs are met during the Elimination Phase, it’s always a good idea to navigate the Low FODMAP diet with the help of a FODMAP-trained dietitian.

2. Reintroduction Phase

The goal of the Reintroduction Phase is to determine which FODMAPs are triggers for you personally and in what quantities. In this phase, you will try consuming foods that contain one of the six common FODMAPs groups, one at a time:

  • Galactans (GOS)
  • Fructans
  • Lactose
  • Fructose
  • Mannitol
  • Sorbitol

During Reintroduction, many people find they can safely tolerate small amounts of high FODMAP foods and are pleasantly surprised that some FODMAP groups may have little or no impact on their symptoms. Read more details about the Low FODMAP Reintroduction Phase.

3. Modified Phase

In this phase, you will modify the Low FODMAP diet based on what you learned in the Reintroduction Phase. You will add back the FODMAP foods you passed in the challenges and continue to restrict the ones that triggered your symptoms. The goal of this phase is to find the most varied, nutritious diet possible while minimizing your IBS symptoms. The more foods you are able to eat, the easier it will be to adhere to the diet long-term.

Navigating the diet

Though getting started on a low FODMAP diet may seem daunting, it’s easier than ever thanks to new resources available. Monash University tests foods for FODMAP content and features their results in the FODMAP app. The Fig phone app lets you scan products at the grocery store and see if they are likely Low FODMAP or not. You can also search for hard-to-find products at more than 100 grocery stores.

The Low FODMAP diet won’t work for everyone who tries it, but it’s certainly worth a try if you’ve been suffering with IBS symptoms. The effort you put forth will pay off when you finally learn what your personal triggers are and hopefully find symptom relief.

Continue reading: Getting started with the Low FODMAP Elimination Diet

Check if grocery products are low FODMAP here.