Bolland and associates have recently reported on a re-analysis of the Women’s Health Initiative (WHI) observational study on calcium and vitamin D supplementation. The WHI study showed no cardiovascular risk associated with such supplementation . They differentiated the treatment arm of the WHI study into women naïve to calcium and vitamin D supplementation and women using supplementation, prior to the start of the study. In those naïve to supplementation, they found an increased risk of cardiovascular events when compared to placebo (the hazard ratios for cardiovascular events with calcium and vitamin D ranged from 1.13 to 1.22 ([i]p[/i] = 0.05 for clinical myocardial infarction or stroke, [i]p[/i] = 0.04 for clinical myocardial infarction or revascularization)). No change in cardiovascular risk was evident in patients on supplementation prior to study start.
The results for the calcium-naïve patients were included in meta-analyses of placebo-controlled trials of calcium or calcium + vitamin D supplementation. Complete trial-level data were available for 28, 072 participants from eight trials. In total, 1384 individuals had an incident myocardial infarction or stroke. Calcium or calcium + vitamin D increased the risk of myocardial infarction (relative risk (RR) 1.24, 95% confidence interval (CI) 1.07–1.45, [i]p[/i] = 0.004) and the composite of myocardial infarction or stroke (RR 1.15, 95% CI 1.03–1.27, [i]p[/i] = 0.009). The authors concluded that calcium supplements with or without vitamin D modestly increase the risk of cardiovascular events, especially myocardial infarction, a finding obscured in the WHI study by the widespread use of personal calcium supplements. A reassessment of the role of calcium supplements in osteoporosis management is advocated.
Tobie J de Villiers
Panorama MediClinic and Department of Obstetrics & Gynecology, University of Stellenbosch, Cape Town, South Africa
Bolland MJ, Grey A, Avenell A, Gamble GD, Reid IR. Calcium supplements with or without vitamin D and risk of cardiovascular events: reanalysis of the Womens Health Initiative limited access dataset and meta-analysis. BMJ 2011 Apr 19;342:d2040.
Bolland MJ, Barber PA, Doughty RN, Mason B, Horne A, Ames R, et al. Vascular events in healthy older women receiving calcium supplementation: randomised controlled trial. BMJ 2008;336:262-6.
Bolland MJ, Avenell A, Baron JA, et al. Effect of calcium supplements on risk of myocardial infarction and cardiovascular events: meta-analysis. BMJ 2010;341:c3691.
Institute of Medicine of the National Academies. Press release, 11/30/2010