Table 4.

The basic characteristics of the studies and of the studied populations of irritable bowel syndrome (IBS) patients for the studies included to the systematic review.

Ref.	Authors, Year	Design of the Study	Country/Location	Studied Group	Time
[36]	Tazzyman et al., 2015	Randomized, double-blind, placebo-controlled, stratified study	United Kingdom (UK)/Sheffield	Patients with IBS recruited at the University of Sheffield	From January 2014 to April 2014
[37]	Abbasnezhad et al., 2016	Randomized, double-blind placebo-controlled clinical trial	Iran/Ahvaz	Patients with IBS from the outpatient clinic at the Jundishapur University of Medical Sciences	From February to March 2015
[38]	Jalili et al., 2016	Factorial blinded randomized clinical trial	Iran/Tehran	Women with IBS from the Endoscopy Clinic, Shariati Hospital	From 2013
[39]	Jalili et al., 2019	Randomized, double-blind, placebo-controlled clinical trial	Iran/Tehran *	Women with IBS recruited from two gastroenterology clinics	From October 2013 to January 2016
[40]	Sikaroudi et al., 2020	Randomized, double-blind, placebo-controlled trial study	Iran/Tehran	Patients with IBS-D recruited from Rasoul-e-Akram Hospital	February 2017 to May 2018
[41]	Williams et al., 2021	Randomized, double-blind, placebo-controlled study	United Kingdom	Patients with IBS recruited through the University of Sheffield, via the IBS Network	December 2017 to March 2019

* data provided on request; IBS—Irritable Bowel Syndrome; IBS-D—diarrhea-predominant Irritable Bowel Syndrome.