A recent study published in the online version of the British Medical Journal that casts doubt on the value of calcium supplementation and links the ingredient to an increased risk for heart attack has sent a shock wave through the dietary supplements industry.
In the study released Thursday – a meta-analysis of data from 15 clinical calcium supplementation trials – a team led by Professor Ian Reid at the University of Auckland, New Zealand, concluded that calcium administered without vitamin D was associated with a roughly 30 percent elevated risk of heart attack. These results applied only to calcium supplements, not to calcium in the diet, whose benefits were not questioned.
However, “the jury is way out on this one,” said Robert Heaney, MD, a renowned calcium researcher at Creighton University in Nebraska who provided some of the studies analyzed by the New Zealand researchers but was not otherwise involved in the actual published study. “The paper is highly suspect. We provided some data for the authors. The senior author rejected some of the cases we provided. In all our studies, our findings were the exact opposite. As always with meta-analyses, it depends on which studies you include and which you do not.”
Earlier studies in 2008 and 2006 had clouded the calcium picture. Results from those studies indicated that the extra calcium did raise levels of calcium in the bones somewhat, but seemed to do little to help prevent fractures.
The study released Thursday concluded, “Even a small increase in incidence of cardiovascular disease could translate into a large burden of disease in the population.” It went on to say, “A reassessment of the role of calcium supplements in the prevention and treatment of osteoporosis is warranted.”
Industry groups have been quick to respond. On Thursday the Council for Responsible Nutrition issued a statement questioning the study’s conclusions and methodology.
“Adequate calcium intake is vital to building and maintaining healthy bones, and to preventing osteoporosis,” said Andrew Shao, Ph.D., head of scientific and regulatory affairs at CRN “The results from this meta-analysis does not undermine the value calcium supplements offer to those concerned with maintaining or increasing bone density, as years of research shows these products do.”
CRN specifically question the decision by the study’s authors to confine their analysis to only 15 studies, when more than 300 clinical trials on calcium supplementation are available. And the group also highlighted the shortcomings of the meta-analysis process itself, in which data from a number of sources is statistically analyzed to try to spot overarching trends.
Taken together, CRN judged the study’s conclusions to be “dramatically overstated.”
Not all agree with that conclusion, however, even within the natural products business. Industry insider Bill Sardi has lectured for years on the deleterious role of too much calcium taken as supplements and its role in the development of arterial plaque. In a letter to CRN Sardi said, “The cholesterol theory of artery disease should be abandoned as John Abramson M.D. of Harvard, author of ‘Overdosed America,’ has shown that while statin cholesterol-lowering drugs do reduce circulating lipids, there is no evidence statins reduce mortality; 50% of arterial plaque is calcium, only 3% is cholesterol.”
Sardi went on to say that he suggests “the industry back away calcium supplementation as a broad recommendation for menopausal women.”
Heaney said there “would be some market potential in combining nutrients” in a formulation, especially because most people are also deficient in vitamin D. Other notable bone-health nutrients include vitamin K2, phosphorus and boron.