What is the low FODMAP diet?

By Lou Mudge published 1 day ago

A low FODMAP diet may help to reduce the symptoms of IBS – here’s everything you need to know 

Image shows a variety of low FODMAP foods including peppers, salmon, meat and eggs

(Image credit: Getty Images)

The low FODMAP diet is a diet specifically designed for those with IBS (irritable bowel syndrome) in mind. Those on the diet will go through three phases: Elimination, Reintroduction and Integration, where they will hopefully discover which foods may be triggering their IBS symptoms, and which they can continue to eat going forward without problems. 

The low FODMAP diet cuts out or significantly reduces the consumption of certain sugars, which tend to sit in our digestive systems and ferment as we struggle to digest them. As our gut microbiota break them down, they produce gas, which can cause painful bloating and other uncomfortable symptoms.

IBS affects 7-15% of the general population, with many people experiencing bloating, gas and stomach pain, as well as constipation, diarrhea or a mixture of the two. These symptoms can range from mildly uncomfortable to debilitating, with one person with IBS experiencing the condition differently from the next.

Here, we’ll explain what FODMAPs are, what you can eat on a low FODMAP diet and how you can manage your IBS long term. Plus, find out more about gut health and how to improve your digestion here at LiveScience.

WHAT ARE FODMAPS?

FODMAP stands for ‘Fermentable Oligo-, Di-, Mono-saccharides, And Polyols’, which are short-chain sugars that can trigger symptoms in those with IBS when eaten. 

“FODMAPs are short chains of sugars found in a variety of grains, fruit and vegetables as well as added to some processed foods,” explains Dr Bridgette Wilson, a Doctify(opens in new tab)-reviewed gut specialist and clinical and research dietitian. “The sugars are linked together in such a way that humans may not be able to digest them. These FODMAP sugars are able to be digested by the gut microbes in a process called fermentation, which produces gas as a by-product.”

FODMAPs exist in a wide range of foods, according to a study in the Nutrients (opens in new tab)journal, and people may struggle with properly avoiding them or sufficiently meeting their nutritional requirements while following a low FODMAP diet, so the support of a dietician is vital for success. 

(Image credit: Getty images)

WHAT CAN YOU EAT ON A LOW FODMAP DIET?

Dr Wilson encourages those on the low FODMAP diet to seek expert help, particularly in the restriction phase. “You can eat food from all food groups on a low FODMAP diet, it is important to get specialist advice to help you follow the diet accurately and to maintain a good balance of nutrients while following the restricted phase of the diet,” she says.

Some foods that you can still enjoy on the low FODMAP diet include:

  • Vegetables: Carrots, chives, cucumbers, eggplant, bamboo shoots, spinach, spring onion, ginger, lettuce, parsnips, potatoes and turnips. 
  • Fruits: Lemons, limes, oranges, grapefruit, bananas, strawberries, blueberries, cantaloupe and honeydew melons and kiwi. It is important to note that some of these foods become high FODMAP when under or over ripe, so you should check which stages are ok for you to eat. 
  • Meat and fish: Most unprocessed meat is fine, but beware of processed meats like salami which sometimes contain garlic.
  • Dairy and dairy alternatives: Lactose-free milk, almond milkoat milk, rice milk, coconut milk, lactose-free yogurt, and hard cheeses. 
  • Grains: Oats, rice, gluten-free pasta, quinoa, and corn flour. Check the label of anything listed as ‘gluten-free’ to ensure it doesn’t contain other triggering ingredients. Note: it is not the gluten that you are avoiding on the low FODMAP diet, but the sugars in the wheat. However as gluten-free products are also wheat-free, you can generally eat these. 
(Image credit: Getty Images)

Dr. Tariq Mahmood, Doctor and Medical Director at Concepto Diagnostics(opens in new tab), notes that although the low FODMAP diet may appear restrictive at first glance, it is possible to stay healthy and satisfied while eating low FODMAP. “There are plenty of foods which are totally fine to eat. For example, eggs, fish and meat,” he says. “There are plenty of fruits, grains and vegetables too – grapes, oranges, strawberries, cucumbers, potatoes, tomatoes, oats, quinoa and rice to name but a few. 

“Common beverages like tea and coffee are also fine to drink on a low-FODMAP diet, though not more than three cups per day.”

HOW TO FOLLOW A LOW FODMAP DIET

Dr Mahmood lists some foods to avoid on a low FODMAP diet: “Foods to avoid in excess on a low FODMAP diet include fruits like apples and watermelon, dairy products like fresh and soft cheeses, ice cream and milk, vegetables like broccoli, mushrooms and onions as well as wheat products like biscuits, bread and pasta,” he says. “Then, once you’ve cut out all high-FODMAP foods, you can try to slowly reintroduce them on a one-by-one basis to see which ones do or don’t cause digestive symptoms. 

“Another thing to consider is that as you change your diet, it might be hard to ensure that your body is getting all the nutrients it requires. As such, multivitamins and supplements are your friends. Omega-3, vitamin D, vitamin B6 and calcium are just a handful of the most important vitamins and minerals you’ll need to stay on top of.”

A study in the Journal of Gastroenterology and Hepatology (opens in new tab)encourages people wishing to attempt the low FODMAP diet to do so under the supervision of a dietician. It also recommends that the initial elimination stage lasts no more than 4-6 weeks, as following the diet long term may have negative effects on the gut microbiome.  

STAGES OF THE LOW FODMAP DIET

“The low FODMAP diet is a process of short-term elimination of foods high in fermentable sugars (FODMAPs) followed by a precise reintroduction process to identify the specific group of foods that may be symptom triggers,” explains Dr Wilson. “The final stage of this process is personalisation where the diet is expanded to include all the FODMAP food that are not triggers,”  

Elimination

In this phase, all high FODMAP foods are cut out for a period of 4-6 weeks. The elimination guide produced by Monash University(opens in new tab) (where the low FODMAP diet was developed) reminds us that the low FODMAP diet is not an elimination diet, but a substitution diet. While it may seem difficult to swap out foods with very distinct flavors like onions and garlic, a dietician can signpost you to low FODMAP alternatives, such as chives or garlic infused oil, which can make this phase easier.  

Reintroduction

Reintroduction involves strategically testing out each FODMAP sub-group (fructose, lactose, sorbitol, mannitol, fructans and galactans) to see if you can digest them without experiencing symptoms. You will maintain the low FODMAP diet in the background and test each sub-group individually and in increasing amounts over a few days, with a break of a couple of days before trying a new reintroduction. You may find that you can tolerate some foods in small amounts, while others can be completely integrated into your diet without restriction. It is important to have a dietician’s support for this stage, as they will be able to give you advice on which foods are the best to test your tolerance of each sub-group. 

Integration/personalization 

In the integration phase, you work with your dietician to take the results of the reintroduction phase and apply them to your diet. If some FODMAPs still trigger you after elimination, these will be avoided going forward, but you can test your tolerance every few months as our response to FODMAPs tends to change over time.

These 5 ways to improve gut health might offer some tips to help with your gut health after the integration phase. 

BENEFITS OF A LOW FODMAP DIET

According to Dr. Mahmood, “digestive issues are also linked with anxiety, depression and stress as well, making a low-FODMAP diet worthwhile if you struggle with IBS”.

He also says that avoiding all FODMAPs is a serious challenge that borders on impossible, as some of the most common FODMAPs include fructose (found in most fruits and vegetables), fructans (found in grains) and lactose (found in dairy products). However, research has shown that bloating, pain and passing wind also were reduced in IBS patients who were on a low-FODMAP diet.

A study in the Nutrients(opens in new tab) journal also found that the low FODMAP diet significantly reduced bloating and pain in subjects. As these are two of the main symptoms of IBS, cutting out foods that are responsible for these symptoms might help to lift some of the burden of IBS.

The low FODMAP diet is clinically proven to provide significant decrease in IBS symptoms,” adds Dr Wilson. “It is a process of identifying specific food triggers of IBS symptoms. By knowing exactly what foods are triggers, people with IBS can regain confidence with food, freeing them from food and social anxiety.”

Lou Mudge  Health Writer

Lou Mudge is a health writer based in Bath, United Kingdom for Future PLC. She holds an undergraduate degree in creative writing from Bath Spa University, and her work has appeared in Live Science, Tom’s Guide, Fit & Well, Coach, T3, and Tech Radar, among others. She regularly writes about health and fitness-related topics such as air quality, gut health, diet and nutrition and the impacts these things have on our lives. 

She has worked for the University of Bath on a chemistry research project and produced a short book in collaboration with the department of education at Bath Spa University.