Taking calcium supplements may be bad news for your heart, according to a new study conducted by researchers from Johns Hopkins Medicine and elsewhere.
While a calcium-rich diet could actually benefit the heart, the study found that taking calcium in supplement form seems to increase the risk of plaque buildup in arteries and heart damage.
The researchers published their findings this week in The Journal of the American Heart Association, based on 10 years of medical research tests. The findings add to growing scientific concerns about the potential harm of supplements.
An estimated 43 percent of American adult men and women take a supplement that includes calcium, according to the National Institutes of Health. And more than half of women over 60 take calcium supplements—many without a doctor's oversight—because they believe it will reduce their risk of osteoporosis.
"Patients should really discuss any plan to take calcium supplements with their doctor to sort out a proper dosage or whether they even need them," says Erin Michos, associate professor at the Ciccarone Center for the Prevention of Heart Disease at Johns Hopkins Medicine.
While the scientists saw an association between calcium supplements and atherosclerosis—the hardening and narrowing of the arteries that can cause cardiovascular disease—they note that their research hasn't proven cause and effect.
"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," says nutritionist John Anderson, a professor at the University of North Carolina at Chapel Hill.
Past studies have shown that calcium supplements can accumulate in the body's soft tissue, rather than making it to the skeleton or being completely excreted in urine. That risk is higher with older people, who also face increased risk of heart attacks as calcium-based plaque builds up in the arteries.
The new research found that calcium supplement users were 22 percent more likely to see their coronary artery calcium scores rise over the 10-year study period. Meanwhile, participants who ingested calcium through their normal diets—even at the highest doses—saw no increased risk of heart disease.
"We can tell our patients that there doesn't seem to be any harm in eating a heart-healthy diet that includes calcium-rich foods, and it may even be beneficial for the heart," Michos says.
The study focused on over 2,700 participants in a research project funded by the National Heart, Lung, and Blood Institute, who completed dietary questionnaires and two CT scans 10 years apart. The researchers accounted for various demographic and lifestyle factors that could influence the participants' risk of heart disease.Read more from Hopkins Medicine