A variety of fresh meats, fruits and vegetables surrounding a chalkboard that spells fodmaps

What Are Fodmaps?

If you are at all interested in gut health, you have probably heard of the low fodmap diet. You may be wondering, what actually are fodmaps? No, that’s not foodmap – it’s F.O.D.M.A.P. and it stands for Fermentable Oligosaccharides, Disaccharides, Monosaccharides, And Polyols.

If those words mean nothing to you, hang with me for a minute! Let’s break it down. The word “saccharide” means sugar. The pre-fixes “oligo”, “di” and “mono” refer to the number of sugar molecules strung together as listed below.

  • Oligo = typically 3-10
  • Di = 2
  • Mono = 1

Now, these terms are actually categories of sugars based on their chain length, so not every sugar within each category is a fodmap. For example, glucose belongs to the monosaccharide group, but it is not a fodmap and I will explain the difference later on. The specific fodmap sugars are as follows:

  • Fructans and galactooligosaccharides (GOS) = Oligosaccharides
  • Lactose = Disaccharide
  • Fructose = Monosaccharide
Chemical structure of lactose, two sugar molecules attached to each each other.

What about polyols you say? They may seem like the odd man out but not completely. Polyols are sugar alcohols and they also belong to the fodmap category.

What Foods Contain Fodmaps?

So, fodmaps are sugars, chains of sugars, and sugar alcohols that are fermentable. They are found in certain varieties of fruits, vegetables, grains, dairy, beans and legumes. Some examples include watermelon, blackberries, avocado, garlic, wheat, cow’s milk and black beans.

Fodmaps are also found in some man made substances like sugar free products that contain sugar alcohols like sorbitol or xylitol. Sweeteners such as high fructose corn syrup or honey are also high fodmap.

How Do Fodmaps Differ From Other Sugars?

Since not every di, mono and oligosaccaride is high fodmap, what differentiates them? This is where the F – fermentable, comes in. Fodmaps are sugars that are not only fermentable, but RAPIDLY fermentable. This sets them apart from other sugars that are non-fermentable or slower to ferment in our bodies. This rapid fermentation is also why they can cause problems.

Our natural gut bacteria actually help us digest certain, non-digestible, or less digestible substances in our diet including fodmaps. This process is “fermentation” and it’s not just for wine or kimchi.

This actually occurs in our body too, and is meant to be a helpful to us. These bacteria digest substances that we don’t and the rest leaves our body as stool.

The Low Fodmap Diet

So now that you know what fodmaps are, you may be wondering why would someone want or need to follow the low fodmap diet? It is most commonly used for people who have certain gastrointestinal conditions like irritable bowel syndrome (IBS), small intestinal bacterial overgrowth (SIBO) and inflammatory bowel diseases (IBD) among others.

The byproduct of bacterial fermentation in our body is gas production, sometimes a lot of it. When this happens rapidly in our GI tract, it can cause discomfort, bloating and of course cause us to pass excessive gas. Fodmaps can also draw extra water into the intestinal tract which can cause diarrhea as well.

Often, people with IBS may experience visceral hypersensitivity – increased sensation of pain in their gut. For them, rapid fermentation may cause pain or an increased sense of bloating. On another spectrum, someone with SIBO has a displacement of their gut bacteria into the small intestine (most of our bacteria should be in the large intestine) as well as an imbalance in numbers of these bacteria.

Fermentation in the small intestine can be uncomfortable because our smaller diameter of the small intestine cannot accommodate for gas production like the large intestine can. These are just several examples of when a low fodmap diet may be helpful.

Virtual dietitian meeting with a client. She is looking at her laptop, smiling and waving.

While the low fodmap diet can be beneficial, it’s not quite as simple as it may sound. The diet itself is extensive and has several different phases to it. For more detailed information on the phases of the low fodmap diet see my post “Phases of the Low Fodmap Diet: Elimination, Challenge and Re-Introduction”.

Further, due to its restrictiveness, it is not necessarily meant to be followed long term. It is important to work with a GI dietitian who is familiar with the low fodmap diet to guide you and help you determine if it may be right for you.


In summary, fodmaps are different types of sugars that our natural gut bacteria rapidly ferment. While a helpful process to many, this can cause unpleasant symptoms in some individuals. These people may need to limit their fodmap consumption via the low fodmap diet.

As always, thanks for reading!