IBS is a chronic digestive condition impacting up to 15% of the global population. It is characterised by a range of symptoms.
These symptoms of IBS include:
- Bloating
- Abdominal pain
- Changes in bowel patterns (e.g., constipation or diarrhoea) [Source: Pubmed]
Up to 70% of those with IBS report that food is a trigger for their symptoms, and it’s not uncommon for many sufferers to attempt to restrict known triggers. [Source: Pubmed]
Due to the wide range of foods that have the potential to trigger IBS symptoms, it’s uncommon for a single food to be the culprit. [Source: Pubmed]
Before the development of the low FODMAP diet, the dietary advice was generic and not personalised. This includes suggestions such as:
- Spacing meals
- Reducing fibre
- Eliminating lactose
- Avoiding trigger foods (commonly wheat, dairy, fructose, caffeine, and alcohol)
Suggestions such as the removal of lactose-containing foods remain controversial as all those with IBS may not be sensitive to this. [Source: Pubmed]
A low FODMAP diet is a dietary tool that restricts a range of carbohydrates found in common foods. Due to changes in the digestive system, foods high in FODMAPs may trigger or worsen digestive symptoms.
Rather than these foods being the cause of IBS, they may simply place extra pressure on the gut when there is already an imbalance. These imbalances are often referred to as the root causes, and in IBS, they include:
- Motility changes
- Visceral hypersensitivity (increased sensitivity of the nerves in the gut)
- Low-grade inflammation (which can follow food poisoning or a viral infection)
- Altered microbiota (imbalances in the gut bacteria)
The low FODMAP diet has been devised to remove certain food that contains short-chain carbohydrates. These carbohydrates are poorly absorbed and easily fermented by the bacteria in the gut (the gut microbiome). [Source: Pubmed]
This fermentation process may then lead to increased water entering the gut as well as an increase in gas production.
This ultimately leads to abdominal distention (visible bloating) and IBS symptoms such as pain and altered bowel movements. [Source: Pubmed]
These changes can lead to symptoms of IBS via effects on the following:
- gut microbiota
- gut barrier
- immune response
- and visceral sensation [Source: Pubmed]
A low FODMAP diet is a method of reducing the amount of fermentation taking place in the gut.
This can often help reduce the severity of IBS symptoms. However, as will be discussed, this is not a long-term diet to follow.
What are FODMAP foods?
FODMAPs are found in a wide range of seemingly unrelated foods. These include:
Fruits:
High FODMAP fruits include apples, pears, mangoes, cherries, and dried fruit.
Vegetables:
High FODMAP vegetables include garlic, onion, cauliflower, leeks, and mushrooms
Grains and cereals:
High FODMAP grains and cereals include wheat and rye.
Legumes:
High FODMAP legumes include beans, lentils, and chickpeas
High lactose dairy:
High lactose dairy foods include soft cheeses and milk
High lactose nuts:
High lactose nuts include pistachios and cashews
Sugars and Sweeteners:
FODMAPs can also be found in common sugar-sweetened foods and drinks. These are often in the form of fructose and sugar polyols (sorbitol, xylitol, erythritol) [Source: Monash]
How do I follow a low FODMAP diet?
Even though the list of FODMAP-containing foods is long, it’s uncommon for all of these foods to be an issue.
However, to identify specific triggers, the diet begins with an elimination phase with 2 further phases following this.
| Name | Purpose | Duration |
| Phase 1 Elimination Phase | The strictest phase of the diet to remove all potential FODMAP culprits. | 2-6 weeks |
| Phase 2 Reintroduction Phase | The previously restricted foods are reintroduced in a specific order to assess for triggers. | 4-8 weeks |
| Phase 3 Personlisation | Often seen as a long-term strategy where the offending foods are avoided. | Discussed below |
What can I eat on a low FODMAP diet?
A wide range of foods are permitted during the elimination phase of the low FODMAP diet.
These include:
Fruits:
Low FODMAP fruits include kiwi, strawberry, lime, lemon, raspberry, and pineapple
Vegetables:
Low FODMAP vegetables include rocket, bean sprouts, bok choy, tomato, turnips, and carrots
Grains and cereals:
Low FODMAP grains and cereals include oats, buckwheat, and rice
Low lactose dairy:
Low lactose dairy foods include hard cheeses such as cheddar, camembert, and brie
How long is low FODMAP for?
When used in isolation, phase 3 of the low FODMAP diet is considered a long-term approach.
In simplest terms, this involved identifying the specific foods that trigger symptoms and avoiding them forever.
The problem that some have with this approach is that it does not address the reason why the reaction may be taking place. For example, you may be reacting to garlic, but why is this reaction taking place?
With this in mind, if FODMAP triggers are identified, their removal is primarily for symptom management and not a treatment.
This focus on food being the cause of symptoms (rather than aggravating an underlying issue) can lead to people becoming hyper-focused on their diet. This had led some to comment that a low FODMAP diet should not be considered in those with current or historical eating disorders. [Source: Pubmed]
The reduction in fermentation also impacts the growth of beneficial bacteria in the gut. Research indicates that key, friendly bacteria such as Bifidobacterium and Faecalibacterium prausnitzii are reduced in number in those on a low FODMAP diet. [Source: Pubmed]
Due to these potentially negative aspects of the low FODMAP diet, it is not considered a long-term approach.
[Source: Pubmed]It’s not all about FODMAPs
Even when adopting a low FODMAP approach, working to address the underlying reason for IBS symptoms is an essential part of the approach.
By addressing these underlying issues or imbalances, the aim is to reintroduce the FODMAP foods that we were triggering symptoms.
Several approaches have been shown to have a similar or increased level of benefit to a low FODMAP diet.
These have shown to be beneficial even without restricting FODMAP-containing foods.
- Probiotic supplementation [Source: Pubmed]
- Prebiotic supplementation [Source: Pubmed]
- Yoga and meditation [Source: Pubmed]
- Gut directed hypnotherapy [Source: Pubmed]
With the overlapping causing of digestive symptoms, an approach than combines these factors may be most effective.
Summary
While a low FODMAP diet can be helpful in reducing symptoms of IBS, it doesn’t address the underlying imbalance.
Rather than asking ‘what food is causing symptoms?’ we ask ‘why is the body reacting to food in that way?’
By addressing this underlying issue, the aim is to move towards an unrestricted diet while remaining symptom-free.
