Dietary calcium improves bone mineral density (BMD) and lowers blood pressure (BP) in spontaneously hypertensive rats (SHR)

An increase in calcium intake has been proposed as a non-pharmacological treatment of high BP. Moreover, an inverse relationship has been observed between bone mineral content and BP. We therefore postulated that dietary Ca²⁺ improves Ca²⁺ homeostasis, restoring BMD and BP to normal, and measured BP (mmHg), BMD (mg/area), calcitriol (D, pg/ml), PTH (pg/ml), ionized Ca²⁺ (iCa, mM) and CaBP-9K (μg/mg, a marker of intestinal Ca²⁺ transport) in SHR fed 0.1%, 0.2%, 1.0% or 2.0% Ca²⁺ diets for 6 weeks (n=16/group, half SHR provided by Taconic (T), and half by Chartes River (CR). Results were: (*, p<0.05, ANOVA) m±SEM 0.1% Ca 0.2% Ca 1.0% Ca 2.0% Ca BP* 212.6±4.0 211.9±3.8 200.1±3.8 176.6±4.7 iCa * 1.26±0.02 1.33±0.01 1.35±0.01 1.34±0.01 D * 503.5±7.0 182.2±8.2 92.9±4.7 96.2±3.3 CaBP * 34.6±1.7 28.1±1.5 20.4±1.1 17.4±1.1 BMD * 89±2 108±2 133±2 135±2 PTH T * 211.5±25.8 164.9±21.8 106.9±10.2 83.4±11.4 CR 134.0±46.0 118.6±24.2 159.7±20.1 105.1±12.5 The following correlations were found: iCa/D (P<0.0001, r=-0.54); iCa/PTH (p<0.0002, r=-0.48), BMD/D (p<0.0001, r=-0.84), BMD/BP (p<0.0006, r=-0.47), BMD/CABP (p<0.0001, r=-0.75), and D/CaBP (p<0.0001, r=0.70). The data suggest that increased calcium intake improves calcium homeostasis as well as systemic BP and BMD, thus supporting the hypothesis that essential hypertension can be successfully treated with adequate Ca²⁺ intake.