Dr. Baron was surprised by the findings. “Calcium supplements have been widely used for quite a while,” he says. “Other studies have suggested, if anything, that [calcium] might have a protective effect.”
The findings do not imply that people should reduce the amount of calcium in their diet, Dr. Hayes stresses. Calcium is found in vegetables, fortified cereal, and dairy products such as milk and yogurt, which are an important source of vitamin D in addition to calcium.
“Calcium isn’t bad,” she says.
John Cleland, MD, a cardiologist at Hull York Medical School, in the U.K., says that calcium supplements are helpful for “very few” patients.
They may be beneficial for some children, some pregnant women, and people with proven calcium deficiency (a relatively rare condition), says Dr. Cleland, who co-authored an editorial accompanying the study. But, he adds, “there’s no evidence for use in older people” who do not have calcium deficiencies.
Doctors should not recommend calcium supplements for patients with osteoporosis unless the patients are also taking an effective osteoporosis treatment, Dr. Cleland and his co-author conclude.
It’s unclear how calcium supplements might increase heart attack risk. They may contribute to the hardening of arteries (atherosclerosis) by increasing calcium levels in the blood, or they may cause changes to blood flow. Hormone responses caused by calcium may also be involved, the study notes.
The study leaves several unanswered questions for future research. The researchers only included patients who were taking calcium supplements but not vitamin D supplements, for instance. That combination—often found in a single pill—is common and may have a different effect than calcium alone on heart risk, as vitamin D is believed to promote heart health.
