CRN Counters Two Recent Studies Questioning Calcium Safety

The Council for Responsible Nutrition (CRN; Washington, DC) has responded to two February-published research studies questioning the safety of supplemental calcium nutrition.

The first study, “Dietary and supplemental calcium intake and cardiovascular disease mortality,” (Q Xiao et al.) published in the Journal of the American Medical Association Internal Medicine, looked at potential adverse effect of high calcium intake on cardiovascular health. Specifically, researchers hoped to investigate whether intake ofdietary and supplemental calcium is associated with mortality from cardiovascular disease (CVD). Researchers looked at data from the National Institutes of Health’s AARP Diet and Health Study, a prospective study that took place in 1995–1996 and that enrolled 388, 229 men and women aged 50 to 71 years.

Researchers found that while calcium intake from dietary sources was not related to CVD death, in men, supplemental calcium intake (intake from supplements) was associated with an elevated risk of CVD death. (In women, supplemental calcium intake was not associated with CVD death.)

“Our findings suggest that high intake of supplemental calcium is associated with an excess risk of CVD death in men but not in women. Additional studies are needed to investigate the effect of supplemental calcium use beyond bone health,” researchers concluded.

Taylor Wallace, PhD, CRN’s senior director, scientific and regulatory affairs, argued, “[T]his study proves inconsistent with a recent wave of new research that concludes that calcium supplementation is beneficial to bone health and also poses no risk to cardiovascular health.”

Wallace pointed to three recent studies in particular showing a benefit from calcium. One is a February 2013 Osteoporosis International study (RL Prentice et al.) that found that calcium and vitamin D supplementation reduced risk of hip fracture in postmenopausal women. Another, published in Advances in Nutrition in November 2012, concluded that calcium supplements can help individuals who don’t receive enough calcium through dietary sources to achieve optimal bone health.

Finally, Wallace pointed to an American Journal of Clinical Nutrition study from December 2012 (EJ Samelson et al.) that concluded that high calcium intake does not increase coronary artery calcification. Wallace said this study gives more convincing evidence compared to the JAMA study because unlike the JAMA study, it was specifically designed to look at CVD outcomes and had more frequent follow-up. By contrast, he said, the AARP Diet and Health Study was designed to investigate the relationship between diet and cancer, not to measure CVD outcomes.          

Wallace also critiqued another February study published in the British Medical Journal, “Long term calcium intake and rates of all cause and cardiovascular mortality: community based prospective longitudinal cohort study” (K Michaëlsson et al.). The prospective longitudinal cohort study, which investigated the association between long-term intake of dietary and supplemental calcium and death from all causes and cardiovascular disease, concluded, “High intakes of calcium in women are associated with higher death rates from all causes and cardiovascular disease but not from stroke.” The study involved a Swedish population-based cohort established in 1987–1990 of 61,433 female subjects who were followed for a median of 19 years.

According to Wallace, “[T]his study did not demonstrate a cause-and-effect relationship between calcium and heart health or all-cause mortality, and in fact, we are not aware of a single human study that dose. There are some very specific flaws in this study, beginning with the fact that it was not set up to address the question it answered. Further, it did not adjust for the role of hormone replacement therapy (HRT), and since science has gone back and forth as to whether HRT helps or hurts the heart, the jury is out as to how this might influence the findings.”