Table 2.

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

Ref.	Participants (Female Participants) Number	Age (Mean ± SD/Range)	Inclusion/Exclusion Criteria
[32]	18 (11)	38.0 ± 17.0 years	Inclusion: aged 18–70; confirmed Crohn’s disease; CDAI scores 150–400; serum levels of 25(OH)D < 40 ng/mL Exclusion: ulcerative colitis; any other inflammatory bowel conditions; ostomy; receiving corticosteroid therapy
[33]	965 (505)	44.0 ± 10.1 years	Inclusion: confirmed inflammatory bowel disease; being patient at the University of Pittsburgh Medical Center from 1 January 2009 to 31 December 2013 Exclusion: -
[34]	34 (20)—at baseline	According to group: 35.0 ± 3.0. years (low-dose of vitamin D supplementation) 33.0 ± 3.0 years (high-dose of vitamin D supplementation)	Inclusion: aged 18–70, diagnosis of Crohn’s disease; clinical remission for at least 28 days with a HBI of ≤ 4; maintenance therapies for Crohn’s disease at a stable dose for at least 3 months; used vitamin D supplements at the time of enrolment discontinued for a period of at least 6 weeks Exclusion: systemic steroid therapy in the preceding 4 weeks; pregnancy or considering pregnancy during the study period; short-gut syndrome; any condition which could predispose to vitamin D toxicity, including renal insufficiency, sarcoidosis, hyperparathyroidism, or malignancy; therapy with thiazide diuretics, barbiturates, digitalis, or supplemental products containing vitamin D
[35]	46 (22)	According to group: 39.7 ± 15.6 years (low-dose of vitamin D supplementation) 34.0 ± 12.5 years (high-dose of vitamin D supplementation)	Inclusion: aged ≥ 18 years; histopathologic diagnosis of mild to moderate ulcerative colitis (diagnosis of the severity based on physician’s judgment); vitamin D deficiency (<75 nmol/L); no change in the type and dosage of their medicine over the past month Exclusion: other diseases; intestinal disorders; known autoimmune diseases; cancer; inflammatory and infectious diseases; using vitamin D supplements, mineral-multivitamins, omega-3, polyphenolic and antioxidant medications, anticoagulants, non-steroid anti-inflammatory drugs, antihistamines and calcium channel antagonists during the past month; pregnancy; breastfeeding; in women—using contraceptives; changes in the type and dosage of the drugs during the study

CDAI—Crohn’s Disease Activity Index; HBI—Harvey-Bradshaw Index.