Back to Cardiovascular Disease
Calcium Supplements and Cardiovascular Disease Risk
There is evidence from meta-analyses that calcium supplements are associated with an increased risk of cardiovascular disease. However, dietary calcium has not been shown to impair cardiovascular health, and the evidence related to milk products indicates that they may in fact reduce the risk of cardiovascular disease.
Introduction
Meta-analyses conducted in 2010 and 2011 indicate that the risk of cardiovascular disease is increased with intake of calcium supplements. However, this finding is still controversial, and the exact mechanisms of this relationship remain to be fully understood. Nonetheless, dietary calcium and milk products have not been associated with increased cardiovascular risk; indeed, the evidence indicates that milk products are associated with reduced risk.
For more information on milk product consumption and cardiovascular disease, consult the article on Cardiovascular Disease.
Evidence from Meta-Analyses
A 2010 meta-analysis of randomized controlled trials consisting of 11,921 participants found that calcium supplements without co-administered vitamin D increased the risk of myocardial infarction by 30%.1
No increased risk of myocardial infarction was observed in participants with dietary calcium intake below the median of 805 mg per day, with a hazard ratio of 0.98 (95% CI: 0.69-1.38, p = 0.01).
A subsequent 2011 meta-analysis was conducted to investigate the effects of personal calcium supplement use on cardiovascular risk. This meta-analysis included a re-analysis of the Women’s Health Initiative Calcium/Vitamin D Supplementation (WHI CaD) Study, which was a 7-year randomized controlled trial of calcium and vitamin D in 36,282 community dwelling post-menopausal women. The authors concluded that calcium supplements with or without vitamin D modestly increased the risk of cardiovascular events (especially myocardial infarction) by 16% in women not taking personal calcium supplements at baseline.2 Based on these findings, the authors concluded that “these data justify a reassessment of the use of calcium supplements in older people.”
In a review paper on the cardiovascular effects of calcium supplementation, Reid et al. concluded that because calcium supplements produce small reductions in fracture risk and a small increase in cardiovascular risk, there may be no net benefit from their use. However, since food sources have not been associated with adverse cardiovascular effects, they may be preferable.3
According to Osteoporosis Canada4 “It is preferable that an individual get their recommended calcium from food sources. However, if this is not possible, calcium supplements should be considered.”
Potential Mechanisms
Calcium supplement ingestion induces acute increases in serum calcium into borderline hypercalcemic range. Elevated serum calcium levels have been associated with increased carotid plaque thickness, increased likelihood of abdominal aortic calcification, increased cardiovascular risk and increased mortality.5
A potential mechanism for this relationship is that increased ionized calcium levels following ingestion lead to increased complexing of pyrophosphate, an inhibitor of tissue calcification. Thus, a decline in pyrophosphate levels leads to less inhibition of soft tissue mineralization.6
Serum calcium may also contribute to progressive vascular calcification through direct effects on vascular smooth muscle cells by binding to calcium-sensing receptors.6 Additionally, increased circulating calcium concentrations reduce levels of parathyroid hormone, a hormone that has been shown to inhibit arteriosclerotic signalling pathways in vascular smooth muscle cells.3
Furthermore, clot formation is a critical step in myocardial infarction; since calcium is essential for coagulation processes and platelet function, it is therefore possible that high levels of serum calcium induce a hypercoagulable state, which would explain early increases in the risk of myocardial infarction.3
Another mechanism by which increased serum calcium concentrations may adversely affect vascular health is through increased arterial stiffness and impaired vasodilation.3
It should be noted that calcium supplementation has also been shown to have a beneficial effect on cardiovascular health. Many studies have demonstrated that calcium supplementation has a protective effect and effectively decreases blood pressure due to the role of calcium in controlling vascular smooth muscle contractibility. Calcium may also reduce cardiovascular disease risk by binding to and increasing the excretion of bile acids and fatty acids, thereby decreasing fat absorption and consequently blood cholesterol levels. In fact, calcium supplementation has been shown to increase HDL levels and decrease LDL levels. However, a distinction has not been made as to whether the benefits are derived from dietary or non-dietary calcium supplementation.7
Nonetheless, no association has been found to date between milk products and an increased risk of cardiovascular disease. Indeed, evidence suggests that milk products may have a protective effect against heart disease and stroke.8
Conclusion
There is evidence from meta-analyses that calcium supplements may have an adverse effect on cardiovascular health; however, this does not appear to be the case for calcium obtained from foods or milk products per se. More research on the effect of calcium supplements on vascular health is needed to provide more definite answers.
Further studies on different population groups to adequately evaluate any possible risk that calcium supplements may have on cardiovascular events are also required, as are studies to clarify the mechanisms by which calcium supplements impact cardiovascular health.
References
- Bolland MJ et al. Effect of calcium supplements on risk of myocardial infarction and cardiovascular events: meta-analysis. BMJ 2010;341:c3691.
- Bolland MJ et al. Calcium supplements with or without vitamin D and risk of cardiovascular events: reanalysis of the Women's Health Initiative limited access dataset and meta-analysis. BMJ 2011;342:d2040.
- Reid IR et al. Cardiovascular effects of calcium supplementation. Osteoporos Int 2011;22(6):1649-58.
- How to choose a supplement [On-line]. Toronto (ON): Osteoporosis Canada; 2011 [cited 2011 Nov 17]. Available from: http://www.osteoporosis.ca/index.php/ci_id/5534/la_id/1.htm.
- Reid IR et al. Calcium supplementation: balancing the cardiovascular risks. Maturitas 2011;69(4):289-95.
- Reid IR et al. Does calcium supplementation increase cardiovascular risk? Clin Endocrinol (Oxf) 2010;73(6):689-95.
- Guessous I et al. Calcium, vitamin D and cardiovascular disease. Kidney Blood Press Res 2011;34(6):404-417.
- Elwood PC et al. The survival advantage of milk and dairy consumption: an overview of evidence from cohort studies of vascular diseases, diabetes and cancer. J Am Coll Nutr 2008;27(6):723S-734S.
Keywords: calcium supplements, cardiovascular disease
Scientific Evidence Keywords
Related Articles
-
Cardiovascular Disease
The evidence to date does not support an association between milk product consumption and an increased risk of cardiovascular disease.
Continue reading -
Calcium Requirements
In 2010, the Institute of Medicine (IOM) published new Dietary References Intakes for calcium. These recommendations are based on an analysis of more than 1000 studies and reports and were established to allow the majority of people to achieve and maintain good bone health.
Continue reading -
Vitamin D and Cardiovascular Disease
A systematic review of the evidence performed in 2009 for the Institute of Medicine by the Tufts Evidence-based Practice Center in preparation for revisions to the Dietary Reference Intakes for vitamin D and calcium concluded the following regarding vitamin D and cardiovascular disease:...
Continue reading
