Calcium supplements are widely taken by women for bone health. However, there has been controversy about previous studies suggesting that calcium supplements may increase risk of cardiovascular disease. Now a new study of thousands of women whose health and calcium supplement use were assessed over many years finds no association between calcium supplement intake and increased cardiovascular risk. The study was published May 7 in the journal Osteoporosis International online and reported in Science Daily on May 9, 2014.
Calcium and Heart Health Q&A:
Q: Can you quickly summarize the controversial data suggesting that calcium supplements widely taken by women for bone health may increase cardiovascular risk?
A: Previous studies on the association of calcium supplements and cardiovascular disease relied on prior research designed to determine calcium supplements’ effect on rates of bone loss and fractures. Researchers found an increased rate of heart attacks in groups randomly assigned to take calcium supplements compared to groups that did not take the supplements. But while such analyses of existing data can offer the best insight into a health question at a given time, they do not provide as accurate a tool as a randomized controlled trial designed to answer the specific question. For example, the studies that were not designed to test the effect of calcium supplements on heart health were limited by small numbers of reported heart attacks and inconsistent methods to determine who in the study may have suffered a heart attack.
Q: What is the finding of the new study, and how was the study conducted? Is this finding definitive, or is more research needed to conclusively answer this question?
A: The new study we are discussing analyzed the rates of heart attack and stroke in women enrolled in the Nurses’ Health Study, conducted by mailing questionnaires to a large number of female nurses every two years starting in 1976 with questions addressing a wide range of health history and dietary and lifestyle habits. The sample under consideration included 74,245 women with 24 years’ worth of questionnaires and found no increased rate of heart attack or stroke in women who took greater than 1,000 mg/day of calcium supplements compared with those who took no supplements. In fact, the study found a slightly lower rate of heart attacks in women who took calcium supplements.
But even this study has limitations. As an observational study, the researchers can only draw inferences about the possible impact of calcium supplementation. They were unable to randomly assign subjects into a treatment group receiving calcium and a control group taking a placebo. Only a randomized study designed to determine the effect of calcium supplementation in women on cardiovascular risk can answer this question conclusively.
Q: Is it possible that women taking calcium supplements for bone health may be healthier than women who do not take the supplements? What might explain the inconsistent findings regarding calcium supplement intake and cardiovascular disease risk?
A: Women in the Nurses’ Health Study who took calcium supplements clearly lived healthier lifestyles than those who didn’t, in that they had higher levels of physical activity, smoked less, and had lower levels of trans fat intake. The investigators did try to take this into account in their interpretation of the data using a statistical technique called multivariable analysis for the baseline differences in women who did and did not take calcium supplements. Even controlling for these baseline differences, they found a lower risk of heart attack in women taking calcium supplements. The inconsistency with earlier data suggesting a higher risk likely has to do with the varied ways researchers determined whether someone had a heart attack as well as which studies were included in the meta-analyses and the inherent limitations of trying to draw conclusions about heart attack risk from studies that were not originally designed to study it.
Q: Some researchers who have investigated this topic recommend that patients and health care providers should focus on getting calcium from the diet when possible, rather than supplements. What is your thinking on this topic? Are there pros and cons to consider when choosing supplements or calcium from the diet?
A: The first choice would be to get recommended levels of calcium from diet. For example, this could be a diet containing low fat dairy—one of the main sources of dietary calcium that is also associated with lower cardiovascular risk. If levels of calcium intake are within the recommended range from dietary sources, there does not now appear to be a compelling reason to add dietary supplements of calcium. However, if dietary calcium intake is inadequate to prevent problems such as increasing bone loss, it is reasonable to take supplements.
Heart Health Q & A is a collaboration of Women’s Health Research at Yale and the OhioHealth Healthcare System, a nationally recognized not-for-profit organization with providers across 46 counties, offering a holistic approach to prevention, treatment and rehabilitation of heart disease. OhioHealth is staffed by physicians, psychologists, nutritionists and nurses who answer the questions of the moment on heart and vascular health.
The information provided here may help you make more informed choices. However, it is not a substitute for an individualized medical opinion or diagnosis, and everyone should always consult with their personal physicians to make decisions about their condition or treatment.
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