‘Risks outweigh benefits’ for calcium supplements: Meta-analysis

By Nathan Gray

- Last updated on GMT

Related tags: Calcium supplements, Myocardial infarction, Hip fracture, Osteoporosis

Regularly taking calcium supplements for osteoporosis may cause more heart attacks than the number of fractures they prevent, according to new research.

The study, published in the British Medical Journal​, suggests that calcium supplements – which are commonly taken by older people to reduce the effects of osteoporosis – may increase the risk of cardiovascular events , such as heart attacks and stroke, by up to 30 percent.

Professor Ian Reid, senior author of the study, told NutraIngredients.com that he believes the findings indicate a need to review the use of calcium supplements in the general population; saying that the industry needed to “sit back and not just look at the benefits, but the clearly demonstrated risks”.

“When you do the arithmetic, then it just doesn’t add up. The risks outweigh the benefits,” ​said Prof. Reid, from the University of Auckland, New Zealand.

Calcium

The widely used supplements have been shown to marginally reduce the risk of fracture for osteoporosis sufferers, and improve bone density. However, the authors noted that very little research has been compiled on the risks associated with calcium supplementation.

The results observed in the new study – a meta-analysis of fifteen randomized trials on calcium supplements conducted in the last twenty years – saw an increased risk of cardiovascular events in people using calcium supplementation but not people with high dietary intakes of calcium.

Prof. Reid explained that this may be related to supplements causing higher blood calcium levels compared to dietary calcium – high blood calcium levels are believed to lead to hardening of the arteries, which can cause heart attacks.

Heart risk

The study investigated the links between calcium supplementation and cardiovascular events by analyzing data from over 12,000 people involved in 15 trials.

They found that calcium supplements increase the risk of heart attack by about 30 percent.

“The likely adverse effect of calcium supplements on cardiovascular events, taken together with the possible adverse effect on incidence of hip fracture and its modest overall efficacy in reducing fracture (about 10 percent reduction in total fractures) suggest that a reassessment of the role of calcium supplements in the prevention and treatment of osteoporosis is warranted,”​ said the researchers.

They added that, although the increase in heart attack risk is modest, the widespread use of calcium supplements means that “even a small increase in incidence of cardiovascular disease could translate into a large burden of disease in the population.”

Wider impact

Reid told NutraIngredients.com that he also believes the study has broader implications for all nutritional supplements:

“We have tended to focus on just the benefits of supplements without really looking at their safety. In the future I think we need to look at both the efficacy and the safety of supplements,”​ said Reid.

“People assume that these supplements are natural. A high calcium meal is natural, but taking highly concentrated calcium tablets is not, and does not have the same effects,”​ he warned.

Industry response

The Health Supplement Information Service responded to the research findings saying: “While the results of this meta-analysis are interesting and should encourage more research, the authors did not include the totality of the evidence on calcium supplementation and there were limitations to the analysis. For these reasons, it is not appropriate at this stage to change public health advice on the use of calcium supplements to maintain bone health."

Further industry responses to this study can be found here​.

Source: British Medical Journal
doi:10.1136/bmj.c3691
“Effect of calcium supplements on risk of myocardial infarction and cardiovascular events: meta-analysis”
Authors: M.J. Bolland, A. Avenell, J.A. Baron, A. Grey, G.S. MacLennan, G.D. Gamble, I.R. Reid

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3 comments

too many variables

Posted by Dan DeFigio, www.gettingfit.com,

Excellent points above -- thank you both!
Don't forget vitamin K (both K1 and K2) which are vital for bone formation. If you are vitamin K deficient, no amount of calcium will build a molecule of new bone.

If the study were to look at heart risk vs. decreased fracture risk in those who took a complete nutrition package instead of just calcium, I'll bet the risk ratios would be very different.

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Researchers hand picked studies which would support their thesis

Posted by Mike Hall,

A meta-analysis simply reviews previous studies, eliminating those which do not fulfill the criteria of the authors and analyzing them all. In this study there were 190 possible papers, and of these only fifteen were included. Of these 15 papers, only 65% had data on cardiovascular events, and it is hard to see why they were included. In this selected group of patients there was in fact a higher incidence of heart disease and strokes.

However this study deliberately excluded any papers where vitamin D was given in addition to calcium. The reason being that other studies had shown that calcium and vitamin D has no adverse effect on heart disease, and could possibly be beneficial.
Thus this paper has no relevance at all to people taking supplemental calcium plus vitamin D and magnesium. People taking supplements which include vitamin D, do not to need to be concerned as this study does not apply to them.

There is no study showing that people taking calcium supplements plus some vitamin D has any adverse effect on the heart or strokes, and the authors of this study agree with this statement. In addition there are studies [the Women's Health Initiative] which showed that calcium and vitamin D do not increase the risk of cardiovascular disease. Therefore people taking this combination may continue to do so in confidence that there is no evidence that it is anything other than beneficial.

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Calcium that is not absorbed and used by the body

Posted by Fran Gare, ND,

Supplements can not be used in isolation of other nutritional substances. They do not occur in foods alone. Calcium need vitamin D, B-6, magnesium and boron to be properly metabolized by the body. Giving large does of a single nutrient is stacking the deck against it.

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