Calcium Supplements May Damage the Heart

18 Oct 2016 --- Researchers at Johns Hopkins Medicine have 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 is still protective. 

Motivated by previous studies looking at the effects of calcium on the heart and vascular system, the researchers state that the results of their study add to growing scientific concerns about the potential harms of supplements.

However, they also caution that the report, published in the Journal of the American Heart Association, only documents an association between calcium supplements and atherosclerosis, and does not prove cause and effect.

It’s thought that 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,” says Erin Michos, M.D., M.H.S., 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. 

Michos continued, “But our study adds to the body of evidence that excess calcium in the form of supplements may harm the heart and vascular system.” 

“Ingested calcium supplements 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,” says nutritionist John Anderson, Ph.D., professor emeritus of nutrition at the University of North Carolina at Chapel Hill’s Gillings School of Global Public Health and a co-author of the report. 

The study focused on 2,742 participants, aged from 45 to 84, who completed dietary questionnaires and two CT scans spanning 10 years apart. 

At the study’s onset in 2000, all participants answered a 120-part 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. Separately, the researchers inventoried what drugs and supplements each participant took on a daily basis. 

The investigators then used cardiac CT scans to measure participants’ coronary artery calcium scores, a measure of calcification in the heart’s arteries and a marker of heart disease risk when the score is above zero. 

Initially, 1,175 participants showed plaque in their heart arteries. The coronary artery calcium tests were repeated 10 years later to assess newly developing or worsening coronary heart disease. 

Lastly, the researchers split the participants into groups based on their total calcium intake, including both calcium supplements and dietary calcium. 

They found that the groups where participants had the highest total calcium intake, (greater than 1,400 milligrams of calcium a day) was found to be on average 27 percent less likely than the 20 percent of participants with the lowest calcium intake (less than 400 milligrams of daily calcium) to develop heart disease.

However, when the investigators focused on the differences among those taking in only dietary calcium and those using calcium supplements, they found differing results. 

Forty-six percent of their study population used calcium supplements, and the researchers 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,” says Anderson, adding, “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.” 

“Based on this evidence, 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,” says 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.”