Baltimore—Based on a new study, pharmacists have some valuable advice to share: Taking too many calcium supplements appears to raise the risk of plaque buildup in arteries, which can damage the heart.

The report, published in the Journal of the American Heart Association, finds that the issue is not just too much of a good thing, but also how the calcium is ingested, especially for older users.

Johns Hopkins Medicine researchers and colleagues analyzed a decade of medical tests on more than 2,700 patients and concluded that taking calcium in the form of supplements might raise the risk of atherosclerosis and potential heart damage, but that a diet high in calcium-rich foods appears be protective.

“When it comes to using vitamin and mineral supplements, particularly calcium supplements being taken for bone health, many Americans think that more is always better,” explained corresponding author Erin Michos, MD, MHS, of the Johns Hopkins University School of Medicine. “But our study adds to the body of evidence that excess calcium in the form of supplements may harm the heart and vascular system.”

Background information in the article notes that about 43% of American adult men and women take a supplement that includes calcium.

For the study, researchers analyzed detailed information from the Multi-Ethnic Study of Atherosclerosis, a long-term research project funded by the National Heart, Lung, and Blood Institute, which included more than 6,000 people seen at 6 research universities, including Johns Hopkins. Their study focused on 2,742 of these participants who completed dietary questionnaires and two CT scans 10 years apart.

Participants—51% female, ranging in age from 45 to 84, and 41% white, 26% African-American, 22% Hispanic, and 12% Chinese—answered a 120-part questionnaire about their dietary habits at the study’s onset in 2000. Questions sought to determine how much calcium they ingested by eating dairy products, while at the same time researchers documented drugs and supplements each participant took on a daily basis.

Cardiac CT scans were employed to measure participants’ coronary artery calcium scores. With 1,175 participants initially showing plaque in their heart arteries, the coronary artery calcium tests were repeated 10 years later to assess newly developing or worsening coronary heart disease.

A group of 20% of participants with the highest total calcium intake, >1,400 mg daily, was found to be, on average, 27% less likely than the 20% of participants with the lowest calcium intake, defined as <400 mg daily, to develop heart disease. When just the 46% who used calcium supplements were considered, a 22% higher risk of having coronary artery calcium scores exceeding zero over the decade was identified.

Participants with highest dietary intake of calcium—over 1,022 mg per day—indicated no increase in relative risk of developing heart disease over the study period.

“There is clearly something different in how the body uses and responds to supplements versus intake through diet that makes it riskier,” co-author John Anderson, PhD, professor emeritus of nutrition at the University of North Carolina at Chapel Hill, pointed out. “It could be that supplements contain calcium salts, or it could be from taking a large dose all at once that the body is unable to process.”

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