Kidney patients who take calcium to lower phosphorous levels at higher risk of death: Study

Women's College HospitalJul 20 2013

Kidney patients who take calcium supplements to lower their phosphorous levels may be at a 22 per cent higher risk of death than those who take other non-calcium based treatments, according to a new study by Women's College Hospital's Dr. Sophie Jamal.

The study, published today in the Lancet, calls into question the long-time practice of prescribing calcium to lower phosphate levels in patients with chronic kidney disease. The researchers suggest some of the calcium is absorbed into the blood stream and may expedite hardening of the arteries, leading to a higher risk of heart disease and even death. Cardiovascular disease is a leading cause of death for people with chronic kidney disease.

"Doctors commonly prescribe calcium supplements to prevent elevated phosphate levels, which can damage the body, but a growing number of studies have shown calcium supplements may actually increase the risk of heart disease," explains Dr. Sophie Jamal, a physician at Women's College Hospital and an associate professor of medicine at the University of Toronto. "Our study validates these claims and, for the first time, shows the long-term consequences of taking calcium supplements can be dangerous for patients with kidney disease."

As part of their analysis, researchers reviewed 11 randomized, controlled studies that included more than 4,600 patients. The researchers assessed the risk of heart disease, including heart attack, stroke, and hardening of the arteries, along with death among individuals prescribed the medication containing calcium and those prescribed the medication without calcium. They found:

• A 22% reduction in death among patients who took non-calcium based treatments sevelamer and lanthanum.
• Less artery calcification (hardening) in patients who did not take calcium supplements.

"Some researchers and physicians have been saying for years that kidney disease patients need to get off calcium, now we think our review shows there is much more solid evidence to argue for that change to clinical practice," the study's senior author Ross Tsuyuki from the University of Alberta's faculty of medicine and dentistry.

In the meantime, given the study's findings, the researchers suggest non-calcium containing treatments be used as a first line of treatment to lower phosphate for patients with chronic kidney disease.

"The findings of our study provides the best evidence as to what doctors should be prescribing their patients, but further research is necessary to help us understand how exactly calcium increases the risk of death, if non calcium-based treatments reduce the risk of death, and whether certain types of treatments may be more effective and beneficial than others," says Dr. Jamal.