Calcium supplements, commonly taken by older people for osteoporosis, are associated with an increased risk of a heart attack, finds a study published online in the British Medical Journal.
The results suggest that a reassessment of the role of calcium supplements in osteoporosis management is needed.
Calcium supplements are commonly prescribed for skeletal health, but a recent trial suggested they might increase rates of heart attack (myocardial infarction) and cardiovascular events in healthy older women.
To further investigate this important issue, an international team of researchers analysed the results of 11 randomised controlled trials of calcium supplements (without co-administered vitamin D) involving 12,000 patients.
Differences in study design and quality were taken into account to minimise bias.
They found that calcium supplements were associated with about a 30% increased risk of heart attack and smaller, non-significant, increases in the risk of stroke and mortality.
The findings were consistent across trials and were independent of age, sex, and type of supplement.
Although the increase in risk is modest, the widespread use of calcium supplements means that even a small increase might translate into a large burden of disease in the population, warn the authors.
Previous studies have found no increased cardiovascular risks with higher dietary calcium intake, suggesting that the risks are restricted to supplements.
Given the modest benefits of calcium supplements on bone density and fracture prevention, a reassessment of the role of calcium supplements in osteoporosis management is warranted, they conclude.
An accompanying editorial by Professor John Cleland and colleagues suggests that, while uncertainty exists about whether the increase in heart attack and stroke is real, there are also doubts about the efficacy of calcium supplements in reducing fractures. On the basis of the limited evidence available, patients with osteoporosis should generally not be treated with calcium supplements, either alone or combined with vitamin D, unless they are also receiving an effective treatment for osteoporosis for a recognised indication. They also believe that research on whether such supplements are needed as an adjunct to effective agents is urgently required