Jing 2019.

Study characteristics
Methods	Study design: RCT Setting: China
Participants	State of disease/disease type: unknown CD and UC Inclusion criteria: confirmed diagnosis of IBD Exclusion criteria: intestinal surgery, non‐steroidal drugs within past month, long‐term smoker, pregnancy, hepatic disease, renal disease, calcium or vitamin D supplementation Age: mean: 41.9 years Sex (male:female): 104:94 Number randomised: 99 (Group 1); 99 (Group 2) Number analysed: 99 (Group 1); 99 (Group 2)
Interventions	Group 1: vitamin D 400 IU/day Group 2: no intervention
Outcomes	Duration of follow‐up: 1 month Outcomes 25(OH)D Diamine oxidase D‐lactic acid Endotoxin Interleukin‐1β, interleukin‐6, CRP, TNF‐α
Notes	Funding source: not stated Conflicts of interest: not stated
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Reported as randomised, although method of randomisation was not reported. Quote: "randomly divided".
Allocation concealment (selection bias)	Unclear risk	No information to assess allocation concealment.
Blinding of participants and personnel (performance bias) All outcomes	High risk	Blinding was not reported.
Blinding of outcome assessment (detection bias) All outcomes	High risk	Blinding was not reported.
Incomplete outcome data (attrition bias) All outcomes	Low risk	No withdrawals.
Selective reporting (reporting bias)	Unclear risk	Outcomes reported per methods but no trial registration.
Other bias	Unclear risk	No baseline characteristics reported.