Abstract
BackgroundConsiderable controversy exists regarding the association between dietary calcium intake and risk of mortality from cardiovascular disease and all causes. Therefore, we performed a meta-analysis of prospective cohort studies to examine the controversy.MethodsWe identified relevant studies by searching MEDLINE, Embase, and the Cochrane Library databases between 1 September 2013 and 30 December 2013. Reference lists of relevant articles were also reviewed. Observational prospective studies that reported relative risks and 95% confidence intervals for the association of calcium intake with cardiovascular and all-cause mortality were eligible. Study-specific relative risks were pooled using a random-effects model.ResultsIn this meta-analysis, 11 prospective studies with 12 independent cohorts, involving 757,304 participants, were eligible. There was evidence of a non-linear association between dietary calcium intake and risk of mortality from cardiovascular disease (P for non-linearity <0.01) and all causes (P for non-linearity <0.01). A dose-response analysis showed a U-shaped relationship between dietary calcium intake and cardiovascular mortality. Intakes that were lower and higher than around 800 mg/day were gradually associated with a higher risk of cardiovascular mortality. For all-cause mortality, we also observed a threshold effect at intakes around 900 mg/day. The risk of all-cause mortality did not decrease further at intakes above 900 mg/day.ConclusionsThis meta-analysis of prospective cohort studies suggests that dietary calcium intake is associated with cardiovascular mortality in a U-shaped manner and that high dietary calcium intake (>900 mg/day) is not associated with a decreased risk of all-cause mortality.Electronic supplementary materialThe online version of this article (doi:10.1186/s12916-014-0158-6) contains supplementary material, which is available to authorized users.
Highlights
Considerable controversy exists regarding the association between dietary calcium intake and risk of mortality from cardiovascular disease and all causes
Our results indicated that intakes of about 800 mg/day, which corresponds to the recommended daily intake for Swedish women aged more than 50 years [38], conferred the lowest risk of cardiovascular mortality
The present study found no evidence that calcium supplements increased the risk of cardiovascular mortality
Summary
Considerable controversy exists regarding the association between dietary calcium intake and risk of mortality from cardiovascular disease and all causes. Some prospective studies found an inverse association between dietary calcium intake and mortality from ischemic heart disease or cardiovascular disease (CVD) [4,5]. Several recent re-analyses of randomized trials showed that calcium supplements are associated with a higher risk of both ischemic heart disease and stroke, which are two major causes of cardiovascular mortality [6,7,8]. The current evidence for an association between calcium intake and risk of cardiovascular and all-cause mortality remains insufficient and controversial. Differences in calcium intake doses, which were higher in the trials, may have led to the differences between the observational studies and randomized trials
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