Calcium Intake and Cardiovascular Disease Risk: An Updated Systematic Review and Meta-analysis.

BACKGROUND: Conflicting evidence exists regarding potential cardiovascular risks associated with high levels of calcium intake. PURPOSE: To update and reanalyze 2 systematic reviews to examine the effects of calcium intake on cardiovascular disease (CVD) among generally healthy adults. DATA SOURCES: MEDLINE; Cochrane Central Register of Controlled Trials; Scopus, including EMBASE; and previous evidence reports from English-language publications from 1966 to July 2016. STUDY SELECTION: Randomized trials and prospective cohort and nested case-control studies with data on dietary or supplemental intake of calcium, with or without vitamin D, and cardiovascular outcomes. DATA EXTRACTION: Study characteristics and results extracted by 1 reviewer were confirmed by a second reviewer. Two raters independently assessed risk of bias. DATA SYNTHESIS: Overall risk of bias was low for the 4 randomized trials (in 10 publications) and moderate for the 27 observational studies included. The trials did not find statistically significant differences in risk for CVD events or mortality between groups receiving supplements of calcium or calcium plus vitamin D and those receiving placebo. Cohort studies showed no consistent dose-response relationships between total, dietary, or supplemental calcium intake levels and cardiovascular mortality and highly inconsistent dose-response relationships between calcium intake and risks for total stroke or stroke mortality. LIMITATIONS: CVD disease outcomes were secondary end points in all trials. Dose-response metaregression analysis of cohort studies was limited by potential confounding, ecological bias, and imprecise measures of calcium exposures. Data were scarce regarding very high calcium intake-that is, beyond recommended tolerable upper intake levels. CONCLUSION: Calcium intake within tolerable upper intake levels (2000 to 2500 mg/d) is not associated with CVD risk in generally healthy adults. PRIMARY FUNDING SOURCE: National Osteoporosis Foundation.