FODMAP foods are foods that contain certain types of carbohydrates. They include sugars that can cause symptoms in the digestive systems of susceptible individuals. Studies have shown eating a diet low in FODMAP-containing foods may reduce symptoms of irritable bowel syndrome and other gastrointestinal conditions.

FODMAP stands for “fermentable oligosaccharides, disaccharides, monosaccharides, and polyols.” Low FODMAP foods are low in these substances.

Irritable bowel syndrome (IBS) is a gastrointestinal disorder that affects 10–15% of adults in the United States, although only 5–7% of adults have received a diagnosis, according to the American College of Gastroenterology. It involves gastrointestinal symptoms, including bloating, diarrhea, and constipation.

The low FODMAP diet may also benefit people with inflammatory bowel disease, which includes Crohn’s disease and ulcerative colitis. A 2020 study found, for example, that the diet had a favorable impact on symptoms in people with Crohn’s disease. It may also help those with celiac disease.

The low FODMAP diet is not a long-term diet plan but a way to identify and substitute specific foods that may worsen symptoms. Experts do not recommend following this diet for more than 6 weeks due to the risk of nutritional deficiencies.

In this article, we look at the benefits of a low FODMAP diet, how one works, and what the research says.

A team of researchers from Monash University in Melbourne, Australia, developed The Low FODMAP Diet. The group was the first to prove that low FODMAP diets improved IBS symptoms.

The diet plan classifies FODMAP foods as high and low. It recommends that people with IBS avoid high FODMAP foods and choose low FODMAP foods as their daily staples.

It is important to note that serving sizes can also change how well a person tolerates a specific food. For example, having a large amount of a low FODMAP food could turn it into a high FODMAP food.

Originally, the diet was somewhat restrictive, raising concerns about nutritional deficiencies and disordered eating. Many dietitians now take the approach of a FODMAP-gentle rather than a FOPMAP-free diet. Experts recommend working with a dietitian to avoid both over-restriction and under-restriction.

Protein foods such as meats, poultry, and fish are naturally free of FODMAPs. Some processed and marinated meats may contain high FODMAP ingredients, such as garlic and onion, but not all meat products contain these ingredients. People should discuss their choices with a dietitian.

Low FODMAP foods, which people can eat more liberally than medium and high FODMAP foods, include:

  • Vegetables: Lettuces, carrot, chives, fennel, eggplant, broccoli (heads or whole), zucchini, green beans, and baby spinach.
  • Fruits: Strawberries, pineapple, grapes, oranges, cucumbers, and kiwifruit.
  • Proteins: Chicken, beef, turkey, cold cuts, lamb, tofu, and eggs.
  • Fish: Crab, lobster, salmon, tuna, and shrimp.
  • Fats: Oils, pumpkin seeds, butter, peanuts, macadamias, and walnuts.
  • Starches, cereals, and grains: Potatoes, amaranth, quinoa, brown rice, tortilla chips, and popcorn.

High FODMAP foods to avoid or limit include:

  • Vegetables: Garlic, asparagus, onions, mushrooms, beans, shallots, and scallions.
  • Fruits: Blackberries, watermelon, prunes, peaches, dates, and avocados.
  • Meats: Breaded meats, battered meats, and meats served with garlic or onion-based sauces and fillings.
  • Fish: Breaded fish, battered fish, and fish served with garlic or onion-based sauces.
  • Fats: Almonds, cashews, pistachios, and avocados.
  • Starches, cereals, and grains: Beans, lentils, wheat and gluten-based bread, rye, muffins, pastries, and pasta.

Knowing the difference between high and low FODMAP foods can make it easier for a person to incorporate them into a diet. Both categories contain a wide range of food groups.

It is essential to talk with a doctor or dietitian before starting a low FODMAP diet. Doctors do not typically recommend this diet plan for long-term use, as it eliminates some essential, nutrient-rich foods.

Many foods high or moderate in FODMAPs contain a number of nutrients, including vitamins, minerals, and prebiotics, which are food components that support healthy gut bacteria.

Symptoms that may improve after following the diet include:

  • abdominal pain
  • bloating
  • diarrhea

Read about different coping strategies for IBS.

Here is an example diet plan for one day on a low FODMAP diet:

  • Breakfast: egg and spinach scramble with chives
  • Lunch: tuna salad with lettuce, carrots, and cucumber
  • Snack: popcorn or a handful of walnuts
  • Dinner: tofu stir fry with zucchini, broccoli, and brown rice

It is important to note that low FODMAP diets are restrictive and should be temporary, lasting only 4–6 weeks. They aim to identify whether specific foods trigger symptoms.

A low FODMAP diet involves three phases. Monash University, which first proposed the diet, describes them as follows:

  • Step 1: Low FODMAP: In this phase, the person swaps all high FODMAP foods for low FODMAP options for 2–6 weeks. Some people call this the elimination phase, but Monash stresses that it is a case of substitution rather than elimination.
  • Step 2: Reintroduction: Under the guidance of a registered dietitian, the person starts reintroducing FODMAP foods into their diet one at a time. This can help identify which foods trigger symptoms. This phase lasts around 6–8 weeks.
  • Step 3: Personalization: Also known as the maintenance phase, this involves returning to a regular diet as far as possible, limiting only the FODMAP foods that cause IBS symptoms. Eventually, some people may be able to incorporate all or most FODMAPs back into their diet without symptoms.

It is essential to reintroduce foods to see if they cause symptoms, because the aim of the diet is to eliminate only those foods that are troublesome.

Useful resources for information about low FODMAP diets and specific foods to include and limit in a low FODMAP diet are the International Foundation for Gastrointestinal Disorders and the Monash University app.

Many other sites provide low FODMAP recipes and tips.

Several studies support low FODMAP diets for managing IBS symptoms, but there is also some controversy.

A 2017 review concluded that low FODMAP diets can help manage IBS symptoms, but it did not find a low FODMAP diet to be more effective than other diet plans for IBS.

Meanwhile, some experts have warned that the diet may not be beneficial for everyone with IBS. Possible drawbacks include the following:

  • It can be hard to understand, learn, and follow.
  • It is a restrictive diet that could increase the risk of disordered eating in some people.
  • As a restrictive diet, it could also be hard to follow over time.
  • Incorrect use could lead to problems such as nutritional deficiencies and changes to the gut microbiota.
  • A lack of standardization of both what the diet involves and food labelling can lead to confusion.
  • It may be costly.
  • It could worsen some symptoms, such as constipation.

Overall, most researchers seem to agree that, for people with IBS:

  • A low FODMAP diet may be beneficial in some cases.
  • It is essential to follow the diet with the guidance of a medical professional, as there are some risks.
  • More research is needed to identify the best way to follow the diet and how effective it might be.

In 2020, some experts concluded that a low FODMAP diet could manage symptoms of IBS, other gastrointestinal diseases, and possibly some conditions not relating to the digestive system. But they insisted that people should follow it with caution and only with the guidance of a medical professional.

One 2021 review concluded that the low FODMAP diet reduces gastrointestinal symptoms and improves quality of life in people with IBS, compared with other diets. But the researchers noted that more work is needed to know more about how this type of diet can affect a person in the long term in terms of getting the nutrients they need and the health of the gut microbiome.

The authors of another 2021 review concluded that a low FODMAP diet can help reduce symptoms and improve bowel habits in adults with IBS, and especially those with IBS-D, where diarrhea is a dominant symptom.

Research on the use of the low FODMAP diet for IBS is ongoing. While some studies have found that a low FODMAP diet may help reduce symptoms in some people with IBS and other gastrointestinal disorders, this diet may not be effective or appropriate for everyone with IBS or other conditions that impact the digestive tract.

Two symptoms of IBS are constipation and diarrhea.

Some evidence suggests a low FODMAP diet may help reduce constipation in people with IBS, but the picture is likely more complex.

For most people, doctors recommend a high fiber diet to help prevent constipation. Fiber helps food move through the digestive system and encourages the transfer of fluid into the gut, which helps keep stool soft.

Avoiding high FODMAP foods and not replacing them with suitable alternatives could increase the risk of constipation in a person with IBS. Experts recommend working with a dietitian while progressing with the diet to ensure the correct balance and type of fiber to prevent constipation.

A 2021 review notes that a low FODMAP diet may be more helpful for people with IBS where diarrhea is the dominant symptom.

Researchers are still studying how a low FODMAP diet can affect constipation that occurs with IBS.

Even though following a low FODMAP diet may lead to weight loss in some people, healthcare professionals do not recommend it as a weight loss diet.

Some of the weight loss seen in people following the low FODMAP diet could be due to insufficient calorie intake. This could lead to negative health outcomes, especially if a person has a low weight at the start.

Anyone who is keen to lose weight should speak with their doctor, who will help them find a suitable option.

Here, find some tips for losing weight.

A low FODMAP diet may help improve symptoms of IBS and other digestive conditions. But its effectiveness may depend on various factors, such as the symptoms a person has and how they follow the diet.

Anyone interested in starting a low FODMAP diet should talk with their doctor or a dietitian regarding the benefits and risks and work with them to make a plan that will help the individual manage symptoms while maintaining a balanced diet.