Calcium Supplements May Damage Heart
After analyzing 10 years of medical tests on more than 2,700 people, researchers at Johns Hopkins Medicine and elsewhere concluded that taking calcium in the form of supplements may raise the risk of plaque buildup in arteries and heart damage, although a diet high in calcium-rich foods appears be protective.
In a report on the research published Oct. 10 in the Journal of the American Heart Association, researchers caution that their work only documents an association between calcium supplements and atherosclerosis, and does not prove cause and effect. But they said the results add to growing scientific concerns about the potential harm of supplements, and they urged consultation with a physician before using calcium supplements. An estimated 43 percent of American adult men and women take a supplement that includes calcium, according the National Institutes of Health.
“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,” said Dr. Erin Michos, 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. “But our study adds to the body of evidence that excess calcium in the form of supplements may harm the heart and vascular system.”
The researchers looked at the effects of calcium on the heart and vascular system because studies already showed that “ingested calcium supplements — particularly in older people — don’t make it to the skeleton or get completely excreted in the urine, so they must be accumulating in the body’s soft tissues,” said nutritionist John Anderson, professor emeritus of nutrition at the University of North Carolina at Chapel Hill and co-author. Scientists also knew that as a person ages, calcium-based plaque builds up in the body’s main blood vessel, the aorta and other arteries, impeding blood flow and increasing the risk of heart attack.
The researchers looked at detailed information from the Multi-Ethnic Study of Atherosclerosis, a long-running research project, which included more than 6,000 people seen at six universities, including Johns Hopkins. Their study focused on 2,742 of these participants who completed dietary questionnaires and two CT scans 10 years apart.
At the start of the study in 2000, all participants answered a questionnaire about their dietary habits to determine how much calcium they took in by eating dairy products, leafy greens, calcium-enriched foods like cereals and other calcium-rich foods. The researchers also inventoried what drugs and supplements each participant took daily. Cardiac CT scans measured the calcium in participants’ heart arteries. Initially, 1,175 participants showed plaque in their heart arteries. The tests were repeated 10 years later to assess newly developing or worsening coronary heart disease.
Researchers focused on the differences among those taking in only dietary calcium and the 46 percent using supplements. They found that supplement users showed a 22 percent increased likelihood of having their coronary artery calcium scores rise higher than zero over the decade, indicating development of heart disease.
“There is clearly something different in how the body uses and responds to supplements versus intake through diet that makes it riskier,” said Anderson. “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.”
Among participants with highest dietary intake of calcium — over 1,022 milligrams per day — there was no increase in developing heart disease over the 10-year study period.
“Based on this evidence, we can tell 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,” said Michos. “But 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.”
More than half of women over 60 take calcium supplements because they believe it will reduce their risk of osteoporosis.
Article by Johns Hopkins Medicine