The low FODMAP diet was designed by researchers from Monash University in Melbourne, Australia. It has revolutionized the management of IBS with 70% of those with IBS trialing the diet finding it relieves their symptoms.
What is IBS?
Irritable bowel syndrome (IBS) is a gut disorder that typically presents with abdominal pain, constipation, diarrhea, bloating, flatulence and/or reflux.
Whilst it is hard to have exact numbers, it is estimated that 10-20 out of 100 people have IBS. It typically develops between the ages of 20 and 30 and is twice as common in women.
Symptoms are different for everyone and can also change over time.
IBS is not a dangerous condition, and many people will only have mild symptoms which they may choose to not seek treatment for.
For others, IBS can have a huge impact on quality of life and symptom management is a high priority.
Unfortunately, IBS is not “curable”, so symptom management is the only option.
It is also a chronic condition meaning that although it can have periods of no or mild symptoms and periods of more severe symptoms, it is always underlying.
What causes IBS?
The causes of IBS are not well understood. However, there are some theories that could explain why IBS occurs.
These theories include over sensitive nerves in the intestines, inflammation of areas of the gut and intestinal mucosal disorders.
People that have had an intestinal infection with a fever and severe diarrhea are more likely to develop IBS later in life.
IBS can potentially be inherited through genetics as well.
How is IBS diagnosed?
There is no specific diagnostic tool for IBS. It is more or so done as a process of elimination. When you present with gut symptoms, your doctor will want to cross all other possibilities off the list before diagnosing you with IBS.
Disorders that they will be checking off their list include:
- Coeliac disease
- Inflammatory bowel disease (IBD) – which can either be ulcerative colitis or Crohn’s Disease
- Diverticulitis – infection or inflammation of pouches in the bowel wall
Depending on your symptoms, they may also check for
- Gallstones (severe abdominal pain)
- Bowel cancer (blood in stool)
To be diagnosed with IBS, you also need to meet the following criteria:
Associated with recurrent abdominal pain ≥1 day/wk in the last 3 months (on average) and must have ≥2 of the following:
1) Related to defecation (either increasing or improving pain)
2) a change in stool frequency
3) an associated change in stool form (appearance)
Strategies to try before a low FODMAP diet
Let’s say that all other possibilities have been assessed and your symptoms are very likely the result of IBS.
The low FODMAP diet is not an easy process nor is it a quick one. So sometimes it can be beneficial to try a couple of other avenues before taking on the burden of the low FODMAP diet.
You could try any of the following lifestyle and dietary changes that you feel are applicable to you and may assist with symptom management.
Improve the overall quality of your diet
- Eat regular meals and snacks to avoid very large portions in single sittings
- Include at least eight cups of water or non-caffeinated fluids per day particularly if you are trying to manage constipation
- Make home-cooked food with a focus on fruits, vegetables and wholegrains and avoid fatty, take out food too often
- Limit alcohol intake to no more than two standard drinks per day, with two alcohol-free days per week
- Ensure that your fibre intake is adequate (>25g daily)
- If following a plant-based diet, your fibre intake may even be too high and start to cause symptoms in which case you could limit your intake to 25-35g per day
For some people it may even help to
- Limit caffeine intake
- Minimise intake of soft drinks and other carbonated drinks
- Limit intake of spicy food
Make some lifestyle changes
- Take your time when eating meals – sit down, eat slowly and chew your food well.
- Exercise regularly. Keeping your body moving can improve gut symptoms in some people.
- Your mood and stress levels can affect your gut and bowel habits. Take some time during your day to do an activity that helps you relax or de-stress.
Managing specific symptoms
Bloating & wind
- Reduce gas-producing foods such as legumes, cruciferous vegetables, sugar-free mints/chewing gum & carbonated beverages.
- Try adding flaxseeds/linseeds (up to one tablespoon/day – start small and build up) to your diet
- Avoid eating quickly, eating with your mouth open or chewing gum. This will minimise the amount of air you swallow.
- Limit caffeine intake
- Minimise or exclude sugar-free or diet products that contain sorbitol, mannitol and xylitol
- Limit fatty foods as these can sometimes worsen symptoms
- Increase intake of soluble fibre such as bananas, oats and oat bran, barley, chia seeds, psyllium (Metamucil) & Benefiber
- Drink adequate fluids throughout the day
- Include a wide variety of high fibre foods in your diet. You should add these foods gradually as you may get more symptoms if you increase these foods too quickly.
- Exercise regularly
Some other constipation specific nutrition tips can be found in another article I have written on the topic.
A quick word on probiotics
Some people find their symptoms are dramatically improved through the use of probiotics. If you do decide to trial them, take one product consistently for four weeks. If there is no improvement stop or try another type of probiotic.
You can also add more probiotic rich foods into your diet such as yogurt & pickled vegetables.
Keeping a Food & Symptom Diary
Before trialling a low FODMAP diet, you may also want to consider keeping a food and symptom diary.
Write down the foods you eat and the symptoms you experience for a week or two to see which foods are helping or worsening your symptoms. You could also keep note of exercise, stress levels as well as fluid intake.
Food diaries can be a great way to easily isolate your individual dietary and lifestyle triggers.
On the other hand, the triggers or IBS symptoms may not always be easy to isolate or you may be triggered by a vast array of foods, in which case a low FODMAP diet would be the correct route to take.
What are FODMAPs?
Alright, so you have eliminated all other possible causes of your gut symptoms, you have tried a few dietary and lifestyle changes that were applicable to you and even kept a food and symptom diary, but you still have not clearly identified what causes your symptoms.
FODMAPs are short-chain carbohydrates which ferment in your large bowel and are poorly digested. This results in many common symptoms of IBS including bloating, pain, and abdominal distention. As the fermentation process draws in water and produces carbon dioxide, hydrogen, and/or methane gas.
The acronym FODMAP stands for:
● Fermentable – these types of compounds are broken down (fermented) by bacteria in the large intestine which produces gas
● Oligosaccharides (fructans & GOS) – “oligo” means “few” and “saccharide” means sugar. These molecules are made up of individual sugars joined together in a chain
● Disaccharides (lactose) – “di” means two. This is a double sugar molecule
● Monosaccharides (fructose) – “mono” means single. This is a single sugar molecule
● And Polyols (sorbitol & mannitol) – these are naturally occurring and man-made sugar alcohols
FODMAPs are not well digested by anybody but most people will not experience symptoms. Those with IBS, however, can have a range of symptoms from consuming various FODMAP groups.
With IBS, you may find you react to some FODMAP groups but not others and/or that your tolerance varies between groups.
How does the low FODMAP diet work?
The low FODMAP diet works in 3 stages.
The first stage is the elimination of FODMAPs from the diet. This can actually be very difficult since a whole range of foods contain FODMAPs in varying quantities.
If you are eating a diet with plant based foods (which you definitely should be), it is impossible to have a no FODMAP diet.
The aim of the game is simply to limit FODMAP consumption to below a certain level by only consuming low FODMAP foods and avoiding ones that are moderate to high in FODMAPs.
The trickiest part of this beyond knowing which foods are high versus low FODMAP, is that the quantity of FODMAPs in a food is dependent on the quantity of that food you are consuming.
For example, green beans are a low FODMAP food when the quantity consumed is <75g. However, over 175g of green beans is a high FODMAP portion.
What if symptoms persist?
If you have not seen a significant improvement in your symptoms following the low FODMAP diet:
- You may not have been doing it strictly enough or are still consuming higher FODMAP foods unknowingly
- OR FODMAPs may not be the issue – in which case you should cease the diet and move onto alternative management options. It would be best to discuss these with a doctor or dietitian on a case by case basis.
What if you start to see results?
If you have seen a significant improvement in symptoms you should continue the low FODMAP diet and proceed to step two.
The second stage of the low FODMAP diet, is the reintroduction phase.
During this process you will keep your diet low FODMAP except for your challenge foods.
Each FODMAP subgroup will be challenged separately to distinguish which groups are a particular problem for you and what your individual tolerance is.
Once we have this information, you can proceed to stage three.
Stage 3 is the liberation from the low FODMAP diet. You will introduce all of the foods that went well during the challenge phase back into your diet.
The diet you end up with at the end of the process is not a low FODMAP diet, but is personalised to you so you can limit the foods that cause symptoms and continue eating all the great high FODMAP foods that don’t.
The liberation and personalisation stage of the low FODMAP diet is often ignored, however, it is a really important aspect of the process.
Being on a low FODMAP diet for an extended period of time is very restrictive, which can also have implications for your overall nutrient intake.
Also, since FODMAPs are important for maintaining a healthy gut microbiome, it is typically a good idea to reintroduce as many of them as you can without noticeable symptoms.
How to tell if a food is low or high FODMAP?
The most valuable and simple tool you can use to navigate the low FODMAP diet is the Monash low FODMAP diet app.
Unfortunately, it is not a free app, but it is the most comprehensive database on FODMAPs available to the general public.
It uses a traffic light system to rank foods as high, moderate and low FODMAP based on different portion sizes.
So not only do you get to know what foods are generally high versus low FODMAP but exactly what portions you should be eating to carry out the elimination phase successfully.
There are also a tonne of low FODMAP recipes on this app that you can use.
If the elimination phase is not done correctly from the get go, it can really drag out the process.
Stage 1: The elimination phase
The elimination phase should be done for 2-6 weeks.
There are a couple of ways you could go about it.
The most simple and quickest way is to jump right in. In this case I suggest becoming familiar with the low FODMAP foods in the Monash app and writing yourself a weekly meal plan with low FODMAP recipes for breakfast, lunch and dinner & suitable snack options.
Like any diet, preparation is key. You will have the most success when you have put some forethought into what you are going to eat for the week ahead.
You can do it on the fly but it is much harder to achieve.
I would also avoid eating out during this time. It is going to be very difficult to find options that are completely low FODMAP in cafes and restaurants.
Once you have finished the low FODMAP diet process in full. You can be more specific about avoiding your individual triggers. But during the elimination process, try to eat at home.
Another way to achieve a low FODMAP diet is to systematically change each meal throughout the day to a low FODMAP option.
If you find overhauling your diet to be quite an overwhelming task, tackling it meal by meal every few days can be a great option.
Start at breakfast and work your way through until you are comfortably following a low FODMAP diet.
It may take longer, but for some people, the time and energy burden is a lot lower doing it this way.
Stage 2: The reintroduction phase
The reintroduction phase is a bit like being a detective.
The goal of this phase is to regain your food freedom and identify your trigger foods. This should only be done once your symptoms have settled.
The FODMAP challenge and reintroduction phase is a series of food challenges that help you test your tolerance levels to each FODMAP group.
One FODMAP group is challenged per week and is tested for 2-3 days during that week.
If you do not react to a FODMAP group you can reintroduce these foods in small amounts as you feel comfortable. If you strongly react to a FODMAP group then these foods will remain out of your diet to keep your symptoms settled in the long run.
It is important to use specific foods when testing as foods that are high in two or more FODMAPs may skew results when testing. Maintaining a base low FODMAP diet is also important for the same reason.
You don’t want to skew results when testing.
The washout periods between tests are also crucial, especially if you have reacted to a food. You will need to wait until your symptoms settle before testing again.
Below is an example of a reintroduction/testing schedule.
Fructans and galactans pass through the digestive system more slowly and therefore take longer to trigger a reaction. So you may wish to have a normal low FODMAP day between challenges.
Monday – small FODMAP quantity
Tuesday – normal low FODMAP day
Wednesday – medium FODMAP quantity
Thursday – normal low FODMAP day
Friday – Large FODMAP quantity
Saturday & Sunday – 2-3 day washout period
In regard to appropriate testing foods, you could refer to the infographic below from our team at Ideal Nutrition.
There is no right or wrong time to test. Do what suits you. If you’re anxious about symptoms returning such as having loose bowel movements, do it in the evening when your home.
During this process take note of your challenges and if there were symptoms and if so, what were they and how severe were they.
The point of this process is to get a better understanding of your individual triggers and tolerances, so the more detailed notes you take during this time, the more data you will have available to use when creating a personalised diet for symptom management.
Challenges and reactions could also be noted in the Monash low FODMAP app.
Stage 3: Personalising your low-FODMAP diet
This part of the diet is often not explained online, however is definitely an important step. There are so many ways to go about personalising your diet and a lot of it will still be trial and error.
The challenges will give you a good idea of what FODMAP groups you react to and which ones you don’t. But how do you apply this knowledge to your diet as a whole?
There are some decent resources online that list high FODMAP food by the FODMAP which they are high in but not many are an exhaustive list.
Again, the Monash app is perfect for this part of the process. You can actually go in and adjust your settings based on your reactions to the challenges.
In other words, the traffic light system to be completely individualised to you.
Using the app in this way for a few months can help you to get a good grasp on the food you can reintroduce into your diet and which foods you should continue to avoid to prevent symptoms from occurring.
Why the low FODMAP diet is not a long term solution
The low FODMAP diet is not designed to be a forever solution. The reintroduction and personalisation aspects of this process are an absolute must!
The first reason for this is that the diet is very restrictive and you will likely have a hard time meeting your nutrient requirements long-term.
A diet this restrictive is also likely to contribute to a general lack of variety in the diet. Diet variety is very important for the health and diversity of the gut microbiome.
The gut microbiome is the term used to describe the trillions of microbes which live in our digestive tract.
The low FODMAP diet also limits prebiotic fibers which can also be detrimental to the gut microbiome.
It is important to reintroduce the FODMAPs back into your diet sooner rather than later to help decrease the chances of making your food intolerances worse.
Top low FODMAP resources
- The Monash app – https://www.monashfodmap.com/ibs-central/i-have-ibs/get-the-app/
- Monash low FODMAP recipes – https://www.monashfodmap.com/recipe/
- Monash low FODMAP blog – https://www.monashfodmap.com/blog/
- Healthy Food Guide recipes – https://www.healthyfood.com/health-information/healthy-low-fodmap-recipes/
- FODMAP everyday resources list – https://www.fodmapeveryday.com/resources/downloadable-resources-tools/
The low FODMAP diet can be a great solution for the management of IBS. However, always speak to a doctor first in order to rule out any other reasons for your symptoms.
Something I will add to wrap things up is that I have never actually seen somebody implement the Low FODMAP diet well without the guidance of a dietitian.
Aidan Muir is an Accredited Practising Dietitian and Sports Dietitian specialising in fat loss, muscle gain and performance. Aidan runs the Ideal Nutrition service in Brisbane, Australia.