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 to be protective, scientists have found.
After analysing 10 years of medical tests on more than 2,700 people, researchers at Johns Hopkins University School of Medicine in the US, said the results add to growing scientific concerns about the potential harms of supplement.
“Our study adds to the body of evidence that excess calcium in the form of supplements may harm the heart and vascular system,” said Erin Michos, from Johns Hopkins Medicine.
Previous studies have shown that “ingested calcium supplements – particularly in older people – do not 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, from University of North Carolina in the US.
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.
The study focused on 2,742 of these participants who completed dietary questionnaires and two CT scans spanning 10 years apart. The participants chosen for this study ranged in age from 45 to 84, and 51 per cent were female.
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 and calcium-enriched foods such as cereals.
For the analysis, the researchers first split the participants into five groups based on their total calcium
intake, including both calcium supplements and dietary calcium.
After adjusting the data for age, sex, race, exercise, smoking, income, education, weight, smoking, drinking, blood pressure, blood sugar and family medical history, researchers separated out 20 per cent of participants with the highest total calcium intake, which was greater than 1,400 milligrammes of calcium a day.
That group was found to be on average 27 per cent less likely than the 20 per cent of participants with the lowest calcium intake – less than 400 milligrammes of daily calcium – to develop heart disease, as indicated by their coronary artery calcium test.
The research was published in the Journal of the American Heart Association.