Too Much Calcium May Be Risky

We’ve become a nation of pill takers - and many of them are supplements that we think we need, but probably don’t.  Calcium may be an example of this; it’s widely taken as a supplement to ward off osteoporosis.  A recent meta-analysis of results of studies of calcium supplementation has been published in the British Medical Journal.       

Search of the medical literature revealed 15 studies that met the criteria that were set: randomized, placebo-controlled, 500 mg or more of calcium supplement daily, 100 or more participants, average age over 40, duration more than 1 year.  There were 5 patient-level studies (i.e. data available for each patient) and 10 trial-level studies (trial data available, but without individual patient information).  Studies in which vitamin D was being taken as well were excluded.

For the patient-level studies, among a total of 8151 subjects there were 143 heart attacks in those on calcium compared with 111 on placebo, for a relative risk of 1.31 (i.e. a 31% higher risk in people taking calcium supplements).

When trial-level data were analyzed, out of 11,921 subjects there were 166 heart attacks on calcium and 130 on placebo; this yielded a relative risk of 1.27, or a 27% higher risk for those taking calcium supplements.

The authors of the study conclude that calcium supplements (without coadministration of vitamin D) are associated with an increased risk of myocardial infarction.  Although the increased risk is modest, the wide use of calcium supplements may mean “a large burden of disease in the population”.  We shall doubtless soon receive much advice from the experts on the continued use of calcium supplements compared with dietary sources, particularly in those at risk of heart disease.

Comments

[Robert Griffith]

I realize I didn't put in any advice about women taking calcium to help prevent osteoporosis - the usual thing to say is "ask your doctor"! It's a question of balancing risk - how great is your risk of osteoporosis or a fracture vs. your (slightly) increased risk of heart attack. Only your doctor can help fill in the risks on each side of the balance - it depends on your DXR or bone density test results, previous fractures, exercise level etc on the left, and general cardiovascular risk factors on the right (e.g. BP, cholesterol, exercise, overweight, family history, etc.) Hope this helps a bit.
Bob G.