Two studies published in the past two years have been heavily reported in the media, suggesting that calcium supplements may be associated with an increased risk of heart attacks and strokes. Bolland et al specifically examined the relationship of calcium with the risk of heart attacks and cardiovascular events in a 2010 BMJ meta-analysis. Trials that included vitamin D as an intervention were excluded. Overall, the analysis suggests that calcium supplements did increase the relative risk of heart attack by about 30%. Many of our clients, who tend to be very well-educated and out-of-the-box thinking women to begin with, have recently wondered if this is, in fact, true and have raised the question “Could the risks of calcium supplements outweigh any benefits they offer?”
So… to the women of our practice who ask these great questions and take personal responsibility for their health – I applaud you… and hope to shed some light on the subject here.
Osteoporosis is a progressive bone condition of reduced bone mass and deterioration of bone tissue, with a correlating increase in fracture risk. Eighty percent (80%) of those diagnosed are women. Hips and spines are the most common fracture locations, but they can appear in any bone, and osteoporosis makes fractures more likely. In postmenopausal women over the age of 50, the lifetime risk of a vertebral fracture is about one in three, and one in five for a hip fracture. This makes prevention and treatment major health issues!! Osteoporosis prevention and treatment guidelines recommend calcium and vitamin D as an important measure in preserving bone density and reducing the risk of fractures.
In order to give a good answer to this question, we researched to find out what happened after this paper was released. We found out that there were criticisms of the endpoints, and that the composite endpoint was not considered significant. Concerns were also raised that the trials included were not designed with cardiovascular endpoints, which is a valid criticism. In addition, many reviewers pointed out that the studies excluded vitamin D, which is contrary to treatment guidelines and common use. Now the same group of researchers have done a new analysis, incorporating vitamin D. Bolland and associates followed up their calcium-only therapy with a study of calcium plus vitamin D. They used the Women’s Health Initiative (WHI) dataset to answer the vitamin D question, added in some other studies, and redid their meta-analysis.
The WHI was a massive 15-year trial of over 161,000 women that sought to answer a number of questions about women’s health. The calcium and vitamin D study was a component of the WHI which randomized 36,282 postmenopausal women aged 50-79 into two groups. One group received 1,000 mg of calcium carbonate and 400IU of vitamin D once daily, and the other received placebos. It is interesting to note that in the design, 54% of the women were already taking calcium, and 47% were already taking vitamin D, and they were allowed to continue with their therapy, even after randomization. In the over 16,000 women not taking their own calcium and vitamin D, there was a significant increase in heart attacks noted in the group randomized to calcium and vitamin D. In contrast, women taking their own calcium and vitamin D didn’t show any changes in their cardiovascular risk when randomized to calcium and vitamin D. In addition, no relationship was found between calcium dose and risk of cardiovascular events.
So, weighing through these studies was confusing to say the least. In any case, it does indicate that taking calcium supplements may slightly raise the odds of a heart attack in postmenopausal women. However, there are many reasons for why that may be a factor in this study and all researchers seem to be quite clear that there is no direct connection that has been established.
According to the Wall Street Journal (April 21/11):
Physicians say there’s still no solid evidence of a cause-and-effect relationship, and that while more research is needed, the study shouldn’t scare women away from supplementing with calcium up to the recommended daily level.
Researchers from the University of Auckland and University of Aberdeen took data from a large Women’s Health Initiative study on calcium and vitamin D consumption and used it to update their analysis of previously published research. That WHI study found no overall ties between calcium supplement use and heart problems, but more than half of the participants had already been taking calcium supplements when it started. So in many women, the study wasn’t actually comparing the difference between no calcium and some, but between some calcium and even more calcium.
The researchers say that if supplements do increase risk, it may be because large amounts of calcium in the blood may harden arteries or cause clots.
Bess Dawson-Hughes, director of the Bone Metabolism Laboratory at the Nutrition Research Center on Aging at Tufts University, says this latest research can’t provide any definitive answers about whether calcium supplements are tied to heart disease.
Separating the women in the WHI who took supplements on their own from those who didn’t produces groups of women with very different health profiles, she says. It’s not possible to say whether the increased rate of heart problems in the group that wasn’t using personal supplements is due to the calcium supplementation or other factors. Other research has shown that people who take supplements are healthier in general than those who don’t.
Other sources that we really respect indicate the same thing as this review. One thing that does seem to be a pre-cautionary bit of advice is to not “over-supplement” with calcium. Incidentally, we have been recommending well below the conventional usual “prescription” of 1200mg/day level in our practice for years — mostly because we already get calcium from diet and we are individualizing supplementation to the individual instead of using broad “general protocols”. We also very much believe that the “source” of the calcium is important and that these studies are referring to calcium carbonate – not a form that we usually recommend due to its poor absorption in the body. It is our belief that we will have a more clear answer to this question over time, but for now appropriately dosed supplementation of a good quality calcium complex, complete with vitamin D and trace minerals is still an important part of osteoporosis prevention.
Naturopathic Doctor
Clinic Director
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