Osteoporosis is a condition characterized by the weakening of bone density.  It affects large numbers of post-menopausal women worldwide.  To combat this debilitating decline in bone health, nurses have consistently recommended supplemental calcium for their pre and post-menopausal patients.  Because post-fracture outcomes in older adults are generally poor, the maintenance of bone density via supplemental calcium has been viewed as a means of preserving overall health into later life. 

Weight-bearing exercise and increased calcium intake, both in the diet and in supplemental form, have long been mainstays of osteoporosis prevention messages.  However, as new research implicates calcium supplementation in the possible development of vascular events, these messages may be changing. 

The hormone estrogen, which drops precipitously in the years following menopause, protects the heart as well as the bones.  Therefore, normal hormonal changes automatically place post-menopausal women not only at risk for osteoporosis but also at elevated risks for vascular and cardiac events.  If supplemental calcium increases rates of vascular events in older women, the potential risks of cardio-vascular problems related to calcium must be weighed against potential bone-protecting benefits.

In order to investigate the relationship between calcium supplementation and vascular events a research team from the University of Auckland in New Zealand developed a randomized controlled trial.  They enrolled 1,471 postmenopausal women in a five-year study.  Of these participants, 732 were given 1 gram of daily calcium supplementation and 739 participants were given an alternative placebo.  The number of myocardial infarctions among the supplemental calcium group was increased by a statistically significant margin over the number experienced by placebo-taking participants.  These concerning results conflict with data collected by prior clinical trials. Previous medical literature proposed that supplemental calcium benefited the cardiovascular system by improving lipid profiles. 

While data generated by the Auckland study is not conclusive and will not change existing clinical decision-making, it should attract the attention of those who have advocated for the unmitigated use of supplemental calcium for all post-menopausal women. 

Because the Auckland study was performed as secondary research to a bone health study, it possesses certain structural flaws.  Over the course of the five year study about 500 participants, roughly divided between the supplementation and the placebo groups, dropped out for various reasons.  An additional limitation of the research is that a substantial percentage of vascular events, such as chest pain, were self-reported and subject to participants’ and family members’ memories. 

Still, certain aspects of the study are difficult to refute.  The number of myocardial infarction, stroke, or sudden death in the calcium versus the placebo group, 101 events in the calcium group as opposed to 54 for women in the placebo group, is compelling.  Also, the fact that the upward trend of vascular events steepened over time is noteworthy. 

Nurses should stay tuned as the medical community absorbs this groundbreaking study.  We may see a change in the recommendations regarding calcium supplementation in post-menopausal women in the months and years to come.

Reference

Bolland, M.J. et al. (15 January 2008). Vascular events in healthy older women receiving calcium supplementation: randomized controlled trial. British Medical Journal.

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