Thursday, March 13, 2014

Calcium: Is it a Cardiovascular Risk?

As a chiropractic physician specializing in osteopenia and osteoporosis, being questioned by my patients about the safety of calcium was something I never would have foreseen. For years, in addition to recommending various dietary, supplemental and life-style changes to improve bone health and reduce fracture risk, I have recommended that patients take in a total of 1,000 to 1,200 mg/day of calcium from dietary and supplemental sources. Then, in 2008, a study by Bolland et al. (2008) reported the possible association between calcium supplementation and cardiovascular risk1 and my job got a little more difficult. This study (and two subsequent studies: Bolland et al. (2010) and Li, et al. (2012) that supported Bolland’s initial findings2,3) hit the newsstands and literally struck fear in hearts of many osteoporosis patients. According to Bolland, et al. (2010) “Calcium supplements (without coadministered vitamin D) are associated with an increased risk of myocardial infarction.” “A reassessment of the role of calcium supplements in the management of osteoporosis is warranted.”
 
Comments from some of my patients such as “Doc, what are you trying to do, kill me?...I’m not taking that calcium!” soon followed the media blitz. (That’s a slight exaggeration, but you get the gist.) As a chiropractor working to improve his patients’ skeletal health mainly through natural means, and one who understands the importance of calcium and vitamin D for bone health, this type of response could impede optimal care. It is true, calcium isn’t everything when it comes to bone health…but it is important.

Thankfully, there has now been time to evaluate these studies and new research has countered their conclusions. For example, Abrahamsen, et al. (2011) and Nordin, et al. (2011) have criticized Bolland’s research pointing out design flaws in the study and questioning how the cardiovascular events themselves were determined.4,5 Research by Samelson, et al. (2012) found no support to conclude that high calcium intake increases coronary artery calcification and that there is not sufficient evidence regarding vascular calcification risk to modify current recommendations for calcium intake to protect skeletal health.6 Heaney, et al. (2012) from Creighton University Medical Center reviewed data from 2 epidemiological studies, a meta-analysis of controlled clinical trails and other cohort studies and found that “little evidence exists for plausible biological mechanisms to link calcium supplement use with adverse cardiovascular outcomes.”7 And, in an effort to determine the exact physiological mechanism, if any, that could explain the connection between acute rises in blood calcium (as seen with supplemental calcium intake) and heart attacks, Burt et al. (2013) studied the effects of giving 25 subjects 1,000 mg oral calcium citrate. They then evaluated changes in blood markers and specific cardiovascular function parameters linked to cardiovascular risk. The authors concluded that further research was needed but that “the rise in serum calcium following supplement administration does not acutely exert an adverse effect on these parameters of cardiovascular function.”8

As a member of the American Society for Bone and Mineral Research, I recently attended our 2013 Annual Meeting in Baltimore, MD (October 4 – 7) and was fortunate to attend talks by the lead authors of two important new studies that evaluated cardiovascular risk and calcium intake. The first presentation was by Dr. Douglas Bauer, MD, from the University of California, San Francisco. Dr. Bauer’s observational trial assessed calcium intake (both dietary and supplemental) and mortality in 5967 men over the age of 65 years in the Osteoporotic Fractures in Men (MrOS) study. The participants’ intake of calcium was 1142 ± 590 mg/day and 65% used calcium supplements. Over a 10-year follow-up period, those who took in more than 1565 mg/day of calcium had lower mortality than those who took in less than 621 mg/day. The highest mortality from cardiovascular disease was seen in those with the lowest calcium intake (less than 621 mg/day). The authors concluded there was “no evidence that supplements increased the risk of mortality among those with the highest dietary calcium intake (interaction p value = 0.84).” And, “total calcium intake, use of calcium supplements and the combination of high dietary calcium intake and supplement use were not associated with total or cardiovascular mortality.”9

In the second presentation, Dr. Joshua Lewis, MD, PhD, from the University of Western Australia, Perth, reported on his meta-analysis of 19 randomized controlled trials that studied women over the age of 50 who took calcium supplements. The analysis encompassed 59,844 participants. The authors concluded “data from this meta-analysis does not support the concept that calcium supplementation with or without vitamin D increase the risk of ischemic heart disease or total mortality in elderly women.”10

Hopefully the Bauer and Lewis studies will help reduce patient fears concerning supplemental calcium and heart disease. That said, I do believe that when supplementing a patient with calcium it is important to maintain optimal vitamin D levels and encourage adequate intake of vitamin K, magnesium, and trace minerals. Vitamins and minerals work synergistically, and to flood the body with calcium without the necessary utilizing factors has the potential to cause metabolic imbalance. 

1  Bolland M.J., P.A. Barber, R.N. Doughty, et al. 2008. Vascular events in healthy older women receiving calcium supplementation: randomized controlled trial. BMJ 336(7638):262-6.
2  Bolland M.J., A Avenell, J.A. Baron, et  al. 2010. Effect of calcium supplements on risk of myocardial infarction and cardiovascular events: meta-analysis. BMJ 341:c3691.
3  Li K., R. Kaaks, J. Linseisen, and S. Rohrmann. 2011. Associations of dietary calcium intake and calcium supplementation with myocardial infarction and stroke risk and overall cardiovascular mortality in the Heidelberg cohort of the European Prospective Investigation into Cancer and Nutrition study (EPIC-Heidelberg). Heart 98(12):920-5.
4  Abrahamsen B. 2011. Editorial: Do calcium plus vitamin D supplements increase cardiovascular risk? BMJ 343:d2080.
5  Nordin B.E., J.R. Lewis, R.M. Daly, et al. 2011. The calcium scare—What would Austin Bradford Hill have thought? Osteoporos Int 22(12):3073-7.
6  Samelson E.J., S.L. Booth, C.S. Fox, et al. 2012. Calcium intake is not associated with increased coronary artery calcification: the Framingham Study. Am J Clin Nutr 96(6):1274-80.
7  Heaney, R.P., S. Kopecky, K.C. Makl, et al. 2012. A review of calcium supplements and cardiovascular disease risk. Adv Nutr 3(6):763-71.
8  Burt M.G., B.L. Mangelsdorf, D. Srivastava, C.J. Petersons. 2013. Acute effect of calcium citrate on serum calcium and cardiovascular function. J Bone Miner Res 28(2):412-8.
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