Patients who took calcium increased their risk of a heart attack by about 30 percent, according to researchers who said the use of dietary supplements for preventing and treating osteoporosis should be reviewed.
In five studies with more than 8,000 patients, half of whom were on calcium, the supplement users had 143 heart attacks during the research compared with 111 for people on placebo, scientists from New Zealand, the U.K. and the U.S. wrote today in the British Medical Journal. The risk was greatest when calcium intake from food was above average, regardless of patients’ age or sex, according to the analysis.
Calcium supplements are prescribed to reduce the risk of fractures and to prevent and treat osteoporosis, a thinning of the bones. Previous studies had found no increased risk of heart attacks with higher calcium intake from food. The analysis suggests that the extra hazard is associated with supplements, the medical journal said in an e-mailed statement.
“For patients who are at risk of heart disease and also suffering from osteoporosis, perhaps calcium supplementation should not be recommended,” Suzanne Steinbaum, director of women and heart disease at the Heart & Vascular Institute of Lenox Hill Hospital in New York and a spokeswoman for the Dallas-based American Heart Association, said in a telephone interview.
Steinbaum wasn’t involved in the analysis, whose lead author is Mark Bolland, a senior research fellow in the Department of Medicine at the University of Auckland, in New Zealand.
The researchers also found a link between the calcium supplements and a higher chance of stroke or sudden death, though they said those results weren’t statistically significant.
The analysis covered data from 11 trials, involving a total of almost 12,000 participants over age 40 on average, about half of whom were taking calcium supplements. For five of the trials, data were available on whether the patients had suffered heart attacks.
Calcium is the most prevalent mineral in the body and is found in dairy products and some green vegetables. The human body uses the mineral to strengthen its skeleton, storing 99 percent of calcium in the bones and teeth.
The recommended daily calcium allowance in the U.K. is 1,300 milligrams for adults, according to the London-based Food Standards Agency. Deficiencies are common in adults when the process of bone breakdown starts to occur more often than bone formation. Bone density can weaken, leading to osteoporosis.
“Patients with osteoporosis should generally not be treated with calcium supplements, either alone or combined with vitamin D, unless they are also receiving an effective treatment for osteoporosis for a recognized indication,” John Cleland, a professor of cardiology at the University of Hull in the U.K., and colleagues wrote in an editorial published along with the analysis.
The researchers said they excluded from their analysis studies that compared coadministered calcium and vitamin D supplements with placebo. The findings may not be applicable to those supplements, the authors wrote.
Osteoporosis affects an estimated 10 million Americans, according to the Washington-based National Osteoporosis Foundation. About 3 million people in the U.K. also have the condition, according to National Osteoporosis Society, based in Camerton, near Bath, England.