A consensus document on role of exclusion diets in IBS has been developed to help facilitate dietary counselling in daily practice.
The consensus is based on the opinions of Spanish experts from various national scientific societies with the aim of establishing recommendations applicable to the care of IBS patients. The paper seeks to clarify concepts and improve the management of IBS patients by applying objective criteria for the exclusion of lactose, gluten or FODMAPs from the diet.
FODMAP Exclusion in IBS
There are currently two established dietary interventions in the management of IBS. The first-line advice is based on a regular meal pattern along with restriction of a range of different foods including alcohol, caffeine, spicy foods, fat and gas-producing food. The second-line dietary advice consists of a FODMAP-restricted diet, which comprises two phases. Whilst a top-down approach is more commonly employed, it may also be managed the other way around (the bottom up approach), which involves only restricting high-FODMAP foods with further withdrawal of lower-FODMAP foods until tolerance is achieved.
Using the top-down approach involves complete FODMAP exclusion over the first 4-8 weeks until symptom remission is achieved. Reintroduction of high-FODMAP foods then takes place until individual tolerance is reached. This approach is usually recommended for patients who do not usually ingest high quantities of FODMAPs, are intensely symptomatic or prefer this approach.
Using the bottom-up approach, the exclusion of FODMAPs is partial and is focused around the higher-FODMAP foods. This also lasts for 4-8 weeks until tolerance is achieved and is usually recommended for patients who consumer high amounts of FODMAPs, are moderately symptomatic or prefer this approach.
A FODMAP-restricted diet is recommended for patients with IBS-D or IBS-M who do not respond to the first-line dietary treatment.
Lactose Exclusion in IBS
It is useful to consider the potential incidence of lactose intolerance in people with IBS. A recent study demonstrated that patients with IBS do not have higher levels of lactose malabsorption compared with the general population, however, they do have higher levels of intolerance as they are particularly hypersensitive. In those with IBS, the symptoms are more severe and, more importantly, ‘worse lived’ when compared to the general population.
The consensus paper states there is evidence to support lactose exclusion as a potentially effective dietary treatment in IBS and should be recommended when symptoms are identified in association with the ingestion of dairy products or evidence of lactose malabsorption is present. Exclusion may be partial with monitoring of patient response and an increasing level of restriction implemented accordingly. However, the expert consensus was that it was advisable for complete exclusion to be implemented initially and then subjected to monitoring. Whilst the duration of exclusion cannot be predetermined, response to exclusion may be assessed after 4-8 weeks. Reintroduction of a normal diet on a gradual, step-by-step basis, whilst ensuring tolerance, can then be undertaken.
Gluten Exclusion in IBS
In patients with IBS who experience symptom improvement on a gluten-free diet (GFD), gluten-related disorders including coeliac disease (CD), wheat allergy (WA) and non-coeliac gluten sensitivity (NCGS) must be ruled out. The consensus paper states that IBS and NCGS are not synonyms and whilst some patients initially diagnosed with IBS may improve with a GFD, only a certain number will do so because of gluten itself and therefore have NCGS. There are currently no markers to identify this subgroup of patients who will experience improvement and it is important to be aware that response to a GFD may occur later than seen in the studies. The evidence to support universal gluten exclusion for all patients with IBS is low (RCTs with limited quality). If gluten exclusion is recommended it should be complete as this was used in the research to date. In patients with IBS, without evidence of gluten-related disorders, exclusion should only be considered in the setting of a low FODMAP diet. Exclusion durations should be at least 8 weeks in order to assess efficacy, although in most individuals improvements are observed within a week. In the absence of improvement, NCGS diagnosis should be considered uncertain. Response to the reintroduction of a normal diet should be regularly assessed in the form of a masked, double-blind approach to avoid a nocebo effect.
The paper also considers the nutritional consequences or impact of lactose, gluten and FODMAP exclusion in adult patients as well as the importance of patient education in the management of IBS. It concludes by stating that the therapeutic approach to patients with IBS must be an integral one comprising all available measures including education, as well as multidisciplinary working amongst healthcare professionals, to optimise symptom control and improve patient quality of life.