Bafutto 2020.

Study characteristics
Methods	Study design: RCT (abstract) Setting: Brazil
Participants	State of disease/disease type: active CD Inclusion criteria: adults (aged 18–70 years) with moderate‐to‐severe CD on anti‐TNF therapy and 25(OH)D < 30 ng/mL Exclusion criteria: pregnancy, chronic kidney or liver disease, sarcoidosis, tuberculosis, hyper‐ or hypoparathyroidism, neoplasia, use of anticonvulsants, received calcium or vitamin D supplementation within preceding 6 months Age: mean: 41 years (Group 1); 37 (Group 2); 33 years (Group 3) Sex (males): 20% (Group 1); 80% (Group 2); 50% (Group 3) Number randomised: 10 (Group 1); 10 (Group 2); 10 (Group 3) Number analysed: not stated
Interventions	Group 1: vitamin D 2000 IU/week for 8 weeks Group 2: vitamin D 10,000 IU/week for 8 weeks Group 3: vitamin D 50,000 IU/week for 8 weeks
Outcomes	Duration of follow‐up: 52 weeks Outcomes Clinical relapse (CDAI > 150, calprotectin > 300 µg/g, CT evidence of inflammation) Vitamin D concentration CRP Faecal calprotectin Quality of life
Notes	Funding source: none Conflicts of interest: none
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Reported as randomised, although method of randomisation was not reported.
Allocation concealment (selection bias)	Unclear risk	No information to assess allocation concealment.
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Reported as double‐blind trial, although method of blinding was not reported.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Reported as double‐blind trial, although method of blinding was not reported.
Incomplete outcome data (attrition bias) All outcomes	Low risk	All participants completed intervention period of 8 weeks.
Selective reporting (reporting bias)	Unclear risk	All outcomes from methods reported, no clinical trial registration.
Other bias	Low risk	Balanced baseline characteristics and no other concerns.