Objective: To test the effect of daily supplemental calcium on serum total and high-density lipoprotein cholesterol (HDL-C) levels and blood pressure in adults.
Design: Randomized, double-blind, placebo-controlled clinical trial; adjunct study to a trial of calcium and colon cell proliferation in patients with sporadic adenoma.
Setting: Outpatient clinic.
Patients: A total of 193 men and women, aged 30 to 74 years.
Intervention: Treatment with 1.0 and 2.0 g/d of elemental calcium vs placebo over a 4-month period for cholesterol determinations and 6 months for blood pressure.
Main outcome measures: Serum total cholesterol and HDL-C levels, systolic and diastolic blood pressure.
Results: Because there were no apparent differences in responses between the 1.0-g and 2.0-g calcium groups, their data were combined and compared with those of the placebo group. Among all participants, the mean total cholesterol level dropped 0.07 mmol/L (2.9 mg/dL) (1.3%) (P = .43) more, and the mean HDL-C level dropped 0.01 mmol/L (0.4 mg/dL) (1.1%) (P = .71) less in the calcium group than in the placebo group. Among participants without a history of hypercholesterolemia, the mean total cholesterol level dropped 0.18 mmol/L (6.8 mg/dL) (3.3%) (P = .10) and the HDL-C level dropped 0.02 mmol/L (0.6 mg/dL) (1.5%) (P = .61) more in the calcium group than in the placebo group. Among all participants, there was no apparent change in blood pressure until 6 months, when the mean systolic blood pressure dropped 0.8 mm Hg (0.6%) (P = .85) and the mean diastolic blood pressure dropped 0.4 mm Hg (0.5%) (P = .80) more in the calcium group than in the placebo group.
Conclusions: There were no substantial or statistically significant effects of calcium supplementation on total cholesterol or HDL-C levels or on blood pressure. There was a suggestion (not statistically significant) of a 0.07 to 0.18 mmol/L (3-7 mg/dL) or 2% to 4% drop in the total cholesterol level, a finding similar to that reported in other studies, which indicates the need for further study.