Research on the reintroduction phase of the low FODMAP diet

With the low FODMAP diet still being relatively new, there is limited research on the different stages of the diet. There is a lot of research on the first stage which is the ‘low FODMAP elimination diet’. However the most limited research is on stage 2 ‘the reintroduction phase’ and stage 3 ‘a modified low FODMAP diet’ (which is a modified version of the low FODMAP diet including high FODMAP foods to personal tolerance). By the way if you hadn’t realised there are actually 3 stages to the low FODMAP diet then please read the article linked below.

Following the low FODMAP diet long term…What is a modified low FODMAP diet?


Research on Reintroducing FODMAPs

Currently in press:

Long term effectiveness of short chain fermentable carbohydrate (FODMAP) restriction in patients with irritable bowel syndrome

When I worked at King’s College London I was fortunate enough to lead on the first ever long term study in the UK looking at the reintroduction phase of the low FODMAP diet. I found that the vast majority of people, after completing the low FODMAP elimination diet, continued to follow a modified version of the low FODMAP diet after reintroducing FODMAPs. Importantly 71% of these people continued to have relief of their IBS symptoms after completing the reintroduction phase and had excellent food related quality of life measures. This is the first evidence to show that you do not need to continue to follow the low FODMAP elimination diet to provide effective IBS symptom relief and you can include high FODMAP foods (after completing the reintroduction phase) without this affecting your IBS symptoms. Some other important questions this research helped to answer included:

1. Do people reintroduce FODMAPs after starting a low FODMAP diet?

YES! In fact 97 out of 103 people completed the reintroduction phase.

2. What sort of diet do people follow in the long term after completing the low FODMAP restriction diet and the reintroduction phase?

Out of the 103 participants when followed up one year later:
78 of them continued to follow an adapted low FODMAP diet. Meaning they had reintroduced FODMAPs to their own tolerance levels.
19 followed a normal diet. Meaning they had reintroduced FODMAPs and no longer followed any FODMAP restrictions.
6 continued to follow a low FODMAP restriction diet in the long term (a year later).

Therefore the vast majority of people do reintroduce FODMAPs but continue to follow a modified low FODMAP diet as their normal diet.

3. After you have reintroduced FODMAPs do you still have relief of your IBS symptoms in the long term?

YES! There are two statistical points here. First of all 61% of people found relief of their IBS after following a low FODMAP restriction diet. This is similar to other studies looking at the effectiveness of the restriction phase of the low FODMAP diet. Importantly in those 61% of people 70% of them continued to have relief of their symptoms a year later.

This shows that in the vast majority of people who find the low FODMAP restriction diet effective, even once they have reintroduced FODMAPs they still have relief of their IBS symptoms in the long term.


I presented the study at the Digestive Diseases Federation (DDF) research conference in July 2015. The full paper has not been published but you can access the abstract here.

April 2016:

Follow-up of patients with functional bowel symptoms treated with a low FODMAP diet (open access)

You can access this paper here and the research team at Monash University have also provided a brief critique and overview of the study here.

This study included one hundred and eighty patients who had attended outpatient clinics for low FODMAP dietary advice. 131 (73%) had IBS and 49 (27%) had IBD (inflammatory bowel disease) with IBS symptoms. After finishing the low FODMAP diet and reintroduction the patients were sent questionnaires, on average 16 months later, to obtain information on symptoms and other outcomes.  So what were the results 16 months later?

In the long term (~16 months) the greatest reduction in symptoms were seen in bloating (82%) and abdominal pain (71%).  The vast majority of patients (84%) consumed a modified low FODMAP diet where some foods high in FODMAPs were reintroduced. While 16% continued to follow the low FODMAP elimination diet with all restrictions. Wheat, dairy products, and onions were the foods most often not reintroduced by patients. The interesting and important point here, as I found in the study I completed at King’s College London, is despite reintroducing FODMAPs the majority of patients still reported satisfaction with the modified low FODMAP diet and had control of their symptoms.

This is an important study as it is the largest study to look at the efficacy of the low FODMAP diet in the long term (16 months after initial treatment). It provides evidence that for long term self management of IBS symptoms the reintroduction of FODMAPs leading to a modified low FODMAP diet is an effective treatment and highlights the importance of the reintroduction phase in achieving this. The lack of validated resources to measure the outcomes will make it difficult to compare the results obtained to other research using validated measures.

As new research is completed and published, this post will be updated with the most recent evidence.

Due to the lack of research on the reintroduction stage it means as dietitians we have to use the research literature available combined with our knowledge of elimination diets (such as the low FODMAP diet) and IBS symptom management to help create an effective FODMAP reintroduction plan. The low FODMAP training courses provided by King’s College London which pioneered training to dietitians on all 3 of these stages and is also an essential training course for dietitians involved in the management of IBS.

If you are unable to see a dietitian to help you with the reintroduction phase of the low FODMAP diet you can still make you get the necessary information and support to give you the best chance of successfully reintroducing FODMAPs. There is more research being completed on this important phase which is often available on ‘open access’ along with some really useful articles freely available on the internet. The Re-challenging & Reintroducing FODMAPs book I recently published brings all the current evidence and best practice together into a self help guide to provide extra help for those completing the reintroduction phase whether they have dietetic support or not.