Low FODMAP Diet: Evidence, Doubts, and Hopes

Abstract

Food is often considered to be a precipitating factor of irritable bowel syndrome (IBS) symptoms. In recent years, there has been a growing interest in FODMAPs (Fermentable Oligo-, Di-, Mono-saccharides, And Polyols), which can be found in many common foods. A low FODMAP diet (LFD) is increasingly suggested for IBS treatment. However, long-term, large, randomized controlled studies are still lacking, and certainties and doubts regarding LFDs have grown, often in a disorderly and confused manner. Some potential LFD limitations and concerns have been raised, including nutritional adequacy, cost, and difficulty in teaching the diet and maintaining it. Most of these limitations can be solved with the involvement of a skilled nutritionist, who can clearly explain the different phases of the LFD and ensure nutritional adequacy and compliance. Further studies should focus on new methods of teaching and learning the LFD and on predictors of response. Moreover, particular interest should be focused on the possible use of LFD in gastrointestinal diseases other than functional disorders and, possibly, also in non-gastrointestinal diseases. The aim of the present review was to clarify the effective and appropriate indications and limitations of an LFD and to discuss its possible future uses.

A Low-FODMAP Diet for Irritable Bowel Syndrome: Some Answers to the Doubts from a Long-Term Follow-Up

“…In recent years, the LFD has gained increasing popularity among gastroenterologists and patients. Even if it cannot be considered a panacea for all patients affected with GI disturbances, there are now several studies proving its efficacy [8]. Indeed, a recent systematic review provided evidence that an LFD is effective in improving IBS symptoms [12].…”

“…However, it is not clear whether the patients are really able to precisely recognize the foods which trigger their symptoms or if they simply think they are intolerant to some foods, often depicted as dangerous by the media, relatives and friends, e.g., gluten and/or lactose. A relatively new approach to IBS therapy is the restriction of short-chain fermentable oligosaccharides, disaccharides, monosaccharides and polyols (FODMAP), the so-called low-FODMAP diet (LFD) [8].…”

“…The "FODMAP" term was coined by the Monash group and presented to the scientific community in a paper concerning a hypothesis (the FODMAP hypothesis) about the pathogenesis of Crohn's disease [9]. Since then, an LFD has been suggested for many GI disorders, mainly IBS, and also for non-GI disease [8].…”

“…As it is an exclusion diet, the critics of the LFD pose doubts regarding its nutritional adequacy and its complexity and efficacy, mainly linked to a supposed poor compliance in the long term [10]. An important issue is the role of FODMAPs as prebiotics: especially through metabolization of FOS (fructooligosaccharides) and GOS (galactooligosaccharides), they favor the growth of beneficial bacteria and increase the production of SCFA, which have an important protective and trophic activity on the colonocytes [8]. A FODMAP reduction, potentially inducing a decrease of fiber intake, could increase the risk of constipation and induce possible changes of the intestinal microbiota with a decrease in the production of SCFA.…”

Effects of Low and High FODMAP Diets on Human Gastrointestinal Microbiota Composition in Adults with Intestinal Diseases: A Systematic Review

“…It is not known whether the impact of the low FODMAP diet on the gut microbiota is long-term, as longitudinal follow-up is only seldomly included in current studies. In addition, most of the studies only report microbiota changes at the end of a restrictive period (4-8 weeks) but do not consider the suggested reintroduction phase, in which fermentable carbohydrate restriction becomes less stringent [78]. With the exception of Harvie et al [25], who found persistent symptom improvement in IBS patients with the reintroduction of FODMAPs, yet did not observe any microbial changes upon the FODMAP diet or 3 months thereafter (possibly due to a loss of samples after a technical issue), the long-term impact of a low FODMAP diet is currently unassessed.…”