Although dietary calcium intake may confer some cardiovascular benefits calcium supplements appear to raise the risk of myocardial infarction (MI), a recent study published in Heart, has found.

This was a prospective study to evaluate the association of dietary calcium intake and calcium supplementation with risk of MI, stroke and overall cardiovascular mortality. The trial used data from the Heidelberg cohort of the European Prospective Investigation into Cancer and Nutrition (EPIC) study. This cohort comprised 23,980 patients aged 35–64 years who had had no major cardiovascular events at recruitment. Multivariate Cox regression models were used to estimate hazard ratios (HR).

There were 354 MIs, 260 strokes and 267 cardiovascular deaths during the 11 year follow-up period. Compared with the lowest quartile, the third quartile of total dietary and dairy calcium intake had a significantly reduced MI risk, HR 0.69 (95% CI: 0.50-0.94) and HR 0.68 (95% CI: 0.50-0.93) respectively. There were no significant differences seen for stroke risk and CVD mortality.

However, the findings for calcium supplements were quite different. Those taking calcium supplements had a significantly increased MI risk compared with those who had never taken supplements, HR 1.86 (95% CI: 1.17-2.96). This became even more pronounced for those who took only calcium and no other type of supplement, HR 2.39 (95% CI: 1.12-5.12).

The debate concerning calcium and cardiovascular risk is ongoing and this study suggests that the form in which calcium is ingested may be a key factor in the resultant cardiovascular effects.

Although calcium intake from diet might confer some cardiovascular benefits calcium supplements appear to raise MI risk and the authors conclude that such supplements should be taken with caution. One can postulate that the higher plasma concentration from bolus dosing increases the likelihood of harm compared with the lower levels seen with dietary intake and this is mirrored in the effect on renal calculi. Furthermore, there is only a small benefit on fracture reduction and this is when calcium supplements are given in combination with vitamin D.

Therefore evidence such as this continues to question our use of such supplements in patients perceived to be at risk of fracture.

Dr Peter Savill