Should I Go On the Low FODMAP Diet?

by Amylee Amos MS, RDN, IFMCPNutrition
Assorted foods with chalkboard reading 'fodmap'

What is the Low FODMAP diet?

The Low FODMAP diet is a temporary elimination diet that is useful for individuals with certain gastrointestinal issues such as Irritable Bowel Syndrome (IBS). It was originally developed in 2005 at Monash University in Australia. 

FODMAP stands for fermentable oligo-, di-, mono- saccharides and polyols. Breaking it down further, when the microbes in our gut come into contact with fermentable sugars including FODMAPs, they ferment gas. Oligosaccharides include fructans such as wheat, rye, beans, garlic, and certain vegetables. Disaccharides include the sugars found in dairy products. Monosaccharides include fructose such as that found in fruits, honey and high-fructose corn syrup. Finally, polyols are sugar alcohols such as xylitol and sorbitol.

These classes of sugars are poorly absorbed in the gut in certain people. In such individuals, the sugars ferment in the gut causing abdominal distention, gas, bloating, and other gastrointestinal manifestations. In the low FODMAP diet, all of these foods and food groups are greatly reduced. 

Many people confuse the reason why these food groups are eliminated. For example, individuals often eliminate wheat from their diet for conditions such as autoimmune diseases. However, normally, wheat is removed from the diet as a means to avoid gluten, a protein found in wheat. In the low FODMAP diet, the proteins such as gluten are not an issue, rather the sugars or carbohydrates (specifically the oligosaccharides in the case of wheat) in the high FODMAP foods are the target for elimination (1,2). 

Who is the Low FODMAP diet for?

The low FODMAP diet has been most studied as a treatment for IBS. IBS presents differently in different people, most people’s symptoms are either diarrhea-dominant or constipation-dominant. The low FODMAP diet may work for both types of IBS, but appears to have the strongest effect on those with diarrhea-dominant IBS. Even for individuals who have never been diagnosed with IBS, but have persistent and idiopathic gas, bloating, and abdominal pain, the low FODMAP diet may be indicated. 

The low FODMAP diet is also recommended for certain individuals with small intestinal bacterial overgrowth (SIBO) because SIBO is characterized by abnormal fermentation of carbohydrates. However, it has not been well studied in this population of patients and the majority of research is currently anecdotal. 

Does the Low FODMAP diet work?

Critics of the low FODMAP diet have argued that studies showing its effectiveness are of low methodological quality. However, all nutrition intervention studies are challenging to carry out. The best results of the low FODMAP diet are seen in those with IBS. Studies show that IBS patients who utilize the low FODMAP diet as a therapeutic intervention show improvements in stomach pain, gas, bloating, and diarrhea (3-5).

How to implement the low FODMAP diet

The low FODMAP diet is dose-dependent, meaning that the more high FODMAP foods you can eliminate, the greater the effect of the diet. Understanding which foods should be eliminated is critical to the success of the diet. That being said, certain high FODMAP foods that are removed in the low FODMAP diet are extremely healthful foods, and specifically many of the vegetables eliminated are especially beneficial for gut health. Oligosaccharides such as artichokes, asparagus, onions, and garlic, which need to be removed in the low FODMAP diet, are rich in prebiotic fiber that keep the healthy bacteria in the gut microbiome healthy and flourishing. Thus, it is critical to remember that the low FODMAP diet is a temporary elimination and re-challenge diet that should only be implemented under the guidance of a registered dietitian. 

The low FODMAP diet begins with an induction phase, where the individual following the diet eliminates all high FODMAP foods for 4-6 weeks. A full list of high and low FODMAP foods and other resources for following the low FODMAP diet can be found at Monash University. If symptoms have improved after 6 weeks, the individual undergoes a challenge phase. Alternatively, if after 6 weeks there has been no symptom improvement (despite strictly following the diet), FODMAPs are likely not the source of gastrointestinal distress and thus the diet should be discontinued. Assuming that symptoms have improved, the challenge phase is designed to identify high FODMAP foods that are not the source of gastrointestinal distress with the intention to liberalize the diet as much as possible. In the challenge phase, the various groups of FODMAPs are introduced one by one to identify all of the foods that can still be included in the diet without causing symptoms (1,2). The challenge phase is often something that needs to be repeated over time with foods that have continued to be eliminated because in many cases the diet can be further liberalized as gut healing occurs. 

What are the risks of the Low FODMAP diet?

The Low FODMAP diet is a very safe way of treating gastrointestinal distress including flatulence, bloating, abdominal pain and distension, and other GI symptoms. However, if low FODMAP foods are restricted for a prolonged period of time, there may be adverse effects such as alterations to the gut microbiome and micronutrient deficiencies. This is why it is imperative to follow the low FODMAP diet under the guidance of a registered dietitian or other healthcare practitioner who is trained in the low FODMAP diet. The goal is to eliminate as few foods as possible for as short a period of time as possible. 

Should I go on the Low FODMAP diet?

If you have been diagnosed with IBS or have chronic gastrointestinal symptoms such as diarrhea, gas, and bloating, it is worth trying the low FODMAP diet to see if FODMAP fermentation is causing your symptoms. At the Amos Institute, we specialize in cognitive decline and Alzheimer’s disease. The gut and the brain are intricately connected, making addressing gut health essential when we work to optimize brain health. Because of the bidirectional link between the gut and brain, our registered dietitians are trained in how to safely and effectively implement the low FODMAP diet and other therapeutic diets for gut health. Contact the Amos Institute today to request an appointment to help you implement the low FODMAP diet. 


References: 

  1. Guilliams, T.G. (2016). ISBN: 978-0-9856158-3-3
  2. Rakel, D. (2018).  Integrative medicine (4th ed.).
  3. Shepard, et al. 2014. https://doi.org/10.1097/MCO.0000000000000116. 
  4. Khan et al. 2015 https://doi.org/10.1007/s10620-014-3436-4
  5. Marsh et al (2016). https://doi.org/10.1007/s00394-015-0922-1