Effects of oral calcium carbonate on blood pressure in subjects with mildly elevated arterial pressure.

Recent investigations suggest that calcium supplementation may cause a lower arterial pressure in hypertensive individuals. We studied 32 patients with mildly elevated arterial pressure (diastolic pressure 88-95 mmHg) and inadequate dietary calcium intake (less than 750 mm/day), who were randomly assigned to placebo or 1500 mg/day elemental calcium for 4 weeks. Baseline and post-treatment urinary calcium concentrations and 3 biweekly supine blood pressures were recorded. Supine systolic blood pressure in the calcium group rose during the first 2 weeks of treatment (delta systolic blood pressure +5.9 mmHg; P less than 0.025) compared with no change in supine blood pressure for the placebo group. Within the calcium group, seven out of 15 patients had decreased or unchanged supine blood pressure during treatment. A lower urinary calcium concentration and a lower dietary sodium intake were found in this subgroup compared with those whose supine blood pressure increased with calcium administration.