Low Fermentable Oligo-, Di-, Mono- Sacharrides and Polyols (FODMAP) Diet
The majority of people who suffer from irritable bowel syndrome (IBS) associate the onset of their gastrointestinal symptoms with the intake of a particular food. Although reasons for food intolerance are not entirely known, the most common foods that trigger IBS symptoms, such as spicy and processed foods, certain vegetables, coffee and alcohol, are all avoided in the “traditional” IBS diet. Researchers at Monash University were the first to propose a physiological mechanism for the observed food sensitivity in gastrointestinal disorders. They found the link between IBS symptoms and particular carbohydrates present in a variety of foods - fermentable oligo-, di-, mono-sacharrides and polyols (FODMAP). FODMAP are poorly absorbed in the small intestine, but are rapidly fermented by the bacteria in the colon. Bacterial fermentation is thought to be responsible for a variety of processes that cause IBS symptoms, such as gas, bloating and altered bowel habits.
Foods are categorized as low or high FODMAP items based on the amount of short-chain carbohydrates present in them (see the graphic for some examples). Low FODMAP diet does not mean that all foods with high FODMAP load need to be eliminated. The diet aims to reduce the consumption of high FODMAP food while emphasizing low FODMAP alternatives. Implementation of this diet is best done in consultation with a nutritionist, as drastic
elimination of certain foods can lead to nutritional deficiencies.
Not all IBS sufferers are sensitive to FODMAP. To test whether the FODMAP are causing some of your symptoms, avoid all high FODMAP foods for 4 weeks. In most cases, people who are sensitive to FODMAP will notice significant symptom relief within first few weeks.
As can be seen from the table, many items that are high in FODMAP are rich in nutrients and you do not want to remove them from your diet unless it is necessary. For this reason, the 4-week elimination phase should be followed by the gradual re-introduction of high FODMAP foods into your diet. This "challenge phase" should unfold slowly: introduce foods one by one,
with waiting periods of 2-3 days, to allow for possible symptoms to develop. If no symptoms appear, keep re-introducing different foods until the culprit is found. Keeping high FODMAP foods that are not responsible for IBS symptoms in your diet is very important, as it helps minimize possible nutritional deficiencies.
Long term effects of low FODMAP diet are still unknown. Certain high FODMAP foods, like onion, garlic, and asparagus, also contain prebiotics - substances that help grow and maintain the good bacteria in the gut. Given the importance of the gut microbiome in IBS, it is not clear what kind of consequences restrictions in FODMAP might have for the diversity of the gut bacteria. This potential shortcoming can possibly be solved by taking supplements with the right strains of bacteria. Additionally, low FODMAP diet can result in reduced fiber intake. This issue can also be addressed with adequate supplementation.
For a more detailed look at low FODMAP diet and how to apply it, consult these excellent books written by experts in the field:
The Complete Low-FODMAP Diet: A Revolutionary Plan for Managing IBS and Other Digestive Disorders
The Low-FODMAP Diet Cookbook: 150 Simple, Flavorful, Gut-Friendly Recipes to Ease the Symptoms of IBS, Celiac Disease, Crohn's Disease, Ulcerative Colitis, and Other Digestive Disorders
Last updated: December 18, 2016