Table 3.

Researches on the influence of synbiotics on IBS patients.

Paper	Research Type	Participants Selection Criteria	Participants 1	IBS Subtype	Preparation (Dosage)	Placebo/Control (Dosage)	Duration	Outcomes
Min et al. (2012) [141]	The randomized, double-blind, controlled trial	Rome III	117 males/females 18–70 y 2	All	Yogurt with standard strains S. thermophilus (≥3 × 109 cfu 3/bottle) and Lb. acidophilus (≥109 cfu/bottle) with the addition of Bifidobacterium animalis subsp. lactis Bb-12 (≥1011 cfu/bottle), Bifidobacterium enhancer, and acacia dietary fiber	Yogurt with standard strains S. thermophilus (≥3 × 109 cfu/bottle) and Lb. acidophilus (≥109 cfu/bottle) with the addition of Bifidobacterium animalis subsp. lactis Bb-12 (≥1011 cfu/bottle)	8 weeks	Improvement in bowel habits and IBS symptoms
Cappello et al. (2013) [134]	The parallel-group, double-blinded, placebo-controlled study	Rome III	64 males/females 18–75 y	wd 4	Probinul ® (5 × 109 Lb. plantarum, 2 × 109 Lb. casei subp. rhamnosus, 2 × 109 Lb. gasseri, 1 × 109 B. infantis, 1 × 109 B. longum, 1 × 109 Lb. acidophilus, 1 × 109 Lb. salivarus, 1 × 109 Lb. sporogenes, 5 × 109 S. thermophilus, 2 g inulin, 1.3 g tapioca-resistant starch) twice 5 g/d 5	No data on used compounds product by CaDi Group (Rome, Italy)	2 weeks prior to synbiotic/placebo administration, then 4 weeks of treatment	Decreased flatulenceThe increased transition time of intestinal content Improved in self-scored quality of IBS patients’ life No overall relief of symptoms
Bucci et al. (2014) [137]	The parallel-group, double-blinded, randomized, placebo-controlled study (core study) and the open-label prospective, partially controlled	Rome III	64 males/females 18–75 y	wd	Probinul® twice 5 g/d (during extension period only 2 weeks/month)	Lack of information	4 weeks of core study, then 6 months of the extension period	Decreased flatulence even during cyclic administration
Rogha et al. (2014) [54]	The randomized, double-blinded, placebo-controlled trial	Rome III	56 males/females The average age of 39.8 ± 12.7	wd	Lactol® (1.5 × 108 spores of B. coagulans and FOS) 100 mg	Lactose starch and tartazine 100 mg	12 weeks	Relief from abdominal pain/discomfort and diarrhea
Shavakhi et al. (2014) [135]	The randomized, placebo-controlled, triple-blinded study	Rome II	129 males/females average age of 36.2 ± 9.3	wd	Balance® (FOS, magnesium stearate, hydroxypropyl methyl cellulose, Lb. casei, Lb. rhamnosus, Lb. acidophilus, Lb. bulgaricus, B. breve, B. longum, S. thermophilus; a total of 1 × 108 cfu/capsule) 2 capsules a day	No data on used compounds 2 capsules a day	14 days	No effect of treatment
Bogovič Matijašic et al. (2016) [136]	The double-blind, randomized, placebo-controlled multicenter trial	Rome III	30 subjects 18–65 y	IBS-C	Fermented milk (starter culture: S. thermophilus ABT-21, probiotics: 1.8 × 107 cfu/g Lb acidophilus La-5, 2.5 × 107 cfu/g B. lactis BB-12, 2% dietary fiber Beneo Orafti Synergy1—90% inulin, 10% oligofructose) 360 g/d	Heat-treated fermented milk without probiotic bacteria and dietary fibers 360 g/d	2 weeks run-in period, then 4 weeks of treatment, and 2 weeks of follow-up	Increased abundance of used probiotic strains in subjects’ fecal samples Transient colonization of used probiotics The abundance of the Enterobacteriaceae family was not affected No significant changes in fecal microbiota
Moser et al. (2019) [139]	Pilot study	Individual protocol	10 males/females 37–53 y	IBS-D	OMNi-BiOTiC® Stress Repair (corn starch, maltodextrin, inulin, FOS, potassium chloride, magnesium sulfate, mangan sulfate, enzymes, 7.5 × 109 of each strain: Lb. casei W56, Lb. acidophilus W22, Lb. paracasei W20, Lb. salivarius W24, Lb. plantarum W62, L. lactis W19, B. lactis W51, B. lactis W52, B. bifidum W23)	na 6	4 weeks	Increased phylogenetic diversity of gastric and duodenal microbiota Reduced number of CD4+ T cells in the ascending colon Higher levels of acetate and butyrate in fecal samples
Lee et al. (2019) [140]	The single-center, randomized, double-blind, placebo-controlled clinical trial	Rome III	28 males/females ≥19 y	All	Ultra-Probiotics-500 (1 × 1013 cfu of probiotic strains: Lactobacillus (rhamnosus, acidophilus, casei, bulgaricus, plantarum, and salivarius), Bifidobacterium (bifidum and longum, 175 mg of FOS, 150 mg of Ulmus davidiana, 10 mg of Geum urbanum, and 100 mg of inulin) 1 capsule/d (low-dose group)2 capsules/d (high-dose group)	The same material used for encapsulation. No data on used compounds. 1 capsule/d (low-dose group) 2 capsules/d (placebo group)	8 weeks	No dose-dependent effects Decrease the fatigue in IBS individuals (high-dose) Relief in abdominal pain/discomfort, bloating, stool patterns
Bahrudin et al. (2020) [142]	The prospective, double-blind, randomized, controlled trial	Rome III	163 males/females 22–37 y	IBS-C	Synbiotic drink (water, sugar, skimmed milk powder (cow), stabilizers (polydextrose), fermented milk (water, acidity regulator, skimmed milk powder (cow), and lactobacillus), acidity regulators, soybean fiber, and flavoring) with Lb. helveticus and 1.5 g/100 mL polydextrose 350 mL/d 5	Probiotic drink ((water, sugar, skimmed milk powder (cow), stabilizers (polydextrose), fermented milk (water, acidity regulator, skimmed milk powder (cow), and lactobacillus), acidity regulators, soybean fiber, and flavoring)) with Lb. helveticus 350 mL/d	1 week	Shortened intestinal transition time Reduced fecal pH Relief in constipation-related symptoms No difference between synbiotic and control group—probiotic alone conferred a health benefit
Seong et al. (2020) [144]	Animal study	na	20 male Wistar rats (weight: 350 ± 50 g) aged 8 weeks	na	Treatment group 1—maltodextrin, 1 × 1010 cfu/g Lb. paracasei DKGF; Treatment group 2—maltodextrin, 1 × 1010 cfu/g Lb. paracasei DKGF, 10.0 mg (w/w) Opuntia extract; Treatment group 3—maltodextrin, 1 × 1010 cfu/g Lb. paracasei DKGF, 30.0 mg (w/w) Opuntia extract	Maltodextrin	4 weeks	Improved stool consistency (better in synbiotic groups) Decreased serum corticosterone levels (lower in synbiotic groups) Low levels of TNF-α 7 in the colonic mucosa (both synbiotic and probiotic groups) Increased expression of the tight junction proteins (higher in synbiotic groups) Higher abundance of Lb. paracasei in fecal samples (more significant difference in synbiotic groups)
Skrzydło-Radomańska et al. (2021) [143]	The randomized, double-blind, placebo-controlled, parallel group trial	Rome III	68 males/females 18–60 y	IBS-D	Synbiotic containing a total of 5.0 × 109 probiotic strains (B. lactis DSMZ 32269, B. longum DSMZ 32946, B. bifidum DSMZ 32403, Lb. rhamnosus FloraActive 19070-2, Lb. acidophilus DSMZ 32418) and 947 mg of scFOS 2 sachet/d	978 mg of maltodextrin2 sachet/d	2 weeks screening period, then 8 weeks of treatment	Attenuation of IBS symptoms (pain, flatulence, stool pressure, feeling of incomplete bowel movements) Decreased severity of IBS symptoms

¹ the final (after screening) number of participants who received treatment is given; ² years old; ³ colony-forming units; ⁴ without differentiation; ⁵ not applicable; ⁶ milliliters per day; ⁷ tumor necrosis factor α.