A recent study published last week in the British Medical Journal by Bollard et al. suggests that calcium supplementation with or without vitamin D increases the risk of cardiovascular events.  Upon re-evaluation of data from the Women’s Health Initiative Calcium/vitamin D Supplementation Study (WHI CaD), a large clinical trial, women administered calcium supplements were shown to have increased risk for myocardial infarction or stroke.  When data from the WHI CaD were combined with data from two other clinical trials, risk of myocardial infarction or stroke was increased 16% in women taking calcium supplements.

Initially, data from the aforementioned analysis is alarming and may prompt women with or at risk of osteoporosis to discontinue calcium supplementation.  However, it should be noted that certain limitations within the Bolland et al. study should be considered prior to discontinuing the use of calcium supplements.

First, analysis of the WHI CaD trial demonstrate that only women not taking calcium supplements at commencement of the study had an increased risk of cardiovascular events.  That is, women already utilizing daily calcium supplements were not at risk for myocardial infarction or stroke.  Second, because only women not taking calcium supplements at the time of study initiation were analyzed further and women previously consuming calcium supplements were excluded from the analysis, an imbalance in confounders between the calcium supplemented group and placebo group may have favored higher levels of risk factors that predisposed the calcium supplemented group to cardiovascular events.

In an editorial that was published alongside the present study, Abrahamsen et al. discusses the fact that numerous studies demonstrate cardiovascular safety and improved survival when calcium supplements are used as accessory therapies to pharmaceutical interventions, such as bisphosphonates, for the treatment of osteoporosis.

Altogether, data from the Bolland et al. study is interesting and warrants further investigation.  However, due to study limitations, conclusions regarding an association between calcium supplementation and cardiovascular events cannot be drawn.  Nonetheless, it is extremely important that individuals utilizing calcium supplements follow product monographs in terms of daily dosing and not subscribe to the notion that more is better.

Christopher P.F. Marinangeli, PhD, RD/ Scientific and Regulatory Associate at Dicentra Inc.

References

Bolland 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. Vol. 342.

Abrahamsen et al. Do calcium plus vitamin D supplements increase cardiovascular risk?: In sufficient evidence is available to support or refute the association. BMJ. 2011. Vol. 342.