Methods | Randomised, double‐blind, placebo‐controlled trial. The trial was conducted in the United States of America. |
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Participants | Normotensive male participants. Ethnicity: Black (n = 21) and white (n = 54)." Age: 19 to 52 years. |
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Interventions | Internvention group: calcium, 1500 mg a day. Control group: placebo. "Participants were randomly assigned within racial groups to either a treatment". Trial duration: 12‐week period. |
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Outcomes | Blood pressure Serum levels of total and ionised calcium Total inorganic phosphorus Parathyroid hormone Overnight urinary electrolyte values |
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Notes | ||
Risk of bias | ||
Bias | Authors' judgement | Support for judgement |
Random sequence generation (selection bias) | Unclear risk | Not described |
Allocation concealment (selection bias) | Low risk | The supplements were strip‐wrapped individually and coded by someone not involved in the research study. The participants did not know which group they were assigned to, and the researcher(s) who collected other information also were not aware of the group assignment. Early analyses were completed prior to revealing the assigned groups as well. |
Blinding of participants and personnel (performance bias) All outcomes | Low risk | Assignment was double‐blind. "Indistinguishable placebo tablets were composed of microcrystalline methylcellulose and starch." |
Blinding of outcome assessment (detection bias) All outcomes | Low risk | "Use of a random‐baseline sphygmomanometer and blinded observers to eliminate bias during blood pressure measurement, documentation of nutrient intake other than the supplement, and control for body weight and other possible confounders." |
Incomplete outcome data (attrition bias) All outcomes | Low risk | All participants randomised were included in the results. |
Selective reporting (reporting bias) | Low risk | All outcomes were reported. |
Other bias | Low risk | The groups were similar at baseline. |