Jack Harley, Therapeutic Neuroscience at Oxford University
reviewed by Dr Michael Yapko
Wednesday, September 16, 2020
Jack Harley, Therapeutic Neuroscience at Oxford University
Wednesday, September 16, 2020

The low FODMAP Diet: Best diet for IBS?


If you have IBS, you’ve probably wondered “is there a scientifically-proven diet to improve my symptoms?” We’re here to tell you that, yes, there is! The low FODMAP diet has been shown in numerous studies to improve symptoms such as bloating, constipation, diarrhea and abdominal pain for people with IBS.

Low FODMAP diet eliminates, then slowly reintroduces, hard to digest types of carbohydrates that can cause gut symptoms. This type of elimination diet may be helpful, so long as you keep track of what you eat and flex your willpower to avoid triggering high FODMAP foods.

Read on to find out all about the low FODMAP diet and how to follow the food elimination regime (including a low FODMAP diet PDF!). 

What is IBS?

Irritable bowel syndrome (IBS) is a pattern of digestive problems. IBS is a medical condition, however, it isn’t caused by a particular disease or damage to the digestive tract. 

While IBS doesn’t typically do any lasting damage to bowels or intestines, it can be uncomfortable, painful, and may affect many aspects of your daily life. 

Common symptoms of IBS include:

The exact cause of IBS is unknown and there is no cure. However, many treatments, such as dietary change, stress management, and alternative therapies, like hypnotherapy, can help people to manage their symptoms. 

What are FODMAPs?

FODMAPs are Fermentable Oligosaccharides, Disaccharides, Monosaccharides, and Polyols—which are all scientific names for several poorly digested carbohydrates. 

High FODMAPs can be found in many everyday foods, including some you may have thought were “IBS-safe”, like watermelon.

FODMAP food definitions include:

  • Oligosaccharides: these are complex carbohydrates. They are found in various fruits and vegetables, such as garlic and onions.
  • Disaccharides: these are double-unit sugars. They are in lactose products, such as milk, yogurt, and soft cheeses.
  • Monosaccharides: these are single-unit sugars, such as fructose. These types of sugars are found in various fruits including figs and mangoes, and sweeteners such as honey. 
  • Polyols: these are sugars found in certain fruits and vegetables including blackberries, as well as some sweeteners like those in chewing gum.

Eating FODMAPS increases the amount of gas in the intestines. This is because high FODMAP foods ferment more quickly in the gut than non-FODMAPs and release gas as a byproduct. This can lead to IBS symptoms such as abdominal pain and bloating

FODMAPS can also cause diarrhea and other IBS symptoms. This is because high FODMAP molecules cause the body to draw more fluid into the bowels.

The International Foundation for Gastrointestinal Disorders notes that FODMAPs have the same digestive effects for most people, however, it’s only those with more sensitive or easily irritated bowels that experience problematic gut symptoms.

Which foods are high in FODMAPs?

The following foods are high in FODMAPs and should be avoided on a low FODMAP diet:

  • Fruits: including apples, mangoes, pears, plums, watermelon, canned fruit, peaches, cherries
  • Vegetables: including celery, cauliflower, onions, garlic, leeks, mushrooms, snow peas, peas, okra
  • Grains: including wheat, barley, couscous, rye, semolina
  • Lactose-containing foods: including cow’s milk, soft cheeses, ice cream, custard, cream
  • Legumes: including soybeans, black beans, lentils, chickpeas, kidney beans, butter beans
  • Sweeteners: including sorbitol, high fructose corn syrup, fructose, honey, mannitol
  • Nuts: including cashews and pistachios

Which foods are low FODMAPs?

The following foods have been identified as being low in FODMAPS and are allowed on a low FODMAP diet. These include:

  • Fruits: including banana, blueberry, kiwi, lemon, lime, pineapple, strawberry, grapes
  • Vegetables: including broccoli, carrots, bok choy, eggplant, green beans, kale, lettuce, tomato, corn
  • Grains: including brown rice, quinoa, oats, gluten-free products
  • Sweeteners: including sugar (sucrose), maple syrup, glucose, brown sugar
  • Dairy substitutes: including almond milk, rice milk, coconut milk, lactose-free kinds of milk and yogurts
  • Nuts: including almonds, pecans, pine nuts, brazil nuts, walnuts, macadamia nuts
  • Protein sources: including beef, lamb, pork, chicken, eggs, fish, turkey
Double-click to download the Low FODMAP Diet PDF

How to start a low FODMAP diet

Some people mistakenly think that low FODMAP diets function like ketogenic diets, where certain foods are avoided for long periods of time (even years). However, low FODMAP diets are designed to be completed in short stages, whereby some foods are removed from the diet before being slowly reintroduced. 

The low FODMAP diet involves three steps:

  1. Elimination: first, high FODMAP foods are removed from the diet. This phase generally lasts 3 to 8 weeks. 
  2. Reintroduction: once symptoms have improved, troublesome foods are slowly reintroduced, one at a time and symptoms are monitored. 
  3. Maintenance: you resume a normal diet, limiting only the FODMAP foods that cause symptoms. Some people may eventually be able to add many FODMAPs back into their diet without symptoms.

What does Science say about the low FODMAP diet?

Numerous clinical trials have found the low FODMAP diet can help people improve their IBS symptoms. 

In a recent Australia study, 38 people with IBS were randomly assigned to follow either a low FODMAP diet or a typical Australian diet for three weeks. This was followed by a period of normal eating before participants switched to the alternate diet for another three weeks. Overall symptoms of IBS were reduced by 50% on the low FODMAP diet.

Another study comparing typical healthy eating to a low FODMAP diet for people with IBS showed that significantly more people following a low FODMAP saw improvements in bloating, abdominal pain, and flatulence.

Studies also show that IBS symptoms stay improved for a long time (around 6 months) after reducing FODMAPs and even after reintroducing them. However, people should continue to avoid the FODMAP foods that trigger their symptoms.

Should I consult a healthcare professional before starting a low FODMAP diet?

The low FODMAP diet can be confusing—there are many different foods you need to track and avoid. It is generally recommended you seek advice from a dietitian or a healthcare professional before starting the diet. 

A dietician or a healthcare professional can help understand the theory behind the diet, outline suitable foods, and provide you with personalized advice.

If you want to start the diet by yourself, there are many online resources, including the Monash University Low FODMAP app, that can help you along the way. 

However, low FODMAP diets are complicated and may affect your nutritional intake, so you should talk to a healthcare professional before getting started.

What are the possible health risks of a low FODMAP diet?

In general, the low FODMAP diet is not recommended as a permanent IBS solution. Some of the possible risks & side-effects of following a restrictive low FODMAP diet include: 

1. Nutritional deficiencies

Because a low FODMAP diet cuts out many fruits and vegetables and there is the potential for inadequate nutrient intake.

You may need to take vitamin and mineral supplements while on a low FODMAP diet. In particular, it is important that you get enough calcium, iron, zinc and folate intake, and fiber consumption, even if you’re cutting out common foods like dairy. 

Because a low FODMAP can affect a person’s nutritional intake, it’s not generally recommended during pregnancy, for people who are underweight, or for people with eating disorders.

2. Disordered eating

There are also risks of becoming disordered in your eating habits after following a restrictive low FODMAP diet. A recent study of over 200 people with IBS showed that those who closely followed the low FODMAP diet showed eating disorder behaviors.

3. Disrupting healthy gut bacteria

Probiotics are ‘friendly’ bacteria that can improve gut function. Several studies have shown probiotics can improve IBS symptoms such as bloating, pain, and constipation. However, a low FODMAP diet may disrupt your natural gut flora. 

One study showed the low FODMAP diet lowered the abundance of ‘good’ bacteria including Bifidobacteria and Lachnospiraceae. So, if you’re planning on completing a low-FODMAP diet, make sure you boost health-promoting bacteria with low FODMAP probiotic foods, such as Lactose-free Kefir or Greek yogurt.

Alternatives to a low-FODMAP diet 

If you’re looking for a way to manage your IBS without restricting your diet, there are many management strategies available that might work for you, such as cognitive-behavioral therapy, meditation, or yoga

Another IBS management option that’s been proven to be as effective as a low-FODMAP diet is gut-directed hypnotherapy. 

A recent study indicated that gut-directed hypnotherapy was as effective as the low-FODMAP diet in improving IBS, and was shown to reduce symptoms by up to 70%.

Gut-directed hypnotherapy is a simpler option for many people and can usually calm symptoms within six weeks, without the need for complicated food tracking or diet restrictions.

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Can I still go out to eat on a low FODMAP diet?

Many meals contain FODMAPs so eating out on the diet can be challenging. However, if you’re looking for a special meal on the town, there are some things you can do to avoid triggering FODMAP foods. Some tips include:

  •  Café: order your tea or coffee with lactose-free milk or almond milk. Choose sandwiches made with gluten-free bread.
  •  Pub food: choose plain meat, fish or chicken without marinade, and a side of low FODMAP salad or fries.
  • Asian cuisine: choose fried rice or a stir fry with no onion or garlic. Sushi and sashimi are also acceptable options.
  • Italian: choose gluten-free pasta and request a sauce that does not contain onion or garlic.

Can I do the low FODMAP diet as a vegetarian?

It is possible to do the low FODMAP diet as a vegetarian, however, it may pose some nutritional challenges as many staple protein sources, like beans and yogurt, are high in FODMAPs.

If you want to try a low FODMAP diet, without giving up important vegetarian protein sources, you may want to include more of these low FODMAP/high protein foods in your diet:

  • Tempeh
  • Pecans, pine nuts, walnuts
  • Eggs
  • Lactose-free milk
  • Seeds like chia, flax, hemp, pumpkin
  • Peanut butter

Can I cook with FODMAP foods and remove them later?

It might seem like a smart solution to cook with onions and garlic then remove them from a sauce or soup later—but this isn’t an effective way to avoid high FODMAPS.

Almost all FODMAPs dissolve in water. So, if you are cooking with high FODMAP foods in a soup or a sauce, the FODMAPs will leach out from the high FODMAP foods into the entire dish. While it may be frustrating, it’s best to avoid cooking with high FODMAP foods entirely while on a low FODMAP diet. 

Can a low FODMAP diet be flavorful?

Because a low FODMAP diet restricts onions and garlic, many people might think that diet will mean weeks of boring, flavorless meals. 

And yes, while many tasty recipes rely on high FODMAP ingredients, there are also many low FODMAP herbs, spices, and flavorings that can add zest to your dishes. Try including these low FODMAP flavor substitutes:

  • Chili
  • Mustard
  • Saffron
  • Turmeric
  • Ginger

Should I start a low FODMAP diet?

Before starting a low FODMAP diet, you should have your doctor confirm you have IBS using the official diagnostic criteria

Generally, a healthcare professional will check that you experience all three of the following to give you an IBS diagnosis. 

  • Abdominal pain: for at least one day per week in the past three months.
  • Changes in your stools: either in appearance or frequency.
  • Long-term symptoms: symptoms must have persisted for more than 6 months.

You may also want to consider whether a low FODMAP diet is right for you and your lifestyle. If you have trouble sticking to complicated diets or don’t want to give up certain foods or social activities that involve food, then you may want to look into alternative IBS treatments. 

The Wrap Up

The low FODMAP diet is one of the best diets for improving IBS. This diet removes carbohydrates known to trigger symptoms of IBS then slowly reintroduces them over time. This diet can help you maintain better gut health long-term, however, there are some potential risks and lifestyle issues you may want to consider before getting started. If a restrictive diet isn’t right for you, you may want to try gut-directed hypnotherapy, which has been shown to be as effective as a low FODMAP diet in reducing IBS symptoms. Before starting a low FODMAP diet, talk to a healthcare professional to get an official IBS diagnosis.

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Our Sources

Mindset Health only uses high-quality sources, including peer-reviewed research, to support our articles. We work with experts to ensure our content is helpful, accurate and trustworthy.

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