Sacks 1998.
| Study characteristics | ||
| Methods | Randomised, double‐blind parallel‐group trial The trial was conducted in the United States of America. |
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| Participants | 321 participants: 93% completed baseline and midpoint measurements. "Exclusion criteria included reported diastolic blood pressure 65 mm Hg; hypertension; BMI > 32 kg/m²; insulin‐dependent diabetes; cardiovascular disease; renal failure; medications that affect blood pressure, weight loss diets, use of nutritional supplements of calcium, magnesium, or potassium (including antacid preparations)". |
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| Interventions | Intervention group: calcium carbonate 1200 mg daily (caltrate 600 mg twice daily, Lederle Laboratories) Control group:identical placebo Trial duration: 16 weeks "The placebo group received twice the number of participants as the four treatment groups to improve statistical power". |
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| Outcomes | Ambulatory 24‐hour blood pressure 24‐hour urine Body weight Health and side effects questionnaire Pill counts |
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| Notes | Participants who had baseline systolic blood pressure above 160 mmHg or diastolic blood pressure above 95 mm Hg were excluded and advised to see their physicians. | |
| Risk of bias | ||
| Bias | Authors' judgement | Support for judgement |
| Random sequence generation (selection bias) | Low risk | The randomisation was performed by a computer program directed by the statistician on the project. The statistician had no contact with the data collectors or the participants (information provided by the author). |
| Allocation concealment (selection bias) | Unclear risk | Not described |
| Blinding of participants and personnel (performance bias) All outcomes | Low risk | Participants were under double‐blind conditions for 16 weeks but methods not described. The participants were not informed about their specific supplement group. |
| Blinding of outcome assessment (detection bias) All outcomes | Low risk | The blood pressure machine automatically entered the blood pressure data on computer tape that was later converted to an ASCII file at the study office. |
| Incomplete outcome data (attrition bias) All outcomes | Unclear risk | 321 participants were randomised. 300 participants were available for follow‐up measurements and 290 completed the study measurements. |
| Selective reporting (reporting bias) | Low risk | Primary outcome reported |
| Other bias | Low risk | Baseline characteristics were similar. |