Table 1. Studies reporting sex differences in the efficacy of probiotics in irritable bowel syndrome

Reference	Country	Patients	Probioticsa	CFU	Total		Treatment group		Control group		Duration	Primary outcome	Results
					Male	Female	Male	Female	Male	Female
Enck et al., (2008)	Germany	N/A	E. coli DSM 17252,E. faecalis DSM 16440	1.35 × 108-4.05 × 108	150	147	77	72	73	75	8 weeks	Global symptoms and abdominal pain	NNT: males 2.49 (1.76-4.22), females 3.98 (2.55-9.13)
Enck et al., (2009)	Germany	N/A	E. coli DSM 17252	6.8 × 107-2.0 × 108	151	147	76	72	75	75	8 weeks	Global symptoms and abdominal pain	Responder rate: males 22.6% vs 7.2%, females 15.5% vs 2.5%
Ludidi et al., (2014)	The Netherlands	Rome III	L. casei W56,L. salivarius W57,L. lactis W58,L. acidophilus NCFM,L. rhamnosus W71	5.0 × 109	13	27	6	15	7	12	6 weeks	Abdominal pain (visceral perception)	MSS: males −1.18 (−1.80 to −0.25) vs 0.93 (−3.87 to 1.43), females −0.06 (−3.77 to 1.64) vs −1.49 (−7.42 to −0.32)
Mack et al., (2022)	Germany	Rome III	E. coli DSM 17252,E. faecalis DSM 16440	1.3 × 108-3.9 × 108	187	197	56	131	63	134	26 weeks	Global symptoms and abdominal pain	IBS-GAI: males 16.1% vs 17.2%, females 18.0% vs 13.1%
Quigley et al., (2023)	US, UK/Ireland	Rome IV	B.hydrogenotrophica	2.0 × 1010-2.0 × 1011	96	269	50	127	46	142	8 weeks	Bowel habit and abdominal pain	Overall response: males 19.1% vs 20.0%, females 26.0% vs 16.7%
Preston et al., (2018)	US, Canada	Rome III	L. acidophilus CL1285,L. casei LBC80R,L. rhamnosus CLR2	1.0 × 1011	45	68	16	21	29	47	12 weeks	Global symptoms and abdominal pain	Improvement in QOL; IBS-D only in males
Chang et al., (2024)	South Korea	Rome III	B. longum IDCC 4101,B. bifidum IDCC 4201, B. lactis IDCC 4301,B. breve IDCC 4401,E. faecium IDCC 2102,L. rhamnosus IDCC 3201,L. acidophilus IDCC 3302,L. casei IDCC 3451,L. plantarum IDCC 3501,L. helveticus IDCC 3801	1.0 × 1010	39	53	26	21	13	32	4 weeks	Global symptoms	Overall IBS symptom relief: males 3.54 ± 0.42 vs 2.69 ± 0.44, females 3.48 ± 0.32 vs 2.40 ± 0.28

Studies listing multiple probiotic strains represent multi-strain probiotic formulations.
CFU, colony-forming unit; NA, not applicable; NNT, number needed to treat; MSS, mean symptom score; IBS-GA, irritable bowel syndrome-global assessment of improvement; QOL, quality of life; IBS-D, diarrhea-predominant irritable bowel syndrome.