Following a 10-year heart disease study that analyzed more than 2,700 people, researchers at John Hopkins Medicine in the United States and elsewhere say they are convinced that taking calcium in the form of supplements raises the risk of plaque buildup in arteries and cause heart damage. On the other hand, they point out that a diet high in calcium-rich foods appears to have a beneficial effect.
However, the researchers caution that their work only documents an association between calcium supplements and atherosclerosis, and does not prove cause and effect. But they add, their findings support growing scientific concerns about the potential harms of supplements.
Many people think that when it comes to taking vitamin and mineral supplements, more is often better but the new study proves that excess calcium in the form of supplements may in fact harm the heart and vascular system.
The researchers were motivated to look at the effects of calcium on the heart and vascular system because studies already showed that ingested calcium supplements — particularly in older people — do not make it to the skeleton or get completely excreted in the urine. 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.
"There is clearly something different in how the body uses and responds to supplements versus intake through diet that makes it riskier," say the study authors. "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."
The study also showed that among participants with highest dietary intake of calcium — over 1,022 milligrams per day — there was no increase in relative risk of developing heart disease over the 10-year study period.
Based on this evidence, it is clear that there is no harm in eating a heart-healthy diet that includes calcium-rich foods, and it may even be beneficial for the heart. 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.