Table 2.

Studies on the effect of prebiotics on IBS individuals.

Paper	Research Type	Participants Selection Criteria	Participants 1	IBS Subtype	Preparation (Dosage)	Placebo/Control (Dosage)	Duration	Outcomes
Hunter et al. (1999) [52]	The randomized, controlled, double-blind, crossover study	Individual protocol	21 males/females 18–65 y 2	wd 3	Oligofructose (Raftilose P95) three times 2 g/d 4	Sucrose three times 1 g/d	First 2 weeks of normal diet, then 2 weeks of controlled standard UK diet (45% carbohydrate, 40% fat, and 15% protein)	No significant results
Olesen et al. (2000) [128]	The prospective, randomized, placebo-controlled, single-blind, and double-blind phases	Manning	98 males/females 18–70 y	wd	FOS 5 10 g/d (2 weeks)/20 g/d (next 10 weeks)	Glucose 10 g (2 weeks)/20 g/d (next 10 weeks)	First 2 weeks of single-blind phase (only placebo), then 12 weeks of double-blind phase (prebiotic/placebo)	FOS may increase the severity of IBS symptoms; however, patients might adapt after prolonged usage
Silk et al. (2009) [130]	The single-center, parallel, patient blinded, randomized, crossover, placebo-controlled trial	Rome II	44 males/females 20–79 y	All	trans-GOS 6 3.5 or 7.0 g/d	Maltodextrins DE 20 3.5 or 7.0 g/d	Baseline period—2 weeks (only placebo); next phase—3 months (prebiotic/placebo)	Increased number of Bifidobacterium spp. to a level comparable with healthy people (both doses of GOS) Increased number of Eubacterium rectale/C.coccoides (GOS dose of 3.5 g/d) Reduced number of C. perfringens (GOS dose of 7.0 g) Changes in the consistency of feces, flatulence, and overall improvement of IBS symptoms (GOS) The reduced anxiety level in the IBS-D group (GOS dose of 7.0 g/d)
Azpiroz et al. (2016) [129]	The parallel, placebo-controlled, randomized, double-blind study	Rome III	79 males/females 18–60 y	All	scFOS two times 2.5 g/d	Maltodextrins two times 2.5 g/d	28 days	Increased number of Bifidobacterium spp. Decreased level of anxiety Attenuated severity of IBS symptoms No effect on rectal hypersensitivity
Niv et al. (2016) [132]	The prospective, randomized, double-blind, placebo-controlled study	Rome III	108 males/females 18–77 y	All	PHGG 3 g/d (first week)/6 g/d (11 weeks)	Maltodextrin 3 g/d (first week)/6 g/d (11 weeks)	First 2 weeks without prebiotic/placebo, next 12 weeks of product administration, then 4 weeks of follow-up	Improvement on bloating and gasses
Chen et al. (2017) [131]	Animal study	na 7	60 four-week-old female specific pathogen-free (SPF) C57BL/6 mice	na PI-IBS 8 model	The PB (FOS, GOS, inulin, and anthocyanins) 1.26 mg/g body weight	Saline/healthy control group	8 weeks of preventive administration of the PB/saline before infection with Trichinella spiralis larvae, then 8 weeks for recovery without prebiotic	Faster recovery from body weight loss Pretreatment with PB could help to improve the well-being of PI-IBS patients PB can diminish inflammation both in the Caco-2 cells and the IBS mice model Protection of intestinal barrier integrity PB could help protect the homeostasis of GIT microbiota

¹ the final (after screening) number of participants who received treatment is given; ² years old; ³ without differentiation; ⁴ gram per day; ⁵ fructooligosaccharides; ⁶ galactooligosaccharides; ⁷ not applicable; ⁸ post-infection IBS.