Dietary calcium and blood pressure: a meta-analysis of randomized clinical trials

Purpose: To assess the effect of dietary calcium supple-mentation on blood pressure. Data Sources: Published reports of trials studying the effect of dietary calcium supplementation on blood pres-sure were identified by a search of previous reviews, a MEDLINE search, a manual review of journal articles, and a review of abstracts from scientific meetings. Study Selection: Randomized clinical trials in which di-etary calcium intake varied by intervention group were selected. Multifactorial trials were not included. Data Synthesis: Data from 28 active treatment arms or strata from 22 randomized clinical trials were pooled using a weighted average method, with weights proportional to the inverse of the variance of the treatment effect. The total sample comprised 1231 persons. Because trials of both normotensive and hypertensive persons were in-cluded, subgroup analyses could be done. Pooled esti-mates of the effect of calcium supplementation on blood pressure were-0.18 mm Hg for diastolic blood pressure (95 % CI,-0.75 to 0.40 mm Hg) and-0.89 mm Hg for systolic blood pressure (CI,-1.74 to-0.05 mm Hg). Pooled estimates for systolic blood pressure were-0.53 mm Hg (CI,-1.56 to 0.49 mm Hg) for trials of normotensive per-sons and-1.68 mm Hg (CI,-3.18 to-0.18 mm Hg) for trials of hypertensive persons. Diastolic blood pressure was not significantly affected in either subgroup. Conclusion: The pooled estimate shows a statistically sig-nificant decrease of systolic blood pressure with calcium supplementation, both for hypertensive persons and for the overall sample. However, the effect is too small to support the use of calcium supplementation for prevent-ing or treating hypertension. Hypertension, one of the major risk factors for the development of cardiovascular disease, is a highly prevalent condition that affects more than 5