Table 1.

Characteristics of studies included in the meta-analysis.

	First Author, Year	Country	Study Design	Sample	Intervention	Control	Duration of Therapy	Outcome Measures	Risk of Bias
				1. Sample size, n	N a	1. Intervention (n) a		Symptoms
				2. Age, mean [SD] (range)				Quality of life
				3. Female,%				BSFS
				4. Diagnostic criteria				Stool frequency
				5. IBS subtype
				6. Drop out
1	Goyal, 2021 [19]	India	RCT, single-blind	1. 101	n = 51	Traditional dietary advice (n = 49)	4 weeks	Symptoms	Good
				2. 41.9 [17.1]				QoL
				3. 42%				BSFS
				4. Rome IV				Stool frequency
				5. IBS-D
				6. 1
2	Krieger, 2020 [20]	Switzer-land	RCT, cross-over	1. 29	n = 22	Low-lactose diet (n = 24)	3 weeks	Symptoms	Fair
				2. 30 (18–62)
				3. 89.7%				BSFS
				4. Rome IV
				5. NA
				6. 5
3	Wilson, 2020 [21]	United Kingdom	RCT	1. 45	n = 22	Sham diet (n = 23)	4 weeks	Symptoms	Good
				2. 38.9 [10.0]				QoL
				3. 55.1%
				4. Rome III				Stool frequency
				5. NA
				6. 6
4	Guerreiro, 2020 [22]	Portugal	Non-RCT	1. 70	n = 47	NICE guidelines (n = 23)	4 weeks	Symptoms	Good
				2. 48.5 [14.7]
				3. 74.3%
				4. Rome IV
				5. All types; IBS-D (42.1%)
				6. 13
5	Catinean, 2019 [23]	Romania	RCT	1. 60	n = 30	Nutraceutical agent (n = 30)	24 days	Symptoms	Weak
				2. 40.37 [11.95]
				3. 55%
				4. Rome III
				5. Excluding IBS-C
				6. NR
6	Paduano, 2019 [24]	Italy	Non-RCT, consecutive controlled study	1. 42	n = 34	Gluten-free (n = 30), Balanced Mediterranean diet (n = 28)	4 weeks	Symptoms	Fair
				2. 28.62 [6.86]				QoL
				3. 83.3%
				4. Rome IV
				5, All type; IBS-D (52.4%)
				6. 14
7	Patcharatrakul, 2019 [25]	Thailand	RCT, single-blind	1. 66	n = 30	Brief advice on a commonly recommended diet (n = 32)	4 weeks	Symptoms	Fair
				2. 50 [13.7]
				3. 76.7%
				4. Rome III
				5. All types; IBS-C (51.6%)
				6. 4
8	Zahedi, 2018 [26]	Iran	RCT, single-blind	1. 110	n = 50	General dietary advice in BDA (n = 51)	6 weeks	Symptoms	Good
				2. 37.6 [11.09]				QoL
				3. 50.5%				BSFS
				4. Rome II				Stool frequency
				5. IBS-D
				6. 9
9	Schumann, 2018 [27]	Germany	RCT, single-blind	1. 59	n = 25	Yoga (n = 27)	12 weeks	Symptoms	Good
				2. 56.33 [9.5]				QoL
				3. 88.1%
				4. Rome III
				5. All types; IBS-D (44.1%)
				6. 7
10	Pirkola, 2018 [28]	Finland	RCT, cross-over	1. 9	n = 7	Regular rye bread (n = 7)	1 day	Symptoms	Good
				2. 39 (29–51)
				3. 100%
				4. Rome III
				5. All types; IBS-D (42.9%)
				6. 2
11	Eswaran, 2017 [29]	United States of America	RCT	1. 91	n = 45	Modified NICE guidelines (n = 39)	4 weeks	QoL	Good
				2. 42.6 (19–75)
				3. 71%
				4. Rome III
				5. IBS-D
				6. 7
12	Harvie, 2017 [30]	New Zealand	RCT, non-blind	1. 50	n = 20	No dietary education (n = 25)	3 months	Symptoms	Good
				2. 43.3 [13.8]				QoL
				3. 86%				BSFS
				4. Rome III				Stool frequency
				5. All types; IBS-D (62%)
				6. 5
13	Staudacher, 2017 [31]	Unitied Kingdom	RCT, 2 × 2 factorial design	1. 104	n = 51	Sham diet (n = 53)	4 weeks	Symptoms	Good
				2. 36 [11]				QoL
				3. 67.3%				BSFS
				4. Rome III				Stool frequency
				5. Excluding IBS-C; IBS-D (66.3%)
				6. 17
14	McIntosh, 2017 [32]	Canada	RCT, single-blind	1. 40	n = 19	High-FODMAP (n = 18)	3 weeks	Symptoms	Good
				2. 50.28 (26–77)
				3. 59.5%
				4. Rome III
				5. All types; IBS-D (27.8%)
				6. 3
15	Laatikainen, 2016 [33]	United States of America	RCT, cross-over	1. 80	n = 37	Traditional rye bread (n = 36)	4 weeks	Symptoms	Good
				2. 42.9 (21–64)				QoL
				3. 91.3%
				4. Rome III
				5. Excluding IBS-C
				6. 7
16	Eswaran, 2016 [34]	United States of America	RCT	1. 92	n = 43	Modified NICE Guidelines (n = 39)	4 weeks	Symptoms	Good
				2. 42.6 (19–75)
				3. 71%				BSFS
				4. Rome III				Stool frequency
				5. IBS-D
				6. 8
17	Peters, 2016 [35]	Australia	RCT, non-blind	1. 39	n = 21	Gut-directed hypnotherapy (n = 18)	6 weeks	Symptoms	Good
				2. 34 (23–66)				QoL
				3. 81.1%
				4. Rome III
				5. All types; IBS-D (40.5%)
				6. 12
18	Böhn, 2015 [36]	Sweden	RCT, single-blind	1. 75	n = 33	NICE and the BDA guidelines (n = 34)	4 weeks	Symptoms	Good
				2. 43 [16]
				3. 83.6%				BSFS
				4. Rome III
				5. All types; IBS-D (24%)
				6. 8
19	Pedersen, 2014 [37]	Denmark	RCT, non-blind	1. 123	n = 34	Probiotic Lactobacillus rhamnosus GG (n = 37), Normal Danish/Western diet (n = 37)	6 weeks	Symptoms	Good
				2. 37 (18–74)				QoL
				3. 73%
				4. Rome III
				5. All types; IBS-D (40.7%)
				6.15
20	Halmos, 2014 [38]	Australia	RCT, cross-over	1. 33	n = 30	Typical Australian diet (n = 30)	3 weeks	Symptoms	Good
				2. 41 (29–53)
				3. 70%
				4. Rome III
				5. All types; IBS-D (33.3%)
				6. 3
21	Staudacher, 2011 [39]	United Kingdom	RCT	1. 41	n = 16	Habitual diet (n = 19)	4 weeks	Symptoms	Good
				2. 35.2 [11.4]
				3. 65.9%				BSFS
				4. Rome III				Stool frequency
				5. Excluding IBS-C
				6. 6
22	Ong, 2010 [40]	Australia	RCT, single-blind, cross-over	1. 15	n = 15	High-FODMAP diet (n = 15)	2 days	Symptoms	Good
				2. 41 (22–59)
				3. 86.7%
				4. Rome III
				5. All types; IBS-D (26.7%)
				6. NR

BDA, British Dietetic Association; BSFS, Bristol stool form score; NA, not assessed; NICE, National Institute for Health and Care Excellence; NR, not reported; RCT, randomized controlled trial; QoL, quality of life; SD, standard deviation. ^a Numbers are retrieved from per-protocol data