Calcium supplementation is effective in reducing blood pressure in various states of hypertension, including pregnancy-induced hypertension and preeclampsia. In addition, calcitropic hormones are associated with blood pressure. The hypothesis is that short-term therapy with calcium and vitamin D₃ may improve blood pressure as well as secondary hyperparathyroidism more effectively than calcium monotherapy.

The effects of 8 weeks of supplementation with vitamin D₃ (cholecalciferol) and calcium on blood pressure and biochemical measures of bone metabolism were studied. The sample consisted of 148 women (mean ± sd age, 74 ± 1 yr) with a 25-hydroxycholecalciferol (25OHD₃) level below 50 nmol/L. They received either 1200 mg calcium plus 800 IU vitamin D₃ or 1200 mg calcium/day. We measured intact PTH, 25OHD₃, 1,25-dihydroxyvitamin D₃, blood pressure, and heart rate before and after treatment.

Compared with calcium, supplementation with vitamin D₃ and calcium resulted in an increase in serum 25OHD₃ of 72% (P < 0.01), a decrease in serum PTH of 17% (P = 0.04), a decrease in systolic blood pressure (SBP) of 9.3% (P = 0.02), and a decrease in heart rate of 5.4% (P = 0.02). Sixty subjects (81%) in the vitamin D₃ and calcium group compared with 35 (47%) subjects in the calcium group showed a decrease in SBP of 5 mm Hg or more (P = 0.04). No statistically significant difference was observed in the diastolic blood pressures of the calcium-treated and calcium- plus vitamin D₃-treated groups (P = 0.10). Pearson coefficients of correlation between the change in PTH and the change in SBP were 0.49 (P < 0.01) for the vitamin D₃ plus calcium group and 0.23 (P < 0.01) for the calcium group.

A short-term supplementation with vitamin D₃ and calcium is more effective in reducing SBP than calcium alone. Inadequate vitamin D₃ and calcium intake could play a contributory role in the pathogenesis and progression of hypertension and cardiovascular disease in elderly women.