A Low FODMAP Diet Helps IBS & Gluten Sensitivity.

By Amy Burkhart MD, RD

Updated 2024

A  new study found a low-fodmap diet more helpful than medication in decreasing the symptoms of irritable bowel syndrome (IBS).

Just four weeks on a low-FODMAP diet improved common symptoms of IBS, such as diarrhea and constipation, in 76% of people who followed the diet. Those taking medications to treat IBS symptoms only saw improvement 58% of the time. Surprisingly, a third group who followed a traditional low-carbohydrate diet also improved more than the group taking medication. This is a shift in thinking about how IBS is treated since, traditionally, medications were one of the main treatments used for people with IBS. For those not familiar with the low-FODMAP diet, let’s look deeper into this diet plan that can be life-changing for IBS sufferers.

FODMAP stands for fermentable oligo-, di-, monosaccharides, and polyols. These are carbohydrates that commonly cause digestive problems such as diarrhea, constipation, bloating, and gas. FODMAP intolerance is connected with up to 75% of cases of irritable bowel syndrome.

FODMAP carbohydrates exist in wheat and foods like apples, watermelon, onions, and garlic. These carbohydrates tend to be poorly absorbed, leading to issues such as gas, bloating, diarrhea, depression, joint pain, and fatigue in susceptible individuals.

There are four types of FODMAP sugars:

• Oligosaccharides: Wheat, rye, legumes, and various fruits and vegetables, such as garlic and onions.
• Disaccharides: Milk, yogurt, and soft cheese. Lactose is the primary carb.
• Monosaccharides: Sweeteners such as honey and, agave nectar, and fructose (fruit sugar)
• Polyols: Certain fruits and vegetables, including blackberries and lychee, as well as some low-calorie sweeteners like those in sugar-free gum

Some foods contain just one type of fodmap sugar, while others contain several  Common problematic FODMAP-containing foods, including wheat, apples, onions, garlic, honey, legumes, and milk. But, the list of FODMAP-containing foods is much more extensive.

There is no laboratory test for FODMAP intolerance. The diagnosis is made after evaluation for other causes of symptoms, followed by a FODMAP elimination diet. The diet must be done correctly to assess whether or not FODMAP intolerance is present.

The diet is complicated, and I recommend consulting a registered dietitian to discuss its proper implementation. If the diet is not done correctly, FODMAP intolerance may be missed as a diagnosis.

The treatment for FODMAP Intolerance is a low-FODMAP diet. A two- to three-week trial period is recommended. Typically, some improvement will be seen in that period. If the diet has been done correctly and no progress has been made, it is unlikely the person has FODMAP intolerance. If there is an improvement, the low FODMAP diet should be continued for six weeks. A methodical reintroduction diet is recommended after six weeks on a low FODMAP diet.

The diet is not meant to be a long-term solution to digestive problems. Long-term adherence to a low FODMAP diet causes negative changes in the gut microbiome.

No. The low fodmap diet is not a gluten-free diet.

It is low in gluten, but it is not strictly gluten-free. For example, some people on a low FODMAP diet can tolerate sourdough spelt bread. The fermentation process breaks down the FODMAP sugar in spelt. Spelt bread contains gluten and would not be allowed on a gluten-free diet. This is one example of gluten being allowed on the Low FODMAP diet. There are others beyond the scope of this article.

Researchers investigating gluten sensitivity were surprised to discover that the majority of individuals experiencing symptoms after consuming wheat were not reacting to gluten. Instead, the culprit in most cases was FODMAP sugars, commonly found in wheat and various other foods.

Remarkably, when these subjects eliminated FODMAP-containing foods from their diet, they experienced significant improvement. Only 8% of those with “Non-Celiac Gluten Sensitivity” had no reaction to gluten after reintroducing only gluten without the presence of other FODMAP foods. It wasn’t the gluten causing their symptoms; it was the foods containing FODMAPs.

The implications of this study are profound. If individuals with gluten sensitivity are primarily reacting to FODMAP carbohydrates, the recommended treatment is not a gluten-free diet but rather a low-FODMAP diet. A gluten-free diet and a low-FODMAP diet are vastly different.

The link between these carbohydrates and symptoms is now well accepted, and the Low FODMAP diet relieves many symptoms. Also, the Low FODMAP diet is now the primary dietary intervention for IBS. Since there is currently no test for FODMAP intolerance, proper diet implementation is imperative to determining the presence or absence of FODMAP intolerance. I again emphasize the importance of consulting a dietitian familiar with the diet. Doing it without guidance is difficult.

Following is a list of valuable resources for anyone interested in learning about a Low FODMAP diet. Low FODMAP product lines and food delivery services are now available.

1. Monash University Low Fodmap App for iPhone and Android
2. Monash University Website: The leaders in research and information on the low FODMAP diet
3. Patsy Catsos, RD–  Reputable website with information on following a low FODMAP diet
4. Pinterest site with photos of low FODMAP products
5.  Kate Scarlata, RD: A  reputable blog with recipes and information on a low FODMAP diet written by a registered dietitian
6. Book: A great consumer-friendly resource for anyone on a Low FODMAP Diet. Written by Dr. Sue Shepard and Peter Gibson from Monash University

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• Low FODMAP diet and Inflammatory Bowel Patients with IBS; effect on microbiome