[Effects of oral calcium supplementation on blood pressure in population]

To assess the effects of oral intake of calcium lactate tablet on blood pressure and serum levels of sodium, potassium, calcium and phosphors.

In a rural area with natural population with higher average blood pressure and prevalence of hypertension, and with high salt and low calcium intake in diet in Yu County, Shanxi Province, 112 volunteers aged 30 to 64 years were selected based on a mass screening for hypertension, and randomized into trial and control groups with double blinding, taking calcium lactate tablets (800 mg of calcium daily) and placebo respectively for five weeks. Ninety-eight of them complied with the medical order completely, 39 males and 59 females, and were followed-up for systolic (SBP) and diastolic blood pressure (DBP), and their fasting venous blood specimen and 8-hour nocturnal urine specimens were collected. Twenty-four-hour diet recall was obtained for three consecutive days from all of them.

Reduction of 4.7 mm Hg (0.62 kPa) and 2.7 mm Hg (0.36 kPa) in systolic and diastolic blood pressure, respectively in the trial group was observed, as compared with that in control one, with P-values of 0.027 and 0.074, respectively, after 35 days of treatment. The higher their baseline BP level, the greater reduction of their BP after treatment. Urinary excretion of calcium increased and serum level of phosphorus reduced after oral administration of calcium.

In an area with higher prevalence of hypertension and with high salt and low calcium intake in diet, change in diet composition or supplementation with calcium could reduce their average blood pressure and prevent them from hypertension for those with mild and moderate hypertension and in high risk with higher blood pressure.