How The Low-FODMAP Diet Can Help Manage Irritable Bowel Syndrome

Laura Manning, MPH, RD, CDN

Clinical Nutrition Coordinator

Susan and Leonard Feinstein IBD Clinical Center at Mount Sinai

Abdominal pain and a swollen belly, gas, constipation, or diarrhea—these symptoms of irritable bowel syndrome (IBS) affect one in seven American adults. A common gastrointestinal (GI) disorder, IBS is a long-term but not life-threatening condition. Still, it can interfere with many aspects of daily life, and is one of the top reasons for missing work.

There is no specific test for IBS, so gastroenterologists typically diagnose it only after testing for and ruling out all other GI problems. We do not know exactly what causes it, and so far there is no cure, so treatment focuses on controlling symptoms.

Traditionally, IBS has been managed in many different ways, including dietary intervention, supplements, and medications like anti-cramping and anti-diarrheal drugs. A relatively recent approach, called the low-FODMAP diet, has helped many people with IBS and is fast becoming the new gold standard for managing symptoms.

What Does ‘FODMAP’ Mean?

FODMAP is an acronym for a group of carbohydrates: fermentable oligosaccharides, disaccharides, monosaccharides, and polyols. These are sugars that occur naturally in a variety of foods and are added to many processed foods. They are normally good for us, but people with IBS tend to be sensitive to them. FODMAP foods include:

Fructose. Typically found in many fruits, like watermelon, apples, and cherries, as well as honey and high-fructose corn syrup.

Lactose. Found in dairy products, like milk, cottage cheese, and thin yogurt.

Fructans. Found in wheat, including many bread products, as well as garlic and onions.

Galacto-oligosaccharides. Typically found in beans.

Polyols. Found in mushrooms and peaches, and in artificial sweeteners like sorbitol, mannitol, and xylitol.

The Low-FODMAP Diet

Formalized in 2010, the low-FODMAP diet was developed by a team of researchers at Monash University in Australia. They found that removing foods with the highest concentrations of FODMAPs from the diet improves IBS symptoms. A low-FODMAP diet can also help people with other ailments, like small intestinal bacterial overgrowth (SIBO) and in some cases Crohn’s disease and ulcerative colitis. This is specifically when they are in remission and have IBS symptoms.

The diet, which should be followed under the guidance of a registered dietitian, involves eliminating FODMAP-containing foods for two to eight weeks, depending on the person and the severity of their symptoms. Once all GI distress has disappeared, the person slowly adds the foods back to their diet to determine the level they can handle before IBS symptoms start to return.

There are many different ways to accomplish this “reintroduction process.” I have found it most helpful to eat a small amount of food in one FODMAP category once a day for three days, while observing how the body reacts. This method isolates each sugar and will show clearly how your body reacts to it.

For example, if you eat a couple of teaspoons of honey once a day for three days and find you are perfectly fine, you have passed the fructose “test.” You would then take fructose back out of your diet and go on to lactose. (You remove the category of food you have tested to avoid building up these sugars.) If you have a negative reaction, you would take that category back out of your diet, give yourself a few days without any FODMAPs, then go on to the next category.

This system helps empower people by teaching them which foods make them feel better or worse. They can then decide how and when they want to manage their symptoms. For instance, if ice cream upsets your stomach, you might choose to avoid it during the week because you want to focus on your job and avoid stomach rumblings during meetings. While on weekends, you may not worry about that and decide to have a scoop.

The Low-FODMAP Diet Is Not Forever

We do not know the long-term effects of adhering to this restrictive diet, but we do know you should not stay on it indefinitely. It is healthier to have some FODMAPs in our diet because fermentable carbohydrates are necessary to provide energy to the “good” bacteria in our colon.

Keep in mind that people with IBS are not allergic to these foods—they are intolerant of them at varying levels. It is important to determine how much of the problematic food types you can tolerate by retesting them in smaller amounts. If fructans trigger your IBS symptoms, say, you might still be able to eat a small amount without reacting. So instead of cutting out garlic entirely when cooking, use the level you can tolerate, which might be a half or quarter clove.

Also, try to avoid consuming multiple FODMAPs all at once, because the cumulative effect can be challenging. Monash University offers a helpful app that uses a “traffic light” system to indicate whether a food is considered low, moderate, or high in FODMAPs.

Keys to Success

The diet takes time and patience, and you need to be very organized. Having the right information is critical. There is a lot of FODMAP data on the internet, but some of it is incorrect or outdated. The diet is constantly being updated, with researchers continuing to test different foods, and adding items to the list of tolerable and intolerable foods. While on this diet, it is also important to make sure you are still getting all the essential nutrients, as well as plenty of fiber. These are all reasons it is important to work with a registered dietitian (RD) who is well versed on the low-FODMAP diet and can help you follow it in the most effective and healthy way.

As an RD in gastroenterology, I have seen how difficult living with IBS can be. But I have also seen how managing the disease by changing how one eats has been incredibly helpful—even life-changing—for many people.