New analysis slams calcium supplements over heart problems

By Nathan Gray

- Last updated on GMT

Related tags: Calcium supplements, Calcium supplementation, Vitamin d

Researchers have warned that the indiscriminate use of calcium supplements ‘should be abandoned’, as a meta-analysis of 29,000 people suggests the risks of heart problems outweigh the potential benefits.

The new data, published in the British Medical Journal​, suggests that calcium supplements – when taken with, or without vitamin D – may increase the risk of heart attack by 25 per cent, and the risk of stroke by 15 per cent. The new findings back up the results of an earlier meta-analysis that suggested calcium supplementation could have more risks than benefits​.

Professor Ian Reid, senior author of the study, told NutraIngredients that the new data provides “a significant body of evidence that says there is a concern.”

“When we do the calculations from these 29,000 people, we find that for every thousand people we give calcium to for five years, we cause six heart attacks and we prevent three fractures,”​ said Reid.

“The message from last years study, to this years study is very consistent, and that is that it’s not a very effective way of preventing fractures, and it probably does carry a significant risk,”​ he warned.

Previous research

Last year, Professor Reid and his researcher team published a study suggesting that regularly supplementation with calcium to reduce the risk of osteoporosis may cause more heart attacks than the number of fractures they prevent.

The previous study (reported here​) looked at calcium supplementation alone, however many people take calcium combined with vitamin D, so Reid and his team then set out to see if their findings held true when this was taken into account.

Study details

Prof. Reid said that the new research was “not so much a re-analysis”, ​but a new study, which includes a re-analysis.

“What we have done is now found three studies which have calcium plus vitamin D as the intervention … that’s another 17,000 new people in which we looked at the incidence of heart attacks and strokes,” ​he explained

The results of studying these 17,000 people showed “exactly the same increase in risk from this as we found before” ​said Reid. “So then we went ahead and combined this data with the data from last year’s meta-analysis of 12,000 people to give us a total meta-analysis of 29,000 people,”

From this overall data, the researchers found a 25 per cent increase in the risk of heart attack, and a 15 per cent increase in the risk of stroke.

“Those effects are much the same as we found last year in terms of the risk size, but now because we have a much larger pool of people, the differences in the data have much higher statistical significance,” ​said Reid.

“We have a very consistent pattern … you find that in the major studies heart attack risk is very consistent, irrespective of whether or not they are taking vitamin D with the calcium,” ​concluded Reid.

Industry action

The research team are now investigating the mechanisms behind the effects of calcium supplementation to try and understand why taking supplements may pose a risk to heart health, whilst consuming calcium rich food does not.

Reid told NutraIngredients that finding the mechanisms behind the potential increased risk opens up the possibility of designing calcium supplements that are safer to use.

He confirmed that they are currently working with industry, “to look at ways or means of creating a safer way to deliver calcium to people,”​ adding that research team is happy to work more with industry “to look into these issues and try to come up with solutions.”

Prof. Reid warned that supplement manufacturers must pay attention to the risks as well as the benefits of calcium supplementation, adding that ignoring or dismissing the issue is not a suitable answer.

“The forms of supplements we are using at the minute are measurably not safe, and I think that if industry ignores that fact, or refuses to engage, it may be opening itself up to liability in the future,”​ he warned.

Close scrutiny

Industry groups have been quick to react to the study; John Hathcock, senior vice president of scientific and international affairs at the Council for Responsible Nutrition (CRN) told NutraIngredients that he “wouldn’t put a lot of weight”​ on the conclusions, adding that he believed the methodology of the study “raises more questions than it provides answers.”

“Instead of considering these findings a coincidence or a statistical abnormality as there are with many analyses of large pools of data with many variables, the authors instead suggest that the abrupt change in blood calcium levels after supplementation is what causes the effect … It seems more likely that findings are a procedural or statistical anomaly,”​ said Hathcock.

Reid responded by adding that he knew the research findings would be “a high stake statement.”​ He said the “net losers would of course be industry […] because it has substantial impact on all the people who take calcium and also on all the people who make it.”

“For that reason we have been expecting very close scrutiny and I think we have been particularly meticulous in the way we carried out this analysis so that any scrutiny doesn’t hold problems for us,”​ he said.


Source: British Medical Journal
Published online ahead of print, doi:10.1136/bmj.d204
“Calcium supplements with or without vitamin D and risk of cardiovascular events: reanalysis of the Women’s Health Initiative limited access dataset and meta-analysis”
Authors: M.J. Bolland, A. Grey, A. Avenell, G.D. Gamble, I.R. Reid

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Vitamin K2 is the answer

Posted by Doug,

It still bothers me that researchers and mass media sensationalize bunk science like Ian Reid's.

Read the following links by Dr. Know...very enlightening and I can't recommend these two posts enough.

It just goes to show how little these "researchers" know about nutrition. Anyone that actually researches bone health should know by now that vitamin K is essential for calcium metabolism.

If fact, after reading these posts, I think you'll agree that it's not the form of calcium you take, it's not whether you take magnesium (although also essential), it's not your vitamin D intake (although, again, essential)'s a lack of vitamin K.

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Effect of calcium supplements on CVD entirely predictable

Posted by Aileen Burford-Mason PhD,

Magnesium deficiency is widespread, and it was predictable from a cursory knowledge of muscle cell physiology that pushing calcium supplements on women (with or without vitamin D) and not including magnesium would eventually to be shown to be detrimental to heart health.

Most of the body’s calcium is in bone, but a critical portion is stored in the sarcoplastic reticulum of muscle cells, where it is required for muscles to contract when triggered to do so by nerves. After the muscle contracts, magnesium is essential to removing the calcium back into storage before muscles can relax again. This basic mechanism is important not only for the proper functioning of skeletal muscle, but also cardiac muscle and the smooth muscle cells of blood vessels that control blood pressure.

Just understanding this interdependence of calcium and magnesium in muscle cell relaxation and contraction, and the knowing how widespread magnesium deficiency was in western diets should have alerted physicians to the dangers of calcium supplementation alone.

Animal studies have demonstrated just how detrimental excess calcium can be to heart muscle, in that it causes mitochondrial degeneration in heart, liver and kidney. This damage is more severe if you supplement magnesium-depleted animal with calcium [1].

[1]. Effects of dietary magnesium deficiency in the rat with special reference to ultrastructural examination. Ikeda T et al. Kokuritsu Iyakuhin Shokuhin Eisei Kenkyysho Hokoku 1997;115:112-118

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Missing link

Posted by Julie Vincent,

The missing link in the assimilation of Calcium is not just Magnesium Vitamin D and Vitamin K but Vitamin K2. This is an essential vitamin as we no longer seem to be able to manufacture sufficient quantities in the large bowel due to changes in diet. It is not added to vitamin supplements due to its high cost of manufacturing from Natto.

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