The research team was led by Professor Sabine Rohrmann of the Division of Cancer Epidemiology and Prevention, Institute of Social and Preventive Medicine at the University of Zurich in Switzerland. In an interview with Nutraceuticals World, Dr. Rohrmann said she and her colleagues were drawn to previously established connections between calcium supplementation and heart attack risk. “We knew of meta-analyses that already indicated an increased risk of MI (myocardial infarction) among calcium supplement users,” she said. “We wanted to examine this in a non-clinical setting.”
The researchers culled data from 23,980 Heidelberg cohort participants of the European Prospective Investigation into Cancer and Nutrition study, who were aged 35–64 years and had not experienced major cardiovascular disease (CVD) events at the time of recruitment. In a nutshell, during a follow up period that spanned eleven years, 354 MIs, 260 stroke cases, and 267 CVD deaths were documented. The researchers concluded that the numbers indicated calcium supplements “might raise MI risk” and “should be taken with caution.”
When asked if specific doses of supplemental calcium proved more detrimental than others, Dr. Rohrmann said dosage levels were not tracked in her study. “In most clinical trials the usual dose is 1000 mg/day,” she said. “Based on or results we cannot give information on a safe dose. For this, we need a study with better assessment of dose and frequency of use.”
She went on to add that as a nutritionist, her recommendation was that calcium intake should come from dietary sources such as low fat dairy products, and vegetables like kale rather than from pills. “Also, some orange juices are supplemented with calcium but at a lower dose than a usual supplement,” she said. “If at all, people should think about splitting up their daily dose into smaller portions.”
Dr. Rohrmann said she planned to continue studying this phenomenon. “My next step will be to examine if individuals who use calcium supplements do indeed have higher serum levels of calcium, which is a possible explanation for our finding,” she said.
The Industry Responds
Given calcium’s increasingly important and trusted role in the realm of bone health, dietary supplement groups were quick to counter the media coverage that warning consumers about calcium pills.
“Calcium is an important mineral with proven benefits for bone health and a long history of safe use backed by an extensive body of observational and clinical studies that supports its use for reducing the risk for osteoporosis and hip, bone and other fractures. In addition, research has shown positive effects on risk factors associated with heart health,” said Taylor C. Wallace, Ph.D., senior director, scientific & regulatory affairs for the Council for Responsible Nutrition (CRN). “This study itself is not reason enough to discount the important benefits of calcium, but consumers with questions—as well as their doctors—should consider these following points: The original study wasn’t designed to measure cardiovascular events; consequently confounding factors for cardiovascular disease were not equally distributed across the study groups. So, for example, the calcium supplement group had a population with a greater incidence of high cholesterol at baseline, and also included more smokers who were more likely to smoke for a longer duration. (The association between smoking and heart disease is well-established.) In terms of considering the relative risk, of the 851 individuals taking supplements containing calcium, only seven events occurred in users of supplements containing only calcium.”
Dr. Wallace added that for those at prone to falls and fractures due to weak bones, removing calcium supplements from the diet could create an even greater health risk. “Our advice is for consumers to be aware of how much calcium they get from their diet, supplement with calcium if needed, and check with their doctor or other healthcare practitioner to determine their own personal needs.”
Dr. Cara Welch, vice president of scientific and regulatory affairs, for the Natural Products Association (NPA), concurred with Dr. Wallace and disputed points within the study’s methodology. “It’s important to note that this study was not set up to look at cardiovascular disease,” she said. “The sub-population this study looked at, users of calcium supplements alone, was very small compared to the total group, with an older average age as well as a longer duration of smoking. Meanwhile, the benefits of calcium are well-accepted. In fact, the Food and Drug Administration has approved a health claim on the use of calcium with regard to osteoporosis.”
Dr. Welch also added that the National Institutes of Health Office of Dietary Supplements agreed that calcium does not negatively affect the heart. “They have stated that, ‘Calcium has been proposed to help reduce cardiovascular disease risk by decreasing intestinal absorption of lipids, increasing lipid excretion, lowering cholesterol levels in the blood, and promoting calcium influx into cells,’” she said. “Results from other prospective studies have shown no significant associations between calcium intake and cardiac events or cardiovascular mortality.”
She concluded that NPA did not believe that the published study should cause consumers to stop taking their calcium supplements. “Calcium supplements are important for those Americans who do not get the appropriate amount of calcium in their diet,” she said. “We recommend you discuss your calcium intake with your health care professional.”