Table 1.

Summary of trials reporting on the assessment of the low FODMAP diet compared with other interventions in the management of IBS.

Author, year, country	Study design	Population, diagnostic criteria, and source of recruitment	Intervention and duration	Gastrointestinal symptom and microbial measures	Effect on symptoms	Practice implications
LFD vs. other dietary interventions
Bohn et al. (12) 2015 Sweden	Randomized, multi-center, single blind	n = 67 Adults aged 18–70 years Rome III IBS outpatient clinics	4-week LFD or NICE guidelines (regular meals, reduced fat, fiber, caffeine, and gas reducing foods)	IBS-SSS Bristol stool form scale	Symptoms reduced within both groups (p = <0.00001) but no difference between groups (p =0.2) Mean stool frequency improved significantly within the LFD from baseline to 4 weeks (1.9 ± 0.8) to (1.5 ± 0.7), p = <0.001) as per the Bristol stool form scale. Stool frequency had a non-significant change in the NICE group at baseline) (1.6 ± 0.7) compared to 4 weeks (1.5 ± 0.6), p =0.15). There was a non-significant difference between the groups at 4 weeks (p =0.64)	Overlap between two diet interventions on reduction in ‘gas-forming foods’ and other components of FODMAPs suggest efficacy favoring LFD† Potential for ‘sensible’ eating guidelines to have additive effects to LFD
Eswaran et al. (13) 2016 United States of America	Randomized, single center open label trial	n = 92 Adults aged 18 years and over Rome III (IBS-D subtype) Gastroenterology and primary care clinics	4-week LFD or modified NICE (mNICE) guidelines	11-point likert scale Weekly global symptom assessment Bristol stool form scale	52% LFD vs. 41% mNICE reported adequate relief (p = 0.031) LFD had higher proportion of abdominal pain responders compared with mNICE (51% vs. 23%, p = 0.008) At 4 weeks, stool consistency improved significantly on the LFD compared to the mNICE guidelines (p<0.0001) as per the Bristol stool form scale	LFD† produced a greater improvement in abdominal pain, bloating, stool consistency, stool frequency and urgency at 1-week mNICE guidelines showed no significant improvement in abdominal pain, bloating or stool frequency in any wk Compared to baseline, both diets showed improvement for abdominal pain, bloating, stool consistency, stool frequency and urgency at 4-week
McIntosh et al. (14) 2017 Canada	Prospective, randomized, single blind parallel study	n = 37 Adults aged 18 years and over Rome III Outpatient clinics	3-week LFD or HFD	IBS-SSS 16s RNA profiling	IBS-SSS reduced in LFD but not in HFD (p = <0.001) No differences in α or β diversity between samples from before or after HFD or LFD across IBS subgroups	LFD† showed greater reduction in abdominal symptoms at 3-week HFD led to increased pain at 3 weeks Subgroup analysis showed IBS-M and IBS-D participants had higher bacterial richness after the LFD at 3 weeks
Paduano et al. (15) 2019 Italy	Non-randomized cross over clinical trial	n = 92 Adults aged 18–45 years Rome IV GI outpatient clinics	4-week LFD or gluten-free or Mediterranean diet	IBS-SSS VAS for bloating and abdominal pain Bristol stool form scale	All 3 diets reduced symptom severity (<0.01), bloating (p<0.01) and abdominal pain (p<0.01) The LFD improved stool solidarity from a type 6 to a type 4 (p = 0.03) which was further supported by 79% of LFD participants showing a trend to reach type 4 after 4 weeks on the LFD. No statistically significant differences were observed in stool solidarity for the gluten-free and Mediterranean diets at 4 weeks (data not shown)	Adequate FODMAP distribution over the day was key to preventing overload of FODMAPs in a single meal and inducing symptoms LFD† showed superiority for improving overall & individual GI symptoms, including stool consistency
Staudacher et al. (8) 2011 United Kingdom	Non-randomized clinical control trial	n = 82 Adults aged 18 years and over NICE criteria Dietetic outpatient clinic follow-ups	36-week LFD or standard dietary advice based on NICE guidelines (if a dietitian had already been seen)	16-point VAS scale that included symptoms 7-point Likert scale for symptoms based on IBS global improvement scale	LFD reported greater satisfaction in symptom response (p = 0.38) LFD showed better overall symptom response (p = 0.001), improvement in bloating (p = 0.002), abdominal pain (p = 0.023) and flatulence (p = 0.001)
Zahedi et al. (16) 2018 Iran	Randomized, controlled single blind trial	n = 110 Adults aged 20–60 years Rome III (IBS-D) Hospital GI clinic	6-week LFD or British Dietetic Association guidelines	IBS-SSS Bristol stool form scale	LFD decreased IBS-SSS for abdominal pain intensity (p = 0.001) and frequency (0.017), abdominal distention (p = <0.001), dissatisfaction with intestinal transit (p = 0.001) and interference with daily life (p = 0.005) Mean stool consistency significantly improved in the LFD from baseline to week 6 (5.92 ± 0.45 to 4.3 ± 0.5, p = <0.001) and for the generalized dietary advice group from baseline (5.67 ± 0.61) to week 6 (4.61 ± 0.69, p = <0.001) Mean stool frequency significantly improved in the LFD from baseline to week 6 (3.29 ± 0.87 to 1.91 ± 0.56, p = <0.001) and for the generalized dietary advice group from baseline (3.3 ± 0.77) to week 6 (2.6 ± 0.96, p = <0.001)	Both diets reduced symptom severity LFD compared to generalized dietary advice decreased symptoms for each subset of IBS-SSS and produced relief of symptoms at each timepoint (baseline, 3 weeks, and 6 weeks) Both diets improved stool frequency and consistency at 6 weeks
Staudacher et al. (17) 2017 United Kingdom	Randomized, Double-blind 2x2 factorial design	n = 104 Adults aged 18–65 years Rome III Tertiary hospitals	4-week LFD or sham diet and placebo or multi-strain probiotic formulation	Gastrointestinal symptom rating system (GSRS) IBS-SSS Bristol stool form scale qPCR and 16sRNA sequencing	A higher proportion of patients on LFD had adequate symptom relief than sham diet (p = 0.042) LFD showed lower IBS-SSS score than sham diet (p = 0.01 but not different between probiotic and placebo (p = 0.721) LFD showed a higher proportion of participants achieved clinically meaningful reduction of >50-point reduction in total IBS-SSS compared to sham diet (73% vs. 42%) There was a significant difference in mean stool consistency at 4 weeks between the sham diet (4.3 ± 1.1) compared to the LFD (3.9 ± 1.0), p = 0.008 as per the Bristol stool form scale. The was no significant difference for the placebo and probiotic group for stool consistency (4.2 ± 1.0 vs. 4.0 ± 1.1), p = 0.544, respectively At 4 weeks here was lower absolute Bifidobacterium species abundance in LFD compared to sham diet (8.8 16s rRNA genes/g (SD 0.6) vs. 9.2rRNA genes/g (SD 1.0) mean difference -0.39 rRNA genes/g (95% CI, -0.64 to -0.13, p = 0.008) and greater abundance of Bifidobacterium species for probiotic compared to placebo [9.1 rRNA genes/g (SD 0/6) vs. 8.8 rRNA genes/g (SD 1.0) mean difference +0.34 rRNA genes/g (95% CI, 0.05 to 0.61, p = 0.019]	LFD† showed greater efficacy in improving GI specific and overall symptoms compared to sham dietary advice at 4 week LFD-induced effects on microbiota can be modified with adjunct probiotic therapy
LFD vs. probiotics
Pederson et al. (18) 2014 Denmark	Randomized, open label control trial	n = 123 Adults aged 18–74 years Rome III Tertiary hospital	6-week LFD or normal diet (ND) or lactobacillus rhamnoses GG probiotic (LGG)	IBS-SSS	LFD reduced IBS-SSS from baseline to 6 weeks compared to LGG vs. ND (p = <0.01) IBS-SSS scores reduced in LFD and LGG group compared to the normal diet (133 ± 122 vs. 68 ± 107, 133 ± 122 vs. 34 ± 95, p = <0.01) at 6 weeks	LFD superior over probiotic alone across all IBS subtypes except IBS-C
LFD vs. non-dietary interventions
Peters et al. (19) 2016 Australia	Randomized open-label, parallel study	n = 74 Adult aged 18 years and over Rome III General IBS population	6-week LFD or gut-directed hypnotherapy or a combination of both	100 mm VAS for symptoms (abdominal bloating, wind, abdominal pain, nausea, and satisfaction with stools)	Improvements in all symptoms were observed from baseline to 6 weeks for hypnotherapy, LFD and combination treatment with no difference across groups (p = 0.67)	While both gut-directed hypnotherapy and LFD were equally efficacious in the short (6 weeks) and longer term (6 months), gut-directed hypnotherapy showed a greater benefit on psychological indices compared to LFD Combining two equally efficacious therapies did not necessarily confer added benefits for IBS patients
Schumann et al. (20) 2018 Germany	Randomized, single blind study	n = 59 Adults aged 18–75 years Rome III Online and local press, department of internal and integrative medicine	12-week LFD or yoga	IBS-SSS	No significant differences between groups regarding IBS-SSS, except for abdominal distention subscale at 12 weeks (p = 0.040) in favor of LFD IBS subtype analysis showed no significant differences between interventions for effectiveness (data not shown)	LFD† showed higher proportion of participants who achieved clinically meaningful reduction in IBS-SSS at 12 weeks Clinical remission was sustained in equal number of patients between both groups at 6-month follow-up

GI, gastrointestinal; GSRS, gastrointestinal symptom rating scale; HFD, high FODMAP diet; IBS-C, irritable bowel syndrome-constipation, IBS-D, irritable bowel syndrome-diarrhea; IBS-M, irritable bowel syndrome-mixed; IBS-SSS, irritable bowel syndrome symptom severity score; NICE, National Institute for Health and Care Excellence; VAS, visual analogue scale; ^†indicates the LFD was superior for treatment response.