Mitri 2011.

Study characteristics
Methods	16‐week factorial randomised controlled trial Randomisation by permuted blocks using computer‐generated random‐number sequence, no further details provided States double‐masked design 88 of 92 completed
Participants	92 participants (47 women, 45 men), community‐based study, Boston, USA, mean age 57 years Inclusion criteria: ambulatory, ≥ 40 years of age and with a BMI (kg/m2) ≥ 25 (≥ 23 if Asian) with glucose intolerance or early diabetes, defined as a fasting plasma glucose concentration ≥ 100 mg/dL or 2‐h glucose concentration ≥140 mg/dL after 75 g oral dextrose or glycated haemoglobin (Hb A1c) ≥ 5.8% Exclusion criteria: BMI > 40, Hb A1c > 7%, self‐reported diabetes treated with pharmacotherapy, weight change > 4 kg over the previous 6 months, use of supplements that contained vitamin D or calcium in ≤ 8 weeks of screening and an unwillingness to discontinue supplementation for ≥ 2 weeks before the study initiation and during the study; hyperparathyroidism, hypercalcemia, nephrolithiasis, chronic kidney disease, conditions that may have affected vitamin D or calcium metabolism (eg, sarcoidosis), and regular visits to tanning booths
Interventions	1. 2000 IU vitamin D3 and 800 mg calcium (as 2 doses calcium carbonate) daily 2. 2000 IU vitamin D3 and 2 placebos daily 3. 800 mg calcium (as calcium carbonate) and 1 placebo daily 4. Matching placebos Randomised 23; 23; 22; 24 Completed 23; 22; 21; 22 Duration of treatment 16 weeks
Outcomes	Measured over a period of 16 weeks 1. Number of persons sustaining new non‐vertebral fracture 2. Numbers of persons sustaining hypercalcaemia or kidney stone
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	States "computer‐generated random‐number sequence"
Allocation concealment (selection bias)	Unclear risk	States "randomly assigned", no other information provided