Why should I reintroduce FODMAPs?

Why should I Reintroduce FODMAPs

The low FODMAP diet has been a revelation in helping people to reduce and control symptoms of IBS, and it’s not surprising that many are hesitant to reintroduce high FODMAP foods once they are feeling better. Indeed with the increasing public awareness of the low FODMAP diet it is possible many people are self-treating and have little understanding of the more complex reintroduction phase without guidance from an experienced dietitian.

It is important to understand that the low FODMAP diet is actually a 3 phase diet and the low FODMAP part is just the first phase known as ‘FODMAP Restriction’. The restriction of high FODMAP foods is only designed for the short term to help you determine if you have an intolerance to FODMAPs. However to truly understand your intolerance then tolerance levels must be determined through the structured reintroduction phase. This is the second phase of the entire low FODMAP diet and is a vital part of the diet which should be completed by all of those who follow the diet.

Some people may ask the question ‘Why can’t I stop eating high FODMAP foods forever if my symptoms are so much improved? This article will hopefully answer this question and explain why you should always reintroduce FODMAPs to personal tolerance levels.

The RISKS of NOT Reintroducing FODMAPs

The Risks of NOT Reintroducing

1. Effect on gut microbiota

The first study to assess the impact of the low FODMAP diet on the gut microbiota of people with IBS found that although FODMAP restriction reduced overall IBS symptoms there was also a significant reduction in bifidobacteria after only 4 weeks on a low FODMAP diet. This study by the team at King’s College London is entitled ‘Fermentable Carbohydrate Restriction (FODMAPs) Reduces Luminal Bifidobacteria and Gastrointestinal Symptoms in Patients with Irritable Bowel Syndrome’ and is available here (open access). Another interesting finding in this study was that those people with higher levels of bifidobacteria before they started a low FODMAP diet had a greater reduction in levels of bifidobacteria. Bifidobacteria has proven beneficial effects on health while low levels of this bacteria in combination with other low bacterial diversity is linked to the pathology of disease.

Interestingly previously studies have also demonstrated that some people with IBS already have reduced levels of Bifidobacteria compared to healthy controls. Reduced levels of Bifidobacteria are related to an increase in pain scores reported by people with IBS. Theoretically if this further reduction in Bifidobacteria is maintained by long term restriction of FODMAPs then this has clear health implications.

The Monash University research team also investigated the association between a low FODMAP diet and the changes to your gastrointestinal microbiota. Their paper entitled ‘Diets that differ in their FODMAP content alter the colonic luminal microenvironment’ is available here (requires access). The Monash authors concluded that ‘Diets differing in FODMAP content have marked effects on gut microbiota composition’. This trial showed that a 3 week FODMAP restriction diet was associated with a higher faecal pH and a significant reduction (47%) in colonic bacterial groups that have known health benefits including bifidobacteria.

Whether the low FODMAP diet causes a continued decrease in bifidobacteria or other important gut bacteria in the long term or if this decrease has any negative effects on the health of the gut long term will continue to be studied.  What these initial studies indicate however is that a continued low FODMAP diet is likely to have detrimental effects on your long term gut health. This may mean that although a short term low FODMAP diet helps reduce symptoms initially by continuing to follow a low FODMAP diet it may lead to increased symptoms or possible increased chances of worsening gastrointestinal health in the future.

For a brief summary of the effect on gut microbiota and the importance of reintroducing FODMAPs the following quote provides a nice conclusion on what is currently known and what the experts believe. “Strict FODMAP restriction induces a potentially unfavorable gut microbiota, although the impact of this consequence upon health is unknown. This observation puts additional impetus on the reintroduction of FODMAPs according to tolerance during the maintenance phase of the diet.” Taken from ‘Controversies and Recent Developments of the low FODMAP diet’, please follow the link here for this excellent open access paper.

2. Lack of Prebiotics

One of the main reasons why a reduction in FODMAPs reduces the gut microbiota is most likely because foods high in FODMAPs are also prebiotics.  Prebiotics are natural fermentable food components that result in specific changes in the composition and/or activity of the gut microbiota, and therefore confer benefits upon the host.  As prebiotics are basically digested by your gastrointestinal microbiota they are known as food for the good bacteria in your gut.

Prebiotics include fructo-oligosaccharides (FOS), such as inulin or fructans and galacto-oligosaccharides (GOS) including stachyose and raffinose.  You may recognise these words from following the low FODMAP diet. During the FODMAP Restriction phase of the diet you needed to avoid these prebiotic carbohydrates (fibres) and this means not eating foods such as onions, garlic, leeks, asparagus, beans, pulses, cashews, pistachios, wheat foods and more! Studies have shown that a low FODMAP restriction diet can reduce intakes of prebiotic fructans and GOS by up to 50%.

By not consuming high FODMAP foods which contain these prebiotics you may negatively affect the communities of bacteria living in your gut in the long term which could then impact on your overall health including increasing gastrointestinal symptoms. This is a very important issue and is why the leading research institutes in the world when conducting clinical trails of the low FODMAP diet continue to not only assess the impact of the diet on symptoms but also assess its impact on the gut microbiota.

3. Potential nutritional inadequacy

Following any restricted diet long term can lead to a reduction in the range of nutrients consumed and therefore nutritional inadequacy. There are plenty of foods to consume on a restricted low FODMAP diet so this should not be an issue for most, especially as it is a diet that should only be followed for a limited time. However many people who follow a low FODMAP diet, either short term or long term can end up eating the same foods over and over with little variety in their already restricted diet.

Research has shown that even a short term low FODMAP diet can decrease nutrient intakes. A study in Sweden has shown a reduction in carbohydrates and dietary fibre along with total energy intake during a 4 week low FODMAP diet. Similarly intakes of carbohydrates, starch, total sugars, and calcium were lower after a 4 week low FODMAP diet in the UK with weight loss also seen in those following a low FODMAP diet. A significant decrease in nutritional intake can also cause unintended and for some unwanted weight loss.

It is worth noting that the individuals in these studies had been given advice by an experienced dietitian and yet still some of them did not manage to maintain their nutrient intakes on a low FODMAP diet. All of these patients would however have also completed the reintroduction phase of the low FODMAP diet under guidance from a dietitian where these nutritional deficits would have been corrected by reintroducing FODMAPs.

This evidence highlights the importance of replacing high FODMAP carbohydrate foods e.g. wheat and vegetables with suitable low FODMAP alternatives not only to maintain nutrient intake but to prevent unwanted weight loss. Also ensuring calcium intake is maintained by consuming suitable amounts of low lactose foods e.g. yoghurt and cheese while avoiding high lactose foods e.g. milk and replacing milk with plant based alternative milks e.g. rice or almond milk.

On a separate note but rather interestingly several studies have also shown that a gluten free diet can reduce Bifidobacteria and Lactobacillus and those following a gluten free diet can have lower nutrient intakes of calcium, iron, folate as well as fibre when compared to a gluten containing diet.

The bottom line….Reintroduce FODMAPs for increased chances of having better gastrointestinal health in the long term. There may be unintended consequences that affect your gut microbiota that have not fully been researched yet.

If this has sparked an interest in the gut microbiota you will not find many better explanations and summary of the research than in the video below, presented by Stephen Collins. It gives a really nice overview of IBS and the Gastrointestinal Microbiota. FODMAPs are not mentioned until the last few minutes of the presentation, and then only briefly, but this presentation is really all about the potential for altering the gut microbiota to influence IBS symptoms.

Watch this excellent presentation on the role of the intestinal microbiome in irritable bowel syndrome

One final point on gut microbiota is over recent years several commercial gut microbiome testing facilities have become available. People are very keen it seems to have their gut microbiota tested and then have a treatment to ‘cure’ their symptoms based on these results. This sounds fantastic but in reality there is simply not enough scientific information to make an informed and evidenced based treatment decision. If you are thinking of doing this and have read nothing but positive reports on these testing procedures then to provide some balance to the debate have a read of this short article: Can I Test the Health of My Gut Microbiota?


The BENEFITS of Reintroducing FODMAPs

The Benefits of Reintroducing

1. Quality of life

“As a restrictive diet, the low-FODMAP diet carries risks of nutritional inadequacy and of fostering disordered eating, which has received little attention” (Peta Hill, Jane G. Muir, PhD, and Peter R. Gibson, MD. 2017. Controversies and Recent Developments of the low FODMAP dietPlease follow the link for the excellent open access paper this quote is taken from.

Finding out a person’s individual FODMAP tolerance is as much important for the mind as the body (or gut). Most people find that following the restriction phase of the low FODMAP diet is a challenge, not only because it may cut out some of their favourite foods, but also for many social factors such as cooking for the family, eating out, holidays, as well as the cost implications a ‘free from’ diet can result in. Continuing to follow a restrictive diet long term may start to affect your relationship with friends and family as it prevents you joining in at social food occasions. For example you may become more anxious and concerned about how food is prepared and experience anxiety around unfamiliar foods. Or end up always ‘self-catering’ at social events or even avoid social situations around food and eating altogether.   

As with any lifestyle change, if it is enjoyable and in keeping with normal routine it is more likely to be followed. In a recent study which I led on, it was found that those people with IBS who reintroduced FODMAPs had the same food related quality of life as those who consumed a normal diet and ate whatever they wanted. Sticking to the low FODMAP restriction diet could impair your food related quality of life – meaning you end up enjoying food less due to the self imposed restrictions.

2. A personalised balanced modified FODMAP diet

A balanced diet is completely achievable on the low FODMAP diet, however if you are doing the diet on a long term basis the amount of restrictions can become laborious, especially if cooking for others as well. In the long term this can lead to sticking to patterns of eating which are easier (ie. only jacket potatoes suitable in the staff canteen?) and may lead to a more restricted diet overall. If you are not replacing the high FODMAP foods with suitable substitutes your diet may become nutritional inadequate as mentioned above (see point 3. Potential nutritional inadequacy). A balanced diet is the best diet for overall health, and so having a wider choice of foods available to chose from will help to achieve this more easily.

In fact research evidence so far indicates that the reintroduction of FODMAPs following dietetic advice leads to a modified FODMAP diet which does not impact on nutritional inadequacy. Indeed the previously observed significant reduction in carbohydrate, calcium and fibre intake seen in those following a 4 week low FODMAP restriction diet have increased their fibre, calcium and carbohydrate intake long term through a modified FODMAP diet. Following the reintroduction phase roughly 80% of people manage to personalise their diet by modifying the amount of high FODMAP foods they eat while still maintaining symptom control. The most common foods that needed to be modified included garlic, onion, wheat and dairy products.

3. Your relationship with food

Psychological distress due to food restriction could become an issue with the low FODMAP restriction diet if you do not reintroduce FODMAPs. There are lots of different factors which can impact on IBS symptoms including stress and anxiety, hormones, the gut-brain axis, microbiota dysbiosis and food, but by only focusing on how foods affect you this may lead to blaming all symptoms on what or when you have eaten. As we eat many times per day this can become mentally consuming! If you can reintroduce successfully, it can give confidence that IBS symptoms are managed as well as possible with diet and understanding that some symptoms may never fully disappear due to other factors beyond your control.

There is evidence of increased risk for disordered eating (not an eating disorder) in those with IBS and other gastrointestinal disorders. Gastrointestinal symptoms may create food aversion and cause alterations to eating patterns. Other disordered eating traits can be seen in people who religiously adhere to a restrict dietary programme such as the restriction phase of the low FODMAP diet. On the extreme end of the scale an obsessive focus on only choosing, planning, purchasing and consuming low FODMAP foods with the exaggerated faith that these will ‘cure’ their IBS is likely to impact their physical and psychological well-being.

Sticking to a restricted low FODMAP diet long term may hide something more problematic causing your symptoms. The restriction phase of the low FODMAP diet is effective in 50-80% of patients meaning it will not be effective in 20-50%. Therefore for some patients there is a real possibility that initial improvements in symptoms are a result of a placebo response. Once this placebo response diminishes often someone will continue with a restricted low FODMAP diet but continue to restrict further foods or introduce further ‘diets’ in an attempt to improve their symptoms e.g. Paleo diet, low histamine diet etc. This can lead to an accumulation of dietary restrictions while symptoms continue to get worse. Many patients I meet are doing this and they have their ‘safe’ and ‘unsafe’ foods within their many dietary restrictions. The problem for these individuals is what happens when their ‘safe’ foods then become ‘unsafe’?

Only by reintroducing can you then identify which FODMAPs are significant triggers of your IBS symptoms which will allow you to broaden your diet. There is almost a public confusion that the low FODMAP diet ‘cures’ IBS. Being completely symptom free with IBS is unlikely.  Therefore although it is important to avoid the FODMAP triggers of IBS, the key is to incorporate this into a nutritionally balanced diet for life which for most people seems to be a modified FODMAP diet. This is best shown from long term (average 12 months) dietary studies of the low FODMAP treatment where people have completed the reintroduction phase and are consuming a personalised modified FODMAP diet to their own tolerance levels. Clearly a placebo response cannot continue for 1 year and for the vast majority of people to maintain symptom control of IBS long term the reintroduction of FODMAPs to personal tolerance levels is the most important part of the FODMAP treatment.

4. Your gastrointestinal health

A regular intake of FODMAPs provides your gut with prebiotics that stimulate the growth and/or activity of bacteria in the digestive system which has been shown to be beneficial for health.


The plan ultimately is to find a balance between having enough FODMAPs in the diet to maintain a manageable and enjoyable diet, having a good amount of natural prebiotics whilst managing IBS symptoms. For detailed guidance into reintroducing FODMAPs, you can purchase a paperback copy or Kindle version of the self-hep guide to the reintroduction phase on Amazon.