The lowdown on the low-FODMAP diet

Irritable bowel syndrome (IBS) is a common intestinal disorder that produces distressing symptoms like abdominal pain, significant bloating, and altered bowel movements that can shuttle between diarrhea and constipation.

While changing what you eat won’t cure you, an evidence-based approach called the low-FODMAP diet is the most frequently prescribed food plan to help relieve IBS symptoms. Studies show it can reduce symptoms for the majority of patients. However, because of certain challenges and risks associated with the low-FODMAP diet, it’s worth talking to an expert before you try it.

FODMAP basics

 The low-FODMAP diet addresses four types of fermentable carbohydrates: oligosaccharides, disaccharides, monosaccharides, and polyols (collectively referred to as FODMAPs). While the names sound somewhat abstract, the foods found within these groups are often too familiar to those with digestive woes.

Oligosaccharides are present in foods like wheat, beans, garlic, and onions, while the disaccharide lactose is prevalent in dairy products like ice cream and milk. Monosaccharides refer to foods with excess fructose, and are found in items like apples, mangos, and honey. The final group, sugar alcohols, are found in some artificially sweetened products like chewing gum, and are naturally present in foods like avocados and mushrooms.

Though the FODMAP carbohydrates can trigger digestive discomfort for anyone when consumed in large amounts, much smaller portions can worsen symptoms for those with IBS.

A multiphase approach to a low-FODMAP diet

The low-FODMAP diet is meant to be undertaken in three phases. In the first phase, all high-FODMAP foods are eliminated from the diet for an extended period of time, often four to six weeks. In phase two, you systematically reintroduce restricted foods, noting how well you tolerate increasing quantities of the foods you’re reintroducing. Phase three is the personalization phase, in which you only avoid foods in quantities that cause symptoms.

This multiphase process can be complex and confusing, and requires substantial food knowledge. For instance, most varieties of soymilk are high-FODMAP. Extra-firm tofu, on the other hand, while also made from soybeans, is low-FODMAP. Guidance from a dietitian can be helpful for navigating this diet, but insurance coverage and medical referrals can be barriers to scheduling an appointment. As a result, some patients simply receive a list of low- and high-FODMAP foods.

Risks associated with not reintroducing some high-FODMAP foods

While avoiding high-FODMAP foods can be difficult, adding the carbohydrate groups back systematically to test tolerance can be even more challenging. Some people become hesitant to reintroduce items, especially if they have experienced significant symptom relief during the elimination phase. This increases the potential for nutritional risks. For example, it’s common for people avoiding dairy to have inadequate calcium intake.

Other lesser-known nutrients, like magnesium, are also a concern. Some of the best dietary sources of magnesium come from beans and nuts like almonds and cashews, which are usually restricted during the initial phase of the diet. In addition, people with IBS may already be at increased risk of magnesium deficiency due to digestive symptoms like diarrhea.

There is also concern that long-term restriction of high-FODMAP foods changes the makeup of bacterial colonies in the gut, which may negatively impact intestinal health and possibly worsen digestive issues over time. Oligosaccharides, in particular, are an important energy source for beneficial bacteria. This is particularly worrisome for individuals with IBS, who have been shown to have lower levels of protective intestinal bacteria and higher levels of potentially harmful inflammatory microbes. Probiotics have been suggested to restore such bacterial imbalances, but this remains contentious, and the American Gastroenterological Association recently published guidelines that recommend their use in IBS only when participating in a research study.

Low-FODMAP is not for everyone

The low-FODMAP diet is not intended for individuals without IBS, nor is it appropriate for everyone with the condition. It should be avoided by anyone with an eating disorder, as it may worsen food fears and diet restrictions. This is particularly notable because those with gastrointestinal issues appear to have a higher prevalence of disordered eating compared to the general population. In addition, people with already restricted diets, such as vegans or those with food allergies, may be unable to meet their nutritional needs on the diet. Those who are already malnourished or underweight are poor candidates, as well. The diet is not as well researched for other gastrointestinal conditions, so it’s generally best to avoid the diet if you don’t have IBS, unless otherwise advised by a doctor or dietitian.

Finding an alternative approach

 If the low-FODMAP diet is not a good option for you, simply cutting back on high-FODMAP foods in your diet, without entirely eliminating any food groups, may be an alternative. If your diet contains many common offenders like garlic, onions, beans, apples, milk, mushrooms, and wheat, a simple reduction may help decrease symptoms.

To find a list of registered dietitians who can help you to safely make changes, click here. Or contact a nutrition practice to ask if they have someone knowledgeable about the low-FODMAP diet.

Related Information: Managing Irritable Bowel Syndrome


  1. Barbara

    I have none of the above mentioned intestinal symptoms but I get a harsh acid/burning feeling in my upper chest that radiates up into my ears for days.
    I cannot eat a large range of foods. My doctor says I have Acid Reflux. I am told it can be temporarily dealt with by medications which over time these meds will deplete bone density which is another big concern for me since I have already had serious bone breaks in last decade.

  2. Jls

    Don’t forgets that polyols are routinely added to many foods and medicines these days including regular chewing gum, mouthwashes, toothpastes, breads, etc. You have to read all labels. I had recurring painful diarrhea more than a decade ago and my go at the time suspected a sensitivity to sorbitol and similar sweeteners. Avoiding those helped me tremendously. I stumbled on Monash on my own and was able to make a few refinements. I never needed to eliminate any foods.

  3. Kay

    My experience with FODMAP diet was also a game changer. I had tried several prescriptions and they did not work for me. My gastroenterologist said she was reluctant about referring me to dietitian because she thinks the diet is complicated. I found it was challenging but not too hard especially after I got an app for my phone for easy reference. I wound up finding out that I’m sensitive to fry tabs and eliminated them from my diet completely for a year. Guess what… my gut issues ceased. I’m now able to tolerate a small amount again with no symptoms!

  4. Bea Toews

    Monash University has an excellent FODMAP App that includes quantities.

    • Mark Holmes

      Fooducate is an app that will also show foods that contain fodmaps. Outstanding app. You do have to pay a bit extra to include the fodmap portion of the app, but well worth it.

    • Anna

      Thank you for your post. I’ve been working with Gastro and a GP who each had theirs own thoughts—but they don’t talk . I’m so happy to see this app’s plan doesn’t completely eliminate food groups and I’ve called GI to clear trial, and I’ve passed on the app info.

    • Lori B

      I agree – the Monash University FODMAP app has been a life saver. It helps guide my choices at the grocery store and restaurants.

  5. Deane Alban

    I tried the FODMAPs diet and it was life-altering. It was challenging at first but now I’ve learned my limits for various foods. I’ve also found over time that I have become more tolerant of certain high FODMAPs foods. And for almost any food I’ve had to give up, I’ve found an acceptable substitute.

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