Entezari 2015.

Study characteristics
Methods	Double‐blinded placebo‐controlled clinical trial
Participants	Normotensive females Age: 18 to 30 years Setting: Shahid Beheshti University of Medical Sciences in Tehran, Iran
Interventions	Intervention: four capsules of supplementary calcium daily; each capsule contained 625 mg calcium carbonate, which is equal to 250 mg of calcium element. Control: 1000 mg dextrose capsules instead of calcium carbonate Trial duration: 1 month
Outcomes	Systolic and diastolic blood pressure in supine position after 10 min of rest
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Not mentioned: "Eligible cases were randomly divided into two groups (treatment and control); treatment group received four capsules of supplementary calcium daily".
Allocation concealment (selection bias)	Unclear risk	The method was not described
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	This double‐blinded placebo‐controlled clinical trial was carried out in normotensive females.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Not mentioned
Incomplete outcome data (attrition bias) All outcomes	High risk	75 started; the authors did not mention how many in each group. More than "15 withdrew"; 22 in total (29.3%) finished "27 in calcium and 26 in control".
Selective reporting (reporting bias)	Unclear risk	No protocol available
Other bias	Low risk	This study was done in a population who were calcium deficient, and therefore the effect of calcium supplement should be shown more prominently.