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Calcium supplements ‘raise cardiac risk by a quarter’

By Christian Duffin

NICE guidance on the prevention of osteoporosis has been challenged by researchers who have demonstrated taking calcium supplements - with or without vitamin D - raises the risk of a heart attack by 24%.

Their study – published in the British Medical Journal - adds to mounting evidence that the use of calcium supplements and vitamin D in managing osteoporosis should be re-examined.

The researchers, from New Zealand and Aberdeen, reanalysed data from the Women's Health Initiative study that assessed the use of calcium and vitamin D supplements in 36,282 women.

In a subset of 16,718 patients who had not been taking calcium supplements at the beginning of the trial, they found the women taking calcium and vitamin D supplements had up to a 22% increased risk of cardiovascular events, especially heart attacks.

When this data was added to a meta-analysis of 13 placebo-controlled trials looking at calcium supplementation, they found an increased composite risk of myocardial infarction from taking either calcium or calcium plus vitamin D of 24%. For the combined end-point of myocardial infarction or stroke, the increased risk was 15%.

Calcium supplements, along with vitamin D, are recommended in NICE guidance on osteoporosis and are commonly prescribed for other musculoskeletal conditions, as well as women on hormone replacement therapy and long-term users of corticosteroids.

Lead researcher Professor Ian Reid, professor of medicine and endocrinology at the University of Auckland, New Zealand, said that the study did not establish any differences in mortality risk among the patients compared, but added: ‘When the WHI results are taken together with the results of the other clinical trials of calcium supplements…the data justifies a reassessment of the use of calcium supplements in older people.'

Dr Alun Cooper, a GP in Sussex and clinical lead for Crawley Fracture Liaison Service, argues the research is inconclusive. He said: 'This paper is very interesting, especially following a previous meta-analysis suggesting that calcium supplements may be linked to myocardial infarction.'

'The new study does not provide any definitive evidence that there is an adverse effect of calcium and vitamin D on cardiovascular disease. Whilst there is need for further investigation there is no need for GPs to alter their current behaviour.'

Pulse reported last May on a previous meta-analysis of five randomised controlled trials that concluded that calcium increased the risk of a myocardial infarction by 31% when compared to a placebo. There was also a non-significant 20% increase in stroke risk.

Dr Claire Bowring of the National Osteoporosis Society said: 'The study highlights the need for care when considering taking calcium and vitamin D supplements. If you get all of the calcium that you need from your diet, and adequate vitamin D from exposure to sunlight, then a supplement will not be necessary.'

BMJ 2011; 342: online first 20 April

Calcium supplements 'raise cardiac risk' by a quarter


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