Calcium is one of the most common and abundant minerals in the body and has many critical biologic functions. The body tightly controls circulating levels of calcium, usually maintaining a constant range of 1.0 to 1.2 mmol/L. Increasing calcium intake has been recommended by many healthcare professionals because of its proposed benefit for bone health.
Calcium supplements have been widely used by older men and women. 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 significantly associated with an increased risk of cardiovascular disease (CVD) and coronary heart disease (CHD).
In a meta-analysis, dietary calcium intake of 700–1000 mg per day or supplementary calcium intake of 1000 mg per day significantly increased the risk of CVD and CHD. They found that calcium supplements increased the risk of CVD by about 15% in healthy postmenopausal women. There was no significant association between using calcium supplements and the risk of cerebrovascular disease.
In the meta-analysis of calcium monotherapy, 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.
In another study, researchers concluded that calcium intake from dietary sources does not adequately increase the risk of cardiovascular disease, including coronary heart disease and stroke. In contrast, calcium supplements might raise coronary heart disease risk, especially myocardial infarction. Also, a dose-response analysis revealed that for each 300 mg/day increase in dietary calcium intake, the risk of metabolic syndrome decreased by 7%. In conclusion, these findings suggest that dietary calcium intake may be inversely associated with the risk of metabolic syndrome. 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. also, elevated calcium concentrations after calcium supplementation may increase vascular calcification, which is considered as an established factor for CVD.
Recently published data suggest 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 urgent. From a cardiovascular perspective, dietary calcium intake by eating foods high in calcium appears safe.