Table 1.

The basic characteristics of the studies and of the studied populations of inflammatory bowel disease (IBD) patients for the studies included to the systematic review.

Ref.	Authors, Year	Design of the Study	Country/Location	Studied Group	Time
[32]	Yang et al., 2013	Open labelled, prospective clinical trial	United States of America (USA)/Pennsylvania	Patients with confirmed Crohn’s disease from Pennsylvania State University	Not specified
[33]	Kabbani et al., 2016	Longitudinal study	United States of America (USA)/Pittsburgh	Patients with Inflammatory Bowel Diseases from the University of Pittsburgh Medical Center	From 1 January 2009 to 31 December 2013
[34]	Narula et al., 2017	Randomized, double-blind placebo-controlled trial	Canada/Ontario	Patients with confirmed Crohn’s disease from McMaster University Medical Centre in Hamilton	From January 2014 to March 2015
[35]	Karimi et al., 2019	Randomized, double-blind clinical trial	Iran/Tehran	Patients with mild to moderate Ulcerative Colitis with vitamin D deficiency referring to Shahid Fayyaz-Bakhsh Hospital, and a private gastroenterology clinic	Not specified