tag:theconversation.com,2011:/fr/topics/osteporosis-1574/articlesOsteporosis – The Conversation2012-06-20T20:44:39Ztag:theconversation.com,2011:article/72822012-06-20T20:44:39Z2012-06-20T20:44:39ZCan calcium supplements cause heart disease?<figure><img src="https://images.theconversation.com/files/11385/original/4dm79x8k-1338861850.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">There’s no evidence suggesting that a calcium-rich diet causes heart problems.</span> <span class="attribution"><span class="source">Rachel James</span></span></figcaption></figure><p>People taking calcium supplements to mitigate their risk of developing bone disease (osteoporosis) may be doing more harm to their health than good. That’s because a growing body of research shows the supplements confer little benefit and increase the risk of developing heart disease. </p>
<p>Calcium supplements have also traditionally been thought to reduce the risk of heart attacks because they produce small beneficial changes in both blood pressure and blood cholesterol levels. We set out to test this idea in a trial we had originally designed to check the effect of calcium supplements on fractures and bone density. </p>
<p>To our surprise, what we <a href="http://www.bmj.com/content/336/7638/262">discovered</a> was that heart attacks were actually more common in the (randomly selected) women who received calcium supplements than those who had randomly been given inactive tablets.</p>
<p>When we <a href="http://www.bmj.com/content/336/7638/262">published this study</a> in the <a href="http://www.bmj.com/">British Medical Journal</a> in 2008, it caused widespread surprise among doctors working in the area, as well as the general public. So to test whether this was the true effect of calcium supplements, we decided to do a <a href="https://theconversation.com/how-do-we-know-what-works-systematic-research-reviews-5979">meta-analysis</a> of studies about taking them.</p>
<p>First, we contacted all the researchers who had carried out large trials of calcium supplements in the past to see whether they’d kept records of the medical problems that occurred in the course of the trials. </p>
<p>Data were available from 93% of trial subjects (almost 12,000 people) and these confirmed our finding that women who received calcium tablets in the studies had a 20% to 30% <a href="http://aura.abdn.ac.uk/bitstream/2164/756/1/Bolland%202010.pdf">increase in heart attack risk</a>. </p>
<p>We subsequently added to this database the results from other trials in which the <a href="http://www.bmj.com/content/342/bmj.d2040">intervention was calcium and vitamin D</a>, rather than calcium alone. This showed the same effect – a 25% increase in the risk of heart attacks and a 15% increase in the risk of stroke. </p>
<p>These results were based on almost 29,000 people participating in research and so were much more reliable than the results we had published previously. </p>
<p>From these analyses, we were able to determine that the number of heart attacks and strokes apparently caused by calcium supplements was greater than the number of fractures that they appeared to prevent. Naturally, we concluded that the use of calcium tablets was likely to be doing more harm than good and should be discontinued.</p>
<p>It’s very important to note that none of our analyses included the effect of calcium-rich foods, and there’s really no evidence suggesting that a calcium-rich diet causes heart problems.</p>
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<img alt="" src="https://images.theconversation.com/files/11382/original/mgdzxkbc-1338861666.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/11382/original/mgdzxkbc-1338861666.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=844&fit=crop&dpr=1 600w, https://images.theconversation.com/files/11382/original/mgdzxkbc-1338861666.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=844&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/11382/original/mgdzxkbc-1338861666.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=844&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/11382/original/mgdzxkbc-1338861666.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1060&fit=crop&dpr=1 754w, https://images.theconversation.com/files/11382/original/mgdzxkbc-1338861666.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1060&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/11382/original/mgdzxkbc-1338861666.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1060&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="attribution"><span class="source">Matt Reinbold</span></span>
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<p>The reason for the difference between tablet supplements and food remains uncertain, but it may be related to the increase in blood calcium level that’s seen for several hours following the large dose of calcium in tablet form. In contrast, calcium in food is absorbed more slowly and has very little impact on blood calcium levels. </p>
<p>Elevations of blood calcium levels have previously been shown to <a href="http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2265.2010.03792.x/full">increase the risk of heart disease</a>, possibly through producing calcium deposits in the walls of blood vessels and accelerated arterial disease.</p>
<p>A number of <a href="http://www.sciencedirect.com/science/article/pii/S0378512209000954">other researchers have now looked</a> into these questions. This month, <a href="http://heart.bmj.com/content/98/12/920.full.pdf">researchers from Germany reported</a> that individuals taking calcium supplements appear to almost double the risk of heart attacks compared with people not taking supplements. And again, those who have high dietary calcium intakes tend toward lower risk of heart disease. </p>
<p>The German study didn’t randomly assign participants into groups taking calcium or placebo tablets, but simply reported events in individuals who had made the decision to take supplements independently. This is a less reliable way of determining the effects of an intervention than a randomised trial. Nonetheless, this observational study provides supportive evidence for the results of our trial analyses.</p>
<p>Last year, <a href="http://www.sciencedirect.com/science/article/pii/S0378512211001526">researchers in Sydney studied</a> the effects of calcium supplements in a very elderly group of individuals living in hostels. One-third of the 600 people in the group died during follow up. Death rates increased by 47% in those randomised to calcium and death from heart disease was increased by 76%.</p>
<p>So the weight of evidence that calcium supplements are bad for the heart has steadily increased. What, then, should people do in the face of these findings? </p>
<p>Calcium supplements are mainly used to reduce the risk of fractures from osteoporosis (a bone disease that leads to increased likelihood of fracture). But there are other important measures that will also contribute to osteoporosis prevention, such as regular exercise, not smoking, maintaining a healthy body weight, regular sunlight exposure to maintain vitamin D levels, and removal of falls hazards in the home (such as loose rugs, power cords, and slippery floors). </p>
<p>A steady supply of calcium is important for bone health, but research clearly shows this should be derived from a balanced diet that includes several servings of dairy products, or other calcium sources, such as dark green vegetables or tofu. </p>
<p>Women in their 60s and men in their 70s should have their risk of osteoporotic fractures formally assessed. This usually involves bone density measurement. </p>
<p>People found to be at high risk of fractures should consider using one of the medicines proven to safely reduce fracture risk. This is likely to be more effective than relying on the weak anti-osteoporotic effects of calcium supplements, which come at an unacceptably high price – the increased risk of heart disease.</p><img src="https://counter.theconversation.com/content/7282/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Ian Reid consults to Sanofi and receives funding from Health Research Council of New Zealand.</span></em></p>People taking calcium supplements to mitigate their risk of developing bone disease (osteoporosis) may be doing more harm to their health than good. That’s because a growing body of research shows the…Ian Reid, Deputy Dean & Professor of Medicine, University of Auckland, Waipapa Taumata RauLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/66482012-04-24T01:48:31Z2012-04-24T01:48:31ZProtein could help treat bone and joint diseases<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/9885/original/5xxm5nbc-1335231801.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/9885/original/5xxm5nbc-1335231801.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=900&fit=crop&dpr=1 600w, https://images.theconversation.com/files/9885/original/5xxm5nbc-1335231801.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=900&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/9885/original/5xxm5nbc-1335231801.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=900&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/9885/original/5xxm5nbc-1335231801.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1131&fit=crop&dpr=1 754w, https://images.theconversation.com/files/9885/original/5xxm5nbc-1335231801.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1131&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/9885/original/5xxm5nbc-1335231801.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1131&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">Half of all women over the age of 50 are expected to suffer at least one osteoporotic fracture.</span>
<span class="attribution"><span class="source">AAP/Robert McGrath</span></span>
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<p>A protein with a bone-protective effect could help in the development of more powerful treatments for osteoporosis and other bone diseases, an international team of scientists has reported.</p>
<p>The protein, called semaphorin 3A (Sema3A), is expressed by cells that are responsible for bone formation. Mice treated with the protein showed improvements in their bone health, the team of researchers reported in the latest edition of Nature.</p>
<p>Osteoporosis affects <a href="http://www.aihw.gov.au/publication-detail/?id=10737418750">almost 700,000</a> Australians, or more than 3% of the population. Women account for 82% of all cases, which occur mainly in people over the age of 55 years.</p>
<p>Hiroshi Takayanagi, from the Department of Cell Signaling, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, and the Centre for Orthopaedic Research at The University of Western Australia, said the discovery could “lead to better treatment developments for osteoporosis, arthritis or bone fractures. I also think Sema3A could be used as a bio-marker for disease diagnosis because we found that in the older mice where the amount of bone was dropping, the amount of Sema3A protein had also decreased.”</p>
<p>Professor Takayanagi and his team found that bone forming cells, or osteoblasts, produced Sema3A, which was previously known to regulate nerve and immune cells.</p>
<p>When used to treat mice, not only did Sema3A decrease bone breakdown but, unlike current osteoporosis medications, it also boosted bone formation.</p>
<p>“Osteoporosis treatments available today largely involve taking medication which suppresses bone resorption, but these drugs also suppress bone formation,” Professor Takayanagi said. “It has been hoped someone can develop a new drug which can control both bone resorption and formation to help recover the normal amount of bone.</p>
<p>"Our research team looked at Sema3A, a protein produced by osteoblasts which controls the development of neuron paths and inhibits T-cells in the body’s immune system. When we treated mice with Sema3A we found the protein was suppressing bone breakdown and speeding up bone formation at the same time.”</p>
<p>Gethin Thomas, Deputy Director of Education and Senior Research Fellow in the Muscoskeletal Genetics Group at The University of Queensland Diamantina Institute, said the burden of osteoporosis to the general community was “considerable”. Half of all women over the age of 50 were expected to suffer at least one osteoporotic fracture, Dr Thomas said.</p>
<p>“Most current approaches for osteoporosis therapy decrease the activity of osteoclasts to decrease bone degradation, but the gold standard is to find therapies that can build bone as well as stop bone degradation, as osteoporosis is frequently only diagnosed after the bones have already become very weak.</p>
<p>"This is a very exciting discovery identifying a completely new bone regulating pathway and one that is potentially very "druggable”. Indeed in this study they have shown that treating mice with Sema3A results in increased bone strength.“</p>
<p>But the pathway to a drug would provide many challenges, said T.J. Martin, Emeritus Professor of Medicine in the Bone Cell Biology and Disease Unit at St Vincent’s Institute of Medical Research and the University of Melbourne.</p>
<p>"The treatment studies in the paper are limited, but the control pathway revealed in the genetic experiments is of great interest, posing many further questions,” Professor Martin said. Although it is not easy to see Sema3A itself as a drug, it provides much that will influence thinking as attempts are made to develop the “holy grail” of an inhibitor of breakdown that promotes bone formation.“</p><img src="https://counter.theconversation.com/content/6648/count.gif" alt="The Conversation" width="1" height="1" />
A protein with a bone-protective effect could help in the development of more powerful treatments for osteoporosis and other bone diseases, an international team of scientists has reported. The protein…Justin Norrie, EditorLicensed as Creative Commons – attribution, no derivatives.