DOES CALCIUM CAUSE HEART ATTACKS?
Sep 21, 2010
By Trevor Shewfelt, Pharmacist at the Dauphin Clinic Pharmacy
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The information in this article is intended as a helpful guide only. It is not intended to be used as a substitute for professional advice. If you have any questions about your medications and what is right for you see your doctor, pharmacist or other health care professional.
Who knew a census could be exciting? This summer, Stephen Harpers Conservative Government told everyone they were going to get rid of the long form census. This got everyone from Francophones to Municipal Governments to businesses excited. You see many, many people rely on the information from the census to make their policy decisions. The Harper Conservatives said the long form census was intrusive. They didnt like that the current legislation threatened jail time if someone didnt complete it. The part of the debate I found exciting, though, was the lie. Industry Minister Tony Clement said Statistics Canada believed the information collected from a voluntary survey would be as accurate as that from a mandatory census. This lie so upset head of Statistics Canada, Munir Sheikh, that he quit in protest.
There was another mis-truth this summer that more directly affected me. I not saying the media lied when they started saying calcium supplements caused heart attacks, but it wasnt the whole truth. Let me tell you my story. I had a customer in her seventies call me out to the vitamin aisle. She had been taking calcium supplements for years, but now she had heard that it would cause heart attacks. She wanted to know how much calcium she should take to keep her bones strong, but not so much as to give her a heart attack.
Where did this fear inspiring headline come from? There was a study done in New Zealand and published in the July 29, 2010 British Medical Journal by Mark J. Bolland et al. The study was a meta-analysis. Although different types of studies might sound boring, this is important. The best type of study is called a double-blind placebo controlled trial. In this type of trial a drug is given to half the study participants and a sugar pill is given to the other half. Neither the study participants nor the researchers know who gets what until after the study is over. That way we can be sure that an effect found in the drug group was really caused by the drug. A meta-analyis is different. The researchers in New Zealand never ran a trial at all. They took a bunch of other peoples trials, threw the results into a computer and looked at what came out. A meta-analyis has several inherent problems. Were the researchers biased when the picked the trials they included? Were the trials done in similar ways? You cant mash an apple and an orange together and expect to get apple sauce just because they are both fruit. In the same way, not all studies are set up the same way and their results cant always be mashed together.
Meta-analyses are not terrible things. But, I my opinion, they should usually be done to generate a new hypothesis for a new double-blind placebo controlled trials to test. They shouldnt be plastered all over the news as the truth. When a meta-analysis hits the papers saying calcium supplements cause heart attacks, people over react. This meta-analysis from New Zealand said people over the age of 40 who take 500 mg or more of calcium per day have more heart attacks than those who dont. One theory to explain this is that too much calcium might harden the blood vessels.
Dont throw out your calcium supplements yet. Remember this was a meta-analysis. In fact another meta-analyis published by Wang, et. al in the March 2, 2010 Annals of Internal Medicine looked at this issue from a slightly different angle. They looked to see if calcium plus Vitamin D prevented heart problems. The studies they looked at showed a some evidence Vitamin D prevented heart problems, but it wasnt strong. They found calcium didnt seem to effect heart problems one way or the other. So the experts havent decided yet if calcium effects the heart or not. So you shouldnt stop your calcium because you are worried about heart attacks. The jury is still out on that.
Why should you take calcium supplements? The main reason to take calcium is to help keep your bones strong. The current recommendation is 1000-1200 mg of calcium per day. Should you take them with or without Vitamin D? Calcium should be taken with Vitamin D because Vitamin D helps the gut absorb calcium. The current recommendation is 800 to 2000 IU of Vitamin D per day. If we treat 50 post-menopausal women with 1000 mg of calcium per day for 5 years, we will prevent one fracture. As we get older a broken bone is not just an inconvenience. It can mean the difference between staying in your own home or ending up in a hospital or nursing home. Another study by Haentjens et. al in March 16, 2010 Annals of Internal Medicine says older adults are 5-8 times more likely to die in the first 3 months after a hip fracture than people their age that didnt break a hip. So the benefits of calcium and Vitamin D can be huge.
So remember not everything you hear from a politician or on a new report are always true. Get a second opinion before the next health story you hear on the news makes you want to panic.
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BMJ Article: Effect of calcium supplements on risk of myocardial infarction and cardiovascular events: meta-analysis - http://www.bmj.com/content/341/bmj.c3691.full
Annals of Internal Medicine abstract: Systematic Review: Vitamin D and Calcium Supplementation in Prevention of Cardiovascular Events - http://www.annals.org/content/152/5/315.abstract
As always if you have any questions or concerns about these products, ask your pharmacist.