Does baseline serum total calcium level influence the blood pressure response to calcium supplementation? A double-blind study

Abstract

This was a randomized and double-blind study to examine: (1) the effect of a 1500 mg/day calcium supplement vs a placebo for 8 wk in 42 adults with high normal or mildly elevated blood pressure (BP) and, (2) the relationship between baseline serum total calcium levels and BP response to calcium supplementation. Following the experimental protocol, mean pressures were lower in the treatment vs placebo group (95.7 mmHg and 102.1 mmHg, p = 0.002), but response was not related to initial serum total calcium levels. After 8 wk of calcium supplementation, serum total calcium was greater in the treatment group compared to the placebo group (p = 0.02). Within the treatment group only, the change in total serum calcium was related to the change in parathyroid hormone (r = -0.92, p = 0.0002); and the change in ionized calcium was related to the change in parathyroid hormone (r = -0.68, p = 0.03) in the subgroup with low baseline serum total calcium. This study provides further support for the hypotensive effect of supplemental calcium in some people. However, it fails to clarify or expand upon previous reports that a low serum total calcium level might be predictive of the blood pressure response to increased calcium.