Reid 2005.

Study characteristics
Methods	Double‐blind, randomised, controlled trial The trial was conducted in New Zealand.
Participants	Healthy postmenopausal women more than 5 years from postmenopause Age: more than 55 years (mean age, 74 years) Mean baseline weight: 67 kg Mean baseline blood pressure:134/70 mmHg Exclusion criteria: participants receiving therapy for osteoporosis or taking calcium supplements, major ongoing disease including serum creatinine greater than 1.8 mg/dL (0.2 mmol/litre), untreated hypo‐ or hyperthyroidism, liver disease, serum 25‐hydroxyvitamin D below 10 g/litre (25 nmol/litre), malignancy, or metabolic bone disease, users of hormone replacement therapy, anabolic steroids, glucocorticoids, or bisphosphonate in the previous 1 year
Interventions	Intervention group: calcium as calcium citrate (1 gm of elemental calcium a day; n = 732) Control group: identical placebo (n = 739) Trial duration 30 months
Outcomes	Primary outcome: fracture incidence Secondary analysis: ‐ Body weight ‐ Blood pressure
Notes	Dietary calcium intake was assessed using a validated food frequency questionnaire. Calcium was provided by Citracal, Mission Pharmacal, San Antonio TX.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	"Treatments were allocated randomly using a minimisation algorithm balancing for current thiazide use, age, and the occurrence of fractures resulting from minimal trauma after the age of 40 years".
Allocation concealment (selection bias)	Unclear risk	Not described
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Double‐blinded study. "Subjects received 1 g elemental calcium daily as citrate (Citracal, Mission Pharmacal, San Antonio TX) or an identical placebo".
Blinding of outcome assessment (detection bias) All outcomes	Low risk	"Blood pressure was measured using a Dinamap automatic monitor (Johnson & Johnson, Tampa, FL) at each visit".
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Dropouts were not reported.
Selective reporting (reporting bias)	Low risk	A variety of preplanned models were run: an intention‐to‐treat analysis, with and without imputation (maximum likelihood) of missing values, and with and without adjustment for compliance; a per protocol analysis; and an analysis of the change in blood pressure, excluding those taking blood pressure‐lowering medication.
Other bias	Low risk	Baseline characteristics were similar between groups.