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The Low FODMAP Diet 101

So, you’ve been diagnosed with Irritable Bowel Syndrome…

And your doctor hands you a sheet of paper titled, “The Low FODMAP Diet” containing what looks like an intimidatingly long list of foods to avoid, including some of your favorites like ice cream, pasta, and cauliflower. Your heart starts beating faster, your stomach starts churning and that feeling of being completely overwhelmed sets in. Now what?

You are not alone if feeling flustered when it comes to managing IBS. In this section, I’ll break down what a FODMAP is, which foods to eat, which foods to avoid, and other ways to help you thrive you as you begin this journey towards feeling your best and enjoying your food along the way. Keep in mind, the Low FODMAP Diet is by no means a cure, but is regarded as the best tool to relieve and manage the most common symptoms.


FODMAP is an acronym for Fermentable Oligosaccharides, Disaccharides, Monosaccharides and Polyols. These are short chain carbohydrates that are fermentable and poorly absorbed by the small intestine. (2)

Oligosaccharides are the longest chain carbohydrates. They are typically found in wheat and rye products, legumes, cashews, artichokes, onion and garlic. (2)

Disaccharides are usually refers to lactose, a sugar found in milk and other dairy products. Lactose is typically found in cow’s milk, evaporated milk, buttermilk, custard, cream, yogurt and ice cream. (2)

Monosaccharides usually refers to fructose. It is the shortest chain carbohydrate and is found in fruits suchas apples, pears, watermelon and mango, natural sweeteners such as honey, and artificial sweeteners like high fructose corn syrup. (2)

Polyols, or sugar alcohols, typically refer to mannitol and sorbitol. These are present in stone fruits (apricots, cherries, plums), cauliflower, mushrooms, and snow peas. Artificial sweeteners like xylitol and isomalt are also considered part of this group. (2)


In the case of Oligosaccharides, there is no human enzyme that can break them down and therefore are not easily absorbed by the small intestine. They are also highly fermentable, meaning that gut bacteria feed on them and create gas as a byproduct. This build-up of gas can lead to bloating, excessive flatulence, and abdominal pain.

Disaccharides, Monosaccharides and Polyols, on the other hand, tend to absorb slowly and therefore linger inside the intestine longer. As the concentration of these short chain carbohydrates increases in the intestine, water flows into the lumen by osmosis in an attempt to reach equilibrium. This increase in intestinal fluid can lead to bloating and diarrhea.


The Low FODMAP diet is not a cure, but if adhered to, studies show it can improve IBS symptoms in 75% of cases1. However, it is restrictive and can be difficult to adhere to which is why it is often advisable to work with a nutritionist.


This is the most restrictive part of the process. The current recommendation is to follow a strict low FODMAP diet for 4-6 weeks. Continuing the diet beyond this time period could lead to vitamin deficiencies in Folate, Thiamin, B6, Calcium and Vitamin D as well as could disrupt the microbiome creating further dysbiosis.


The second phase of the diet is often referred to the as the “reintroduction phase” in which you begin to incorporate high FODMAP foods back into your diet. Many find this process tedious because foods can only be brought back one at a time and in limited amounts. It’s suggested to only try one type of food per day on its own and document any symptoms that may result (pain, severe bloating, diarrhea, constipation, headaches, skin rashes, eczema, etc.) Keeping a food diary can be an excellent way to keep track of when a food was eaten, how much, and if any symptoms occurred. Sometimes the effects of food can take a couple of days to manifest and therefore it’s recommended to wait 2-3 days before trying a new food.


The final phase is slowly incorporating as many high or medium FODMAP foods back into one’s diet avoiding only those foods that trigger symptoms. This process can take months to years but is crucial to building up the beneficial bacteria in your gut and ensuring that the body’s nutritional needs are being met.


A nutritionist has experience and knowledge of FODMAPS and can offer recommendations for ordering at a restaurant, recipes, and nutrition education to set you up for success. Furthermore, they can assist in planning, implementation, and monitoring of the diet to ensure that it works for your lifestyle and food preferences. This diet, if not implemented properly, can lead to nutrient deficiencies, and therefore it’s important to work with someone who can verify that your body’s nutrition requirements are being met. The road to managing IBS is often not a straight one. It can have many twists, turns, and unfortunate set-backs. Having a dietary professional guiding and offering support can help to stave off frustration and keep you on track to feeling your best.


1. Altobelli E, Del Negro V, Angeletti PM, Latella G. Low-FODMAP Diet Improves Irritable Bowel Syndrome Symptoms: A Meta-Analysis. Nutrients. 2017;9(9):940. Published 2017 Aug 26. doi:10.3390/nu9090940

2. Barrett JS. How to institute the low-FODMAP diet. J Gastroenterol Hepatol. 2017 Mar;32 Suppl 1:8-10. doi: 10.1111/jgh.13686. PMID: 28244669.

3. Dwyer E. The 3 steps of the FODMAP diet. The 3 phases of the low FODMAP diet- A blog by Monash FODMAP | The experts in diet for IBS - Monash Fodmap. Published January 15, 2018. Accessed February 2, 2021.

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