Dietary triggers such as gluten and highly fermentable oligo-, di- and monosaccharides and polyols (FODMAP)-containing foods have been associated with worsening irritable bowel syndrome (IBS) symptoms. However, the true impact of dietary restriction on IBS symptoms has remained unclear. The aim of this study was to conduct a systematic review and meta-analysis of randomized controlled trials (RCTs) examining the efficacy of exclusion diets (we focused on low FODMAP and gluten-free diets (GFD)) in IBS.
We conducted a search of the literature using the electronic databases MEDLINE (1946 to November 2017), EMBASE (1974 to November 2017), Cochrane Central Register of Controlled Trials (November 2017), and Cochrane Database of Systematic Reviews (2005 to November, 2017) for RCTs of exclusion diets in IBS. Two independent reviewers screened citations and a third reviewer resolved disagreement. Two independent reviewers performed eligibility assessment and data abstraction. For inclusion, RCTs that evaluated an exclusion diet versus an alternative or usual diet and assessed improvement in either global IBS symptoms or abdominal pain were required. Data were synthesized as relative risk of symptoms remaining using a random effects model. Quality of evidence was assessed using GRADE methodology.
A total of 1726 citations were identified. After full-text screening a total of nine studies were eligible for the systematic review. There were two RCTs of a GFD, involving 111 participants. Both selected patients who responded to a GFD and then randomized them to continue the diet or have the diet “spiked” with gluten. A GFD was associated with reduced global symptoms compared with a control diet (RR = 0.42; 95% CI 0.11 to 1.55; I2 = 88%), although this was not statistically significant. There were seven RCTs comparing a low FODMAP diet with various control interventions in 397 participants. A low FODMAP diet was associated with reduced global symptoms compared with control interventions (RR = 0.69; 95% CI 0.54 to 0.88; I2 = 25%). The three RCTS that compared low FODMAP diet with rigorous control diets had the least heterogeneity between studies, but also the least magnitude of effect. The overall quality of the data was “very low” according to GRADE criteria.
There is insufficient evidence to recommend a GFD to reduce IBS symptoms. There is very low quality evidence that a low FODMAP diet is effective in reducing symptoms in IBS patients.
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This work was supported by the American College of Gastroenterology Institute and the Canadian Institute for Health Research. Paul Moayyedi is the Principal Investigator for the Inflammation, microbiome, and alimentation: gastro-intestinal and neuropsychiatric effects (IMAGINE) - a Strategy for Patient Oriented Research (SPOR) chronic disease network that evaluates the role of the microbiome and diet in IBS.
Exclusion Diets in IBS Search Strategy
“Database: Embase <1974 to 2017 November 13>, OVID Medline Epub Ahead of Print, In-Process & Other Non-Indexed Citations, Ovid MEDLINE(R) Daily and Ovid MEDLINE(R) 1946 to Present, EBM Reviews - Cochrane Central Register of Controlled Trials <November 2017>, EBM Reviews - Cochrane Database of Systematic Reviews <2005 to November 12, 2017 Search Strategy:
exp Irritable bowel syndrome/ (28258)
exp Irritable colon/ (28258)
(Irritable bowel syndrome or irritable colon* or IBS).tw,kw. (34832)
1 or 2 or 3 (41261)
exp diet, gluten-free/ (8860)
exp gluten free diet/ (8860)
((gluten* adj2 free) or glutens).tw,kw. (11497)
exp fructose oligosaccharide/ or exp polyol/ or exp fructose/ or exp galactose oligosaccharide/ (242440)
exp diet/ (590580)
(FODMAP or FODMAPs or saccharides or oligosaccharide or disaccharide or monosaccharide).tw,kw. (63021)
exp diet restriction/ (145695)
exp fructan/ (8749)
(polyol or polyols or diet restriction or dructo-oligosaccharides or galacto-oligosaccharides or fructans or fructose or galactans or lactose or sorbitol or mannitol or xylitol or maltitol).tw,kw. (166833)
exp carbohydrate diet/ or exp Dietary Carbohydrates/ (46682)
exp sweetening agent/ (298613)
(diet or diets or dietary or nutrition or food).tw,kw. (1788646)
4 and 18 (6544)
randomized controlled trial.pt. (879623)
controlled clinical trial.pt. (183129)
double-blind*.mp. or blind*.tw. (936966)
clinical trial:.mp. (2709808)
19 and 28 (2844)
remove duplicates from 29 (1998)
((child/ or Pediatrics/ or Adolescent/ or Infant/ or adolescence/ or newborn/) not (adult/ or aged/)) or ((baby or babies or child or children or pediatric* or pediatric* or peadiatric* or infant* or infancy or neonat* or newborn* or new born* or kid or kids or adolescen* or preschool or pre-school or toddler*) not (aged or adult* or elder* or senior or men or women)).ti. (4352199)
((exp animals/ or exp animal/ or exp nonhuman/ or exp animal experiment/ or animal model/ or animal tissue/ or non human/) not (humans/ or human/)) or ((rats or mice or mouse or cats or dogs or animal* or cell lines) not (human* or men or women)).ti. (10857825)
case report/ or case reports/ or (case report or case series).ti. (4192672)
note/ or editorial/ or letter/ or Comment/ or news/ (3898425)
30 not (31 or 32 or 33 or 34) (1725)