Methods	Randomised, double blind, placebo controlled trial. Trial duration: 12 months
Participants	Participants (n = 49) with rheumatoid arthritis of at least two years’ duration (average duration of disease 7 years). Mean age 52 years (range 18 to 69 years), 68% female
Interventions	100 000 IU calciferol (no more details given) per day (n = 24) Placebo (n = 25)
Outcomes	Consumption of analgesics and antiinflammatory medicines, all cause withdrawals, and other outcomes
Notes	Oxford Quality Score: R1, D1, W1 = 3/5 Oxford Pain Validity Score: 11/16
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Stated to be randomised. One of the authors chose whether participants received placebo or active treatment, but it is not stated by which method
Allocation concealment (selection bias)	Unclear risk	One of the authors chose whether patients received placebo or active treatment (though it is not stated how) and was therefore possibly aware of the allocation. However, the authors arrived at their assessments independently and the other author’s opinion (not aware of allocation or blood calcium data) was adopted in case of disagreement
Blinding (performance bias and detection bias) All outcomes	Unclear risk	Stated to be double blind. One of the authors was blinded but the other was possibly aware of treatment allocation