Calcium Supplements May Increase Risk for Incident Coronary Artery Calcification

High total calcium intake was associated with a decreased risk of incident atherosclerosis over long-term follow-up, particularly if achieved without supplement use; however, calcium supplement use may increase the risk for incident coronary artery calcification (CAC), according to a new study.

“When placing our findings in context with prior studies, this growing body of literature does suggests that calcium loading from supplements may not be free of undesirable side effects, and that patients should really discuss with their doctors whether they should be taking them or not,” said study author Erin D. Michos, MD, MHS, FACC, FAHA, associate director of preventive cardiology and associate professor of medicine at the Ciccarone Center for the Prevention of Heart Disease at the Johns Hopkins University School of Medicine, Baltimore.
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The researchers evaluated 2742 individuals who filled out a dietary questionnaire and medication inventory at baseline and underwent 2 cardiac CTs obtained 10-years apart. Their analysis primarily focused on the 1567 subjects with CAC scores of 0 (suggesting no apparent atherosclerosis) at baseline. They found that even after adjusting for the known traditional risk factors for atherosclerosis, including age, sex, race, hypertension, diabetes, lipids, smoking, and lack of physical activity, as well as total calories consumed, the use of calcium supplements was independently associated with a 22% risk of incident development of CAC on their repeat scans 10 years later.

The highest quintile of total calcium intake did seem to be inversely associated with incident CAC suggesting a protective effect on atherosclerosis, but this inverse association was largely driven among the non-supplement users. When the researchers looked at dietary calcium alone, they did not find any excess risk of CAC for high dietary calcium.

“Our study was observational, so although we carefully adjusted for numerous clinical characteristics, there still may be residual confounding,” Dr Michos noted. “Individuals who take supplements may be very different than non-supplement users. Similarly, individuals who intake a diet high in calcium rich foods may be doing other health-promoting activities.”

It’s important to remind primary care physicians that prior meta-analyses of randomized clinical trials have found data for calcium supplements (with or without vitamin D) is only weak and inconsistent reduction in fractures, she said.

“In fact, the US Preventive Services Task Force concluded there was insufficient evidence to either support—or recommend against—the use of calcium for fracture prevention,” Dr Michos said. “Therefore, calcium supplements should generally not be recommended for fracture prevention among most US adults, although there might be a role in special populations with very low calcium intake. Patients at risk for osteoporosis and fracture may benefit from other medications like bisphosphonates for prevention instead.”

—Mike Bederka

Reference:

Anderson JJ, Kruszka B, Delaney JA, et al. Calcium intake from diet and supplements and the risk of coronary artery calcification and its progression among older adults: 10-year follow-up of the multi-ethnic study of atherosclerosis (MESA) [published online October 11, 2016]. J Am Heart Assoc. doi: 10.1161/JAHA.116.003815.