Diets for functional gut symptoms: Benefits must outweigh risks

I know first-hand the challenges that diets present and how hard it is to balance these issues

In an ideal world, everyone with functional gut symptoms that can be modified by diet would benefit from seeing a dietitian experienced in gut health before embarking on a diet of some sort. However, this is not possible given the limited number of resources – both money and personnel. So, in general practice, you will be faced with deciding what dietary recommendations to suggest or, if the patient has already made dietary changes, ensuring nutritional adequacy of their diet.

We cannot ignore the consequences of dietary changes: social implications, anxiety, increased costs, the ability to trigger disordered eating in vulnerable individuals, potential nutritional deficiencies and changes to the gut microbiome. The benefits of any dietary changes need to outweigh these risks, otherwise the diet may have fixed one issue but created others.

As a dietitian with 30 years’ work experience, having also lived with coeliac disease for over 30 years, and cooked for a family member with irritable bowel syndrome (IBS) and a child with allergies and food sensitivities, I know first-hand the challenges that diets present and how hard it is to balance these issues.

Ideally, before any patient embarks on any dietary journey, clinical work-up is recommended. If there are no clinical indicators, a food and symptom diary can sometimes help identify food triggers.

Understanding what is causing the patient’s gut symptoms will help determine the appropriate dietary approach. Targeting the symptoms rather than the cause can mean that dietary changes may not help, thereby making the patient resistant to further changes.

As a clinician, I try to focus on what minimal changes can be made to achieve maximal benefits. I also consider the frequency and severity of the symptoms. Some other factors to consider are the age of the patient, their lifestyle and ability to change their diet.

Whatever you do, don’t rush to prescribe gluten-free, dairy-free or low-FODMAP diets. These diets exclude food groups and can therefore cause nutritional deficiencies and changes to the microbiome. Further, they are not easy to implement or maintain long term.

Gluten-free diets have been frequently used for functional gut issues. However, a recent review study of 1312 adults without coeliac disease showed that of those who responded positively to a gluten-free diet, upon placebo-controlled gluten challenge, only 16 per cent had gluten sensitivity, and 40 per cent had a nocebo response.¹

What this shows is that eliminating gluten is not often effective or required for reducing functional gut symptoms. Even if gluten-containing foods have been identified as a trigger, a low-wheat diet may be a better option as a starting point.² This diet would be less restrictive and less expensive.

Dairy-free diets are also hugely popular among those with functional bowel issues. However, only 8 per cent of New Zealanders have lactose intolerance,³ and dairy allergies are rare in the adult population.⁴

What is interesting is a study by Milan and colleagues that shows some females can be tolerant of lactose but reactive to whole milk.⁵ This means that only a few people with functional bowel symptoms would benefit from a dairy-free diet. If dairy is suspected as a trigger of symptoms, recommending a low-lactose diet would be preferable to a dairy-free diet. Once again, it is a less restrictive diet.

Diets low in FODMAPs (fermentable oligosaccharides, disaccharides, monosaccharides and polyols) are gaining popularity for functional gut symptoms. While these diets are often successful in reducing symptoms, they can be limiting.⁶

Not everyone with functional gut symptoms needs to be on a low-FODMAP diet. Neither would I encourage anyone to trial this diet without dietitian support. Too often, I see patients doing this diet incorrectly and therefore not getting the benefits, while others eat only a handful of foods and end up risking malnutrition.

The goal for functional gut diets should be the improvement of symptoms. While most patients would like to see their symptoms eliminated, this is not likely due to the multifactorial nature of their symptoms.

If a diet is to be trialled, it should only be for four to six weeks before assessing its effectiveness. If it appears to have helped reduce symptoms, then it is important to undertake a re-challenge process to help confirm this. This is the gold standard of any elimination diet.

Choosing the right foods or ingredients in the re-challenge process is critical, otherwise the wrong conclusions can be made. Often, when people re-challenge gluten, they trial wheat in some concentrated form such as bread. The problem with this is that concentrated forms of wheat are high in FODMAPs. A reaction to this food does not necessarily indicate they are reacting to gluten.

We have probably all come across patients who have chosen to change their diet without appropriate professional support. In my clinical practice, I see clients who have been on very restrictive diets for years, yet they have not resolved their gut symptoms sufficiently. Often, these diets are not nutritionally adequate, and patients frequently report they are becoming sensitised to more foods, which may be the result of a worsening of their gut microbiome. If the patient has never tried a food challenge, encouraging them to do this can help confirm their diagnosis and may help liberalise their diet.

It has often been thought that functional gut symptoms do not exist in children, but a study by Brown and colleagues has shown this is incorrect.⁷ However, diets to manage functional gut issues in children, teenagers and young people should be used with extreme caution.

I have noticed that even in preschools, primary and secondary schools, so many children seem to be on gluten and dairy-free diets. Sadly, this is often implemented by parents without consultation with an appropriate health professional. Many issues can arise in these individuals if diets aren’t well managed – growth can be impaired, fussy eating established and even eating disorders triggered.

Diet recommendations should be based on a comprehensive work-up, supported by appropriate dietary advice. Advice needs to be more than the exclusion of foods; it must focus on ensuring a re-challenge phase and be nutritionally balanced in the long term.

Dietitians specialising in gastrointestinal health can help determine which dietary approach is best for the individual and ensure such diets are followed safely in terms of nutritional quality and length of time,so the benefits of the diet outweigh any ongoing nutritional risk.

Julie Leeper is a registered dietitian at Dietary Specialists private practice in Christchurch