Calcium is one of the body's most common and plentiful minerals and has many essential biologic functions. The body tightly controls circulating calcium levels, usually maintaining a constant range of 1.0 to 1.2 mmol/L. Many medical professionals have suggested increasing calcium intake because of its proposed bone health benefits.
Older men and women have widely used calcium supplements. However, in little more than a decade, authoritative recommendations have changed from encouraging the widespread use of calcium supplements to stating that they should not be used for primary prevention of fractures. The researchers found that calcium supplements were strongly linked to increased cardiovascular disease (CVD) and coronary heart disease (CHD) risk. A 2021 review of studies showed that dietary calcium intake of between 700 to 1,000 milligrams a day or a supplementary intake of 1,000 milligrams a day significantly increased a person's risk of cardiovascular disease and coronary heart disease, which can result in heart attacks. They discovered that healthy postmenopausal women who used calcium supplements had a 15% increased risk of CVD. But the risk of cerebrovascular disease was not significantly correlated with using calcium supplements.
In the meta-analysis of calcium monotherapy (without coadministered vitamin D), there was an interaction between dietary calcium intake and the risk of myocardial infarction (MI) with calcium supplements when the cohort was divided by median dietary calcium intake. However, when the cohort was divided by quintile of dietary calcium intake, there was no interaction, and the risk of myocardial infarction (MI) with calcium was similar in the groups with the lowest and highest calcium intake.
In the meta-analysis of calcium monotherapy, there was no interaction between dietary calcium intake and the risk of stroke or the composite cardiovascular endpoint in this meta-analysis and no interaction between dietary calcium intake and cardiovascular events in the Women's Health Initiative CaD trial (WHI CaD). Therefore, the increased cardiovascular risk from calcium supplements appears to be independent of dietary calcium intake.
Researchers in another study concluded that calcium intake from dietary sources does not sufficiently increase the risk of cardiovascular disease, including coronary heart disease and stroke. In contrast, calcium supplements might increase coronary heart disease risk, especially myocardial infarction.
Additionally, a dose-response analysis showed that the risk of metabolic syndrome decreased by 7% for every 300 mg/day increase in dietary calcium consumption. According to these data, the risk of metabolic syndrome may be inversely correlated with dietary calcium consumption. The cause of the increased cardiovascular risk from calcium supplements remains unclear, but potential mechanisms have been extensively reviewed. The finding of increased cardiovascular risk from calcium supplements but not dietary calcium intake in most observational studies have led to the hypothesis that the rapid and sustained increases in serum calcium after ingestion of a calcium supplement may have a central role. Additionally, increased vascular calcification, recognized as a known risk factor for CVD, may occur due to increased calcium concentrations following calcium administration.
Recently research suggests a significant increase in incident coronary artery calcification with calcium supplementation. Along with previous data associating calcium supplementation with cardiovascular mortality and all-cause mortality, this new evidence stresses the need for an evidence-based approach to calcium supplementation. Moreover, educating health care providers on the possible risk of excessive and unnecessary calcium supplementation is critical. From a cardiovascular perspective, dietary calcium intake by eating foods high in calcium appears safer than calcium loading with supplements.