29 July 2010 Last updated at 22:59 GMT
Calcium pills 'increase' risk of heart attack
By Emma Wilkinson Health reporter, BBC News
Calcium pills Calcium supplements are commonly taken by older people at risk of fracture
Calcium supplements taken by many older people could be increasing their risk of a heart attack, research shows.
The study, in the British Medical Journal, said people who took supplements were 30% more likely to have a heart attack.
Data from 11 trials also suggested the medicines were not very effective at preventing bone fractures.
Almost 3m people in the UK are thought to have osteoporosis and many take calcium pills to prevent fractures.
The study recommends doctors review their use of calcium supplements for managing osteoporosis.
The National Osteoporosis Society said most people should be able to get enough calcium through their diets, rather than reaching for the medicine cabinet.
The researchers said those who had a diet naturally high in calcium were at no increased danger.
In all 12,000 people aged over 40 took part in the trials of calcium supplements of 500mg or more a day.
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It is a balance of risks - people should consider the risks involved and how they apply to their own circumstances and discuss the matter with their GP”
End Quote Dr Alison Avenell Study author
The risk of heart attack was seen across men and women, was independent of age and the type of supplement given.
A small increased risk of death was seen in the study but was not statistically significant, the researchers said.
The reason for the increased risk of heart attack is not clear but it is thought the extra calcium circulating in the blood could lead to a hardening of the arteries.
Calcium in the diet is safe and the Food Standards Agency recommends adults have 700mg of calcium a day from milk, cheese and green, leafy vegetables.
Dr Alison Avenell, from the University of Aberdeen which did the research with colleagues in New Zealand and the US, said the evidence suggests calcium supplements only have a limited benefit in preventing fractures, especially when compared to other treatments available.
"It is a balance of risks - people should consider the risks involved and how they apply to their own circumstances and discuss the matter with their GP," she said.
She added the results did not necessarily apply to younger people with conditions for which they take calcium.
Judy O'Sullivan, senior cardiac nurse at the British Heart Foundation, said the results should be interpreted with caution because the trials did not set out to look at the risk of heart attack.
"However, the research should not be completely ignored," she said.
"Any new guidelines on the prevention of fractures in those most vulnerable to them should take this type of analysis into account."
Dr Claire Bowring, of the National Osteoporosis Society, said: "We've always recommended that people should aim to get the calcium they need from their diet to help build stronger bones.
"If you get all of the calcium that you need from your diet and adequate vitamin D from exposure to sunshine, then a supplement will not be necessary."
She said there were still questions to be answered about the treatment of osteoporosis but advised people taking calcium supplements to talk to their GP, especially if they have a heart condition.
Published 29 July 2010, doi:10.1136/bmj.c3691
Cite this as: BMJ 2010;341:c3691
Effect of calcium supplements on risk of myocardial infarction and cardiovascular events: meta-analysis
Mark J Bolland, senior research fellow1, Alison Avenell, clinical senior lecturer2, John A Baron, professor3, Andrew Grey, associate professor1, Graeme S MacLennan, senior research fellow2, Greg D Gamble, research fellow1, Ian R Reid, professor1
1 Department of Medicine, Faculty of Medical and Health Sciences, University of Auckland, Private Bag 92 019, Auckland 1142, New Zealand, 2 Health Services Research Unit, University of Aberdeen, 3 Department of Medicine, and Department of Community and Family Medicine, Dartmouth Medical School, NH, USA
Correspondence to: I R Reid email@example.com
Objective To investigate whether calcium supplements increase the risk of cardiovascular events.
Design Patient level and trial level meta-analyses.
Data sources Medline, Embase, and Cochrane Central Register of Controlled Trials (1966-March 2010), reference lists of meta-analyses of calcium supplements, and two clinical trial registries. Initial searches were carried out in November 2007, with electronic database searches repeated in March 2010.
Study selection Eligible studies were randomised, placebo controlled trials of calcium supplements (?500 mg/day), with 100 or more participants of mean age more than 40 years and study duration more than one year. The lead authors of eligible trials supplied data. Cardiovascular outcomes were obtained from self reports, hospital admissions, and death certificates.
Results 15 trials were eligible for inclusion, five with patient level data (8151 participants, median follow-up 3.6 years, interquartile range 2.7-4.3 years) and 11 with trial level data (11 921 participants, mean duration 4.0 years). In the five studies contributing patient level data, 143 people allocated to calcium had a myocardial infarction compared with 111 allocated to placebo (hazard ratio 1.31, 95% confidence interval 1.02 to 1.67, P=0.035). Non-significant increases occurred in the incidence of stroke (1.20, 0.96 to 1.50, P=0.11), the composite end point of myocardial infarction, stroke, or sudden death (1.18, 1.00 to 1.39, P=0.057), and death (1.09, 0.96 to 1.23, P=0.18). The meta-analysis of trial level data showed similar results: 296 people had a myocardial infarction (166 allocated to calcium, 130 to placebo), with an increased incidence of myocardial infarction in those allocated to calcium (pooled relative risk 1.27, 95% confidence interval 1.01 to 1.59, P=0.038).
Conclusions Calcium supplements (without coadministered vitamin D) are associated with an increased risk of myocardial infarction. As calcium supplements are widely used these modest increases in risk of cardiovascular disease might translate into a large burden of disease in the population. A reassessment of the role of calcium supplements in the management of osteoporosis is warranted.
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