By Steven Reinberg
Both men and women take calcium supplements to prevent bone loss. In this study of calcium intake, the risk of dying from heart disease was higher for men but not for women.
"Increasing evidence indicates that too much supplemental calcium might increase the risk of cardiovascular disease," said Susanna Larsson, an associate professor at the Institute of Environmental Medicine at the Karolinska Institute, in Stockholm.
Larsson, who was not part of the study but wrote an accompanying journal editorial, added that "the paradigm 'the more the better' seems invalid for calcium supplementation."
The report was published in the Feb. 4 online edition of the journal JAMA Internal Medicine.
To find out if calcium supplements were associated with an increased risk of dying from cardiovascular disease, a team of scientists led by Qian Xiao, of the U.S. National Cancer Institute, collected data on more than 388,000 men and women, aged 50 to 71 years old. They took part in a study on diet and health conducted by the U.S. National Institutes of Health and the AARP from 1995 to 1996.
Over an average 12 years of follow-up, about 7,900 men died from cardiovascular disease, as did nearly 4,000 women. Among those who died, 51 percent of men and 70 percent of women were taking calcium supplements, the researchers found.
Xiao's group calculated that men taking 1,000 milligrams a day of a calcium supplement had a 20 percent increased risk of dying from heart disease. Men also had a 14 percent increased risk of dying from a stroke, but this was not statistically significant, the researchers said.
Among women, however, calcium supplements were not linked to an increased risk of dying from cardiovascular disease. And, calcium from diet didn't increase the risk of dying from cardiovascular disease for either sex, the researchers found.
The study authors said more research is needed to determine whether there is difference between men and women in the cardiovascular effects of calcium supplements.
"Given the extensive use of calcium supplements in the population[often for osteoporosis], it is of great importance to assess the effect of supplemental calcium use beyond bone health," the investigators concluded in the study.
Taylor Wallace, a representative of the supplement industry, faulted this and other studies because, he said, they were not specifically meant to address calcium supplements and heart disease.
Wallace, who is senior director for Scientific & Regulatory Affairs at the Council for Responsible Nutrition, said most studies of calcium supplements show no effects on the heart.
"Calcium supplements probably have a null effect on the cardiovascular system," he said.
Wallace noted that in the new study, the data that researchers used to draw their conclusions looked at diet and the risk for cancer, not whether calcium supplements were bad for the heart.
"What is needed, to close the chapter on this, is a large randomized control trial that is specifically designed to look at cardiovascular disease and calcium supplements," he said.
Although the study tied supplement use to increased risk of death from heart disease in men, it didn't establish a cause-and-effect relationship.
One medical expert said that neither men nor women should be taking calcium supplements without first checking with their doctor to assess the risks and benefits of these supplements.
"While further studies are needed, calcium supplements should be used only after careful consideration of whether the potential benefits in terms of bone health outweigh the potential cardiovascular risks," said Dr. Gregg Fonarow, a spokesman for the American Heart Association and a professor of cardiology at the University of California, Los Angeles.
To learn more about calcium supplements, visit the U.S. Office of Dietary Supplements.