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from Eastwood Group Practice

A recent study in the British Medical Journal hit the headlines in July 2010, linking calcium supplements with an increased risk of heart disease. Is this a real link and what should you do if you are taking calcium tablets for prevention of fractures?

The study by Bolland included 12,000 patients in a Cochrane Systematic Review, a robust method of collating the results of lots of small studies enabling small differences to be significantly identified. In their study they demonstrated that taking calcium supplements alone produced a 30% relative increase in myocardial infarction. The study itself excluded patients taking calcium with vitamin D - the most common formulation of calcium supplementation. Interestingly the study did not identify an increase in mortality associated with the increased number of myocardial infarctions. Is this because calcium causes other symptoms (such as indigestion) leading to further investigations by the GP and subsequent discovery of ischaemic heart disease? 

Does extra calcium matter? In theory yes. The deposition of calcium in tissues other than bone has been shown in patients with problems processing calcium, such as patients with renal failure. In these patients there is known to be an increased risk of cardiovascular events. Calcium forms an integral component of the 'arterial plaque' involved in the developement of atherosclerosis - the underlying pathological process leading to myocardial infarction. However calcium alone may not be the answer. A wide number of other vitamins are known to be important in the processing of calcium such as vitamin K, and it may be that individuals with low vitamin K levels are more likely to develop problems as the calcium does not mineralise the bone, but deposits other tissues. 

So where does this leave us? There is certainly a question raised about the use of calcium supplements without vitamin D in patients at risk of cardiovascular disease. Perhaps more importantly the use of calcium supplementation as a cheap effective and safe method of preventing fractures should be reviewed. There is significant evidence that the calcium increases the mineralization of the bone, but there is very little evidence that it reduces the risk of fractures. Indeed with the high mortality associated with hip fractures, the lack of any reduction further highlights the poor evidence base for calcium supplementation. At present the NICE guidance for osteoporosis (a thesis in itself), suggests the use of calcium and vitamin D in conjunction with a bisphosphonate such as alendronic acid. This may change.