Do Calcium Supplements Cause Heart Attacks?
Patients have been seeing another media cycle of great enthusiasm followed by deep disappointment about the supposed benefits of a dietary supplement. We are now hearing that calcium supplements may actually cause heart attacks. A new paper shows a modestly increased risk of heart attack or stroke in women who take calcium supplements. So the small potential risk must now be taken into account when compared to the minimal benefit these supplements offer in preventing fractures and osteoporosis.
We have seen this story before, where beta carotene, folic acid, B vitamins, Vitamin C, Vitamin E, and others were widely touted to improve health, until we were finally told that they have no benefit and may possibly cause harm.
How could this happen over and over? The answer lies in the way scientific research slowly progresses towards its’ ultimate conclusion.
Observational Studies are Suspect
A lot of medical research is done by looking at existing populations to find statistical associations between some type of treatment, like calcium, and some type of medical outcome, like heart attacks or cancer. The flaw in this type of observational study is that all kinds of unanticipated factors may be associated with the use or non-use of the treatment, and these factors will often bias the result of the study. For instance, the kind of people that take vitamin supplements tend to be more health conscious and healthier than those who don’t take them. The investigators have no way of totally correcting for such flaws, so observational research often turns out to be wrong.
Meta-analysis Studies are Not Much Better
Another kind of medical research takes previously performed studies that were designed to answer one medical question, and then go back to reanalyze the data to answer a different question that was not part of the original study design. Often several studies that were all designed differently are cobbled together so that there are enough patients to make the statistics work. The flaw in this type of meta-analysis study is that the question that it tries to answer was often not part of the original studies. Also, unpublished studies that address the same question are not available for analysis, biasing the conclusion. As a result, meta-analysis studies are also often unintentionally biased and wrong.
The Gold Standard: Randomized Double Blind Studies
The type of study that is most scientifically valid and relatively conclusive, is the randomized double-blind study. In this type of study, investigators randomly give a treatment or a placebo to a large number of people so that neither the patients nor the investigators are aware of who is getting what treatment until the study code is broken. These randomized double blind studies are hugely expensive and difficult to carry out. Nevertheless, they are considered the “Gold Standard” of medical research because they remove intentional and unintentional bias.
Each of the vitamin and supplement manias that we have experienced occurred because the media loves a good story about the lifesaving effects or the dangers of a simple vitamin or supplement – even if the news is based on the weak science of observational studies or meta-analysis. It takes years to get good randomized double-blind studies organized and performed, and by then the media-fueled mania is at its peak, only to burst when good randomized double-blind studies are published.
Are Calcium Supplements OK to Take?
So it is with the latest calcium warning. The meta-analyses showing that calcium supplements are associated with heart attacks, strokes, and death in elderly women is interesting, but not the final word at all. Until the strong science of the randomized double-blind study sorts it out, the alternative of getting your calcium from dairy products and leafy green vegetables is a good option if the news hype is making you too nervous. If you don’t have a very good reason to be taking calcium supplements under medical supervision, and you haven’t questioned your doctor about the heart attack and stroke risks, you just may want to stick with the dietary approach for now.