Effect of calcium supplementation in an older population with mildly increased blood pressure

This study was undertaken to determine if calcium carbonate supplementation could reduce blood pressure in an older population that had mildly increased pressure and if blood pressure reduction could be maintained over the course of 1 year with continued supplementation. Volunteers 50 to 80 years of age were included if their systolic blood pressure (when not taking antihypertensive medication) was consistently ≥ 140 mm Hg or if diastolic blood pressure was ^ 90 mm Hg during a 4-week baseline period. Each subject then received placebo tablets for 4 weeks followed by 1 g calcium carbonate tablets for 12 weeks in a single-blinded fashion. If either systolic or diastolic blood pressure was reduced by at least 5 mm Hg with calcium supplementation as compared to placebo, calcium supplementation was continued for 36 weeks. A 25% subsample of subjects completed a 12-week placebo run-out. Supine and standing systolic and diastolic blood pressure did not change significantly with 12 weeks of calcium carbonate as compared to placebo (P = NS). In 42 of 103 subjects with at least a 5 mm Hg initial decrease in blood pressure who were continued on calcium supplementation, blood pressure did not change significantly through 36 weeks. In the 12 subjects who completed the placebo runout period, systolic pressures increased significantly (P <05) and did not differ from baseline (P = NS). There is no evidence in this study for general use of calcium supplementation to reduce blood pressure in an older population. Although the conclusions are limited by this study design, individuals who manifest blood pressure reduction with calcium supplementation may sustain this response for at least 1 year. Am J Hypertens 1992;5:230-237.