Should I stop taking calcium?

Calcium supplement pillsI generally resist changing my behavior in response to health news. Whatever research findings are touted this week could be contradicted by next week’s latest study. But I stopped taking calcium last week after reports of a correlation between calcium supplements and an increased risk of heart attacks.

Given the millions of women who faithfully take their daily calcium pills, this news reminded me of the 2002 announcement about hormone replacement therapy (HRT). After reassurance from physicians that HRT was the way to go, turns out HRT increased the risk of breast cancer, heart attacks, and strokes. With HRT, adverse effects began to show up after five years. With calcium, it’s 3.6 years.

Both incidents were complete reversals: Take it, it’s good for you … oh, wait a minute … don’t take it, it’s bad for you. Both affect a large number of people, especially women. Both were a bit of a shock for the public, I fear.

This isn’t news

Reading the news last week, you’d think no one had a clue about a possible connection between calcium and heart attacks. That’s not true. There were studies in 2008 (see here and here) suggesting a possible connection between calcium and “cardiovascular events.”

News like this reduces the public’s confidence in medicine. It’s true that vitamins and minerals are relegated to the alternative health ghetto. They’re not strictly medicine. But the public doesn’t always make that distinction. You expect your doctor to be able to advise you on calcium supplements. Or at least warn you that you shouldn’t be taking them.

The results should be treated with some caution, but …

So, I’ve been waiting to see what the National Health Service (NHS) — the gold standard on health advice, in my opinion — had to say on the matter. They frequently squash overblown health news, especially those stories with headlines designed to get the reader all riled up.

The official NHS opinion appeared today, and it found nothing to criticize in how the story has been reported. The study that found a connection between calcium and heart attacks (“myocardial infarctions”) passed inspection.

This was a well-conducted review, but its results should be treated with some caution. None of these trials originally aimed to investigate cardiovascular health and they used a variety of methods to assess and report their outcomes, both of which are issues for a review of this kind.

On this basis, people advised to take calcium by a doctor should not stop taking the supplement without consulting their GP first.

The researchers’ conclusions seem appropriate: given these findings and the widespread use of calcium supplementation “a reassessment of the role of calcium supplements in the management of osteoporosis is warranted”.

The research did not look at dietary calcium or calcium supplements in combination with vitamin D, so the safety of these is not in question.

There were qualifying reservations –

[C]aution is always needed when using trial data to make conclusions on anything other than what the trial was originally designed to examine. … Meta analyses, which combine the results of several individual trials, often have inherent limitations due to differences in study populations, methods, follow-up and assessment of outcomes

— but the conclusion stands: A 30% increase in heart attack risk when taking calcium supplements.

Could there be something else going on here?

More informative than the NHS analysis was this editorial in the British Medical Journal (BMJ), where the calcium study was published (emphasis added):

Calcium supplements, given alone, improve bone mineral density, but they are ineffective in reducing the risk of fractures and might even increase risk, they might increase the risk of cardiovascular events, and they do not reduce mortality. They seem to be unnecessary in adults with an adequate diet. Given the uncertain benefits of calcium supplements, any level of risk is unwarranted.

Why should calcium supplements increase cardiovascular risk? Calcium supplements may improve some conventional cardiovascular risk factors including blood pressure and lipids. Accumulation of calcium in the arterial wall leading to reduced compliance [elasticity] would be expected to take years, but the increased risk of myocardial infarction reported by Bolland and colleagues occurred early after calcium supplementation (median follow-up of 3.6 years).

An alternative possibility is that the increased risk of myocardial infarction is not a true effect. … The intervention [taking calcium supplements] may be changing the presentation rather than the incidence. … Although the risk of myocardial infarction seemed to increase substantially (by about 25%) with calcium supplementation this was not accompanied by an increase in mortality. Calcium supplements could simply be causing gastrointestinal symptoms that could be misdiagnosed as cardiac chest pain. However, even if calcium supplements really are safe, a neutral effect on mortality casts doubt on whether they are effective prophylaxis for fractures.

The vitamin D difference

I was a little surprised that the NHS used the phrase “not in question” when speaking of calcium supplements that contain vitamin D. That sounds a little too much like saying “those supplements are safe for now.” The NHS made the point more precisely elsewhere: “The results cannot be generalised to the use of calcium combined with vitamin D as this was not investigated here.”

Without evidence, there’s nothing to be said. That’s the premise of evidence based medicine, which informs the evaluations of the NHS. In any scientific study, you have to isolate the variables. If the analysis had looked at studies of supplements with vitamin D, it could not have made a statement about calcium.

A vitamin D deficiency has been linked to an increased risk of heart problems. It’s also been linked to increased fractures. Vitamin D aids in the absorption of calcium in the intestines. But if calcium supplements can narrow the arteries in 3.6 years, do I want to wait for the research on a vitamin D combo?

There’s admittedly some validity in the argument that there’s a difference between calcium supplements with and without vitamin D. But this point was emphasized primarily by those who sell supplements.

Health anxiety

The kicker here is that calcium supplements only slightly reduce the risk of bone fractures (according to the NHS) or are ineffective or worse when it comes to fractures (according to the BMJ). And avoiding fractures is why people take calcium in the first place.

Taking supplements is a way to reduce anxiety about health. It creates a sense – an illusion? – that we have some measure of control over our inevitable decline and death.

We live in a very anxiety-producing culture. It’s not the inevitability of death that makes us so anxious. That’s a historical constant. It’s not simply the specifics of turmoil and suffering in the world. Nor is it the underlying insecurity we feel as a side-effect of the transition to a global economy. All of those contribute to anxiety, yes. But what exacerbates our condition, in my opinion, is constant exposure to information that ultimately stands to benefit financially from maintaining a state of anxiety. That’s not a good situation.

Following health news assiduously will make you anxious and can be bad for your health. This story, however, seems worthy of attention.

Related posts:
Health news and competitive journalism
How to read health news
Direct-to-consumer: The ads we love to hate
How the pharmas make us sick
Does chocolate prevent heart disease?
HRT shrinks women’s brains? What’s wrong with this picture?

Resources:

Image source: DesignLovr

National Health Service, Calcium pills ‘may raise’ heart risk, Behind the Headlines, August 2, 2010

Mark J Bolland et al., Effect of calcium supplements on risk of myocardial infarction and cardiovascular events: meta-analysis, The British Medical Journal, July 29, 2010

John G F Cleland, et al., Calcium supplements in people with osteoporosis, The British Medical Journal, July 29, 2010

Mark J Bolland et al., Vascular events in healthy older women receiving calcium supplementation: randomised controlled trial, The British Medical Journal, January 15, 2008

Calcium Supplements in Older Women Possibly Linked to More Cardiovascular Events, Journal Watch, January 16, 2008

Emma Wilkinson, Calcium pills ‘increase’ risk of heart attack, BBC News, July 29, 2010

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