Table 2.

Characteristics of studies included in the meta-analysis

Trial	Type of IBS	Criteria	Age (yr)		Sex (Male/Female)		Probiotic	Probiotic dosage	Duration of treatment	Follow-up	Outcome
			Probiotic	Placebo	Probiotic	Placebo
Kajander et al[33]	All types	Rome II	50	46	2/41	4/39	Lactobacillusrhamnosus GG	1 × 107 CFU	20 wk	3 wk	↑ Stabilization of intestinal microbiota
							L. rhamnosus Lc705				↓ Distension and abdominal pain in probiotic group
							Propionibacteriumfreudenreichiissp. shermanii JS				↓ IBS symptoms
							Bifidobacteriumanimalisssp. lactis Bb-12
Williams et al[32]	All types	Rome II	40	38	3/25	8/20	L. acidophilus CUL60	2.5 × 1010 CFU	8 wk	2 wk	↑ QoL
							L. acidophilus CUL21				↓ Symptom severity, bloating not improved
							B. lactis CUL34,
							B. bifidum CUL20
Zeng et al[39]	D-IBS	Rome II	44.6	45.8	10/4	9/6	Streptococcusthermophilus	1 × 108 CFU	4 wk	-	Mucosal barrier function and bowel symptoms improved
							L. bulgaricus	1 × 107 CFU			↓ Small bowel permeability
							L. acidophilus
							B. longum
Enck et al[35]	All types	ICHPPC and WONCA	49.8	49.4	76/72	75/75	Escherichia coli (Symbioflor 2)	1.5-4.5 ×107 CFU	8 wk	ND	↓ Typical symptoms of IBS patients
Drouault-Holowacz et al[37]	All types	Rome II	47	44	8/40	16/36	B. longum LA101	1 × 1010 CFU	4 wk	-	↑ QoL
							L. acidophilus LA102				↓ Flatulence
							Lactococcusl actis LA103				↓ Abdominal pain and bloating
							S. thermophilus LA104
Sinn et al[42]	All types	Rome III	41.9	47.5	6/14	8/12	L. acidophilus SDC 2012, 2013	2 × 109 CFU	4 wk	-	↓ IBS symptoms, abdominal pain and discomfort
Enck et al[36]	All types	ICHPPC and WONCA	49.8	49.4	77/72	73/75	E. coli and Enterococcusfaecalis (Pro Symbioflor)	3-9 × 107 CFU	8 wk	-	↓ 50% global symptom score and abdominal pain score
Simrén et al[40]	All types	Rome II	42	44	11/26	11/26	L. paracasei F19	5 × 107 CFU	8 wk	8 wk	Improvement in both groups in pain frequency, pain and bloating severity, satisfaction with bowel habits, and interference with daily life
							L. acidophilus La5
							B. lactis Bb-12
Sondergaard et al[43]	ND	Rome II	53.9	48.5	7/20	6/19	L. paracasei F19	5 × 107 CFU	8 wk	8 wk	Symptom relief in both groups;no difference between probiotics and placebo
							L. acidophilus La5	(500 mL)
							B. lactis Bb-12
Guglielmetti et al[44]	All types	Rome III	36.65	40.98	21/41	19/41	B. bifidum MIMBb75	1 × 109 CFU	4 wk	4 wk	↓ IBS symptoms like: pain, discomfort distension, bloating, digestive disorders
											↑ QoL
Ducrotté et al[45]	D-IBS (in majority of patients)	Rome III	36.53	38.4	70/38	81/25	L. plantarum 299v	1 × 1010 CFU	4 wk	3 wk	↓ Abdominal pain and bloating
Kruis et al[34]	D-IBS	Rome II	46.3	45.1	12/48	16/44	E. coli (Nissle 1917)	2.5-25 × 109 CFU	12 wk	-	No significant effects of probiotics in general symptoms, but enteric flora altered due to gastroenterocolitis or administration of antibiotics before IBS initiation
Ki Cha et al[38]	D-IBS	Rome III	37.9	40.3	12/13	14/11	L. acidophilus	1 × 1010 CFU	8 wk	2 wk	↑ QoL
							L. plantarum
							L. rhamnosus
							B. breve
							B. lactis
							B. longum
							S. thermophilus
Dapoigny et al[46]	All types	Rome III	46.1	48.8	5/20	10/15	L. caseirhamnosus (LCR 35)	6 × 108 CFU	4 wk	2 wk	↓ IBS patients complaining of diarrhea
								(250 mg)			↓ 50% reduction in IBS severity score in probiotic arm
Roberts et al[41]	C-IBS, A-IBS	Rome III	44.66	43.71	14/74	14/77	B. lactis CNCMI-2494	1.25 × 1010 CFU	12 wk	-	Significant improvement in IBS symptoms in both groups

A-IBS: Alternating irritable bowel syndrome; CFU: Colony forming unit; IBS: Irritable bowel syndrome; C-IBS: Constipation-predominant irritable bowel syndrome; D-IBS: Diarrhea-predominant irritable bowel syndrome; ICHPPC: International classification of health problems in primary care; ND: Not determined; QOL: Quality of life; WONCA: World organization of family doctors.