Dawson‐Hughes 1997.

Methods	Boston STOP IT (Sites Testing Osteoporosis Prevention Intervention Treatment). Randomised, double‐blind, placebo controlled trial using parallel group design (two intervention groups).
Participants	Country: United States. Number of participants randomised: 389, healthy, ambulatory participants (55% women), aged 65 years or older (mean 71). Inclusion criteria: healthy, ambulatory men and women 65 years of age or older. Exclusion criteria: current cancer or hyperparathyroidism; a kidney stone in the past five years; renal disease; bilateral hip surgery; therapy with a bisphosphonate, calcitonin, oestrogen, tamoxifen, or testosterone in the past six months or fluoride in the past two years; femoral‐neck bone mineral density more than 2 SD below the mean for participants of the same age and sex; dietary calcium intake exceeding 1500 mg per day; and laboratory evidence of kidney or liver disease.
Interventions	Participants were randomly assigned to receive: Intervention group 1: vitamin D3 (700 IU) plus calcium (500 mg) daily (n = 187); Intervention group 2 (Control group): matched placebo tablets daily (n = 202); for a three‐year period. Calcium was in the form of calcium citrate malate. Placebo pills contained microcrystalline cellulose.
Outcomes	The primary outcome measures were bone mineral density, biochemical measures of bone metabolism, and the incidence of nonvertebral fractures.
Stated aim of study	"To examine the effects of combined vitamin D supplementation and calcium on bone loss, biochemical measures of bone metabolism, and the incidence of nonvertebral fractures in men and women 65 years of age or older who were living in the community."
Notes	Procter & Gamble, Cincinnati manufactured calcium tablets. Additional information on mortality was received through personal communication with Professor Bess Dawson‐Hughes (04.02.2009).
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Sequence generation was achieved using computer random number generation.
Allocation concealment (selection bias)	Low risk	Allocation was controlled by a central and independent randomisation unit so that intervention allocations could not have been foreseen in advance of, or during, enrolment.
Blinding (performance bias and detection bias) All outcomes	Low risk	The trial was described as blinded, the parties that were blinded, and the method of blinding was described, so that knowledge of allocation was adequately prevented during the trial.
Incomplete outcome data (attrition bias) All outcomes	Low risk	The numbers and reasons for dropouts and withdrawals in all intervention groups were described.
Selective reporting (reporting bias)	Low risk	Pre‐defined or clinically relevant and reasonably expected outcomes are reported on.
Industry bias	Unclear risk	Procter & Gamble, Cincinnati manufactured calcium tablets.
Other bias	Low risk	The trial appears to be free of other components that could put it at risk of bias.