Kidney disease & calcium: Supplements may increase mortality risk

Physicians may think twice before prescribing calcium supplements to patients with chronic kidney disease, based on results of a study published online July 19 in The Lancet. Researchers reported that the use of calcium-free phosphate binders may lower mortality risk in these patients compared with calcium-based binders.

In a meta-analysis, Sophie A. Jamal, MD, PhD, of Women’s College Hospital Research Institute in Toronto, and her colleagues examined data from 11 randomized trials that included 4,622 patients.

They found a 22 percent lower all-cause mortality risk among patients who used supplements that did not contain calcium, which may raise questions about common treatments for hyperphosphatemia.

“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,” Jamal said in a press release. “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.”

The analysis also revealed that patients who took supplements without calcium had less coronary artery calcification. The difference in arterial hardening could be the reason why noncalcium phosphate binders are linked to lower mortality.

“Progression of coronary artery calcification has been associated with an increase in vascular stiffness and QT dispersion on the surface electrocardiogram, regarded as a marker of increased risk of ventricular arrhythmias,” the authors wrote.

It was not clear whether the higher risk of dying was related to cardiovascular events, since this outcome was not reported in the studies.

They also noted a lower, though not statistically significant, mortality risk among patients who used either sevelamer or lanthanum compared with patients who used calcium-based supplements.

While the authors argued that the studies included in their analysis were of sufficient quality, they added that research is needed to learn more about mortality patterns and whether certain treatments may be better options for patients.

Even though the effects of calcium-based binders are still unclear, the authors suggested using noncalcium containing phosphate binders as standard treatment, given their findings.

“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,” co-author Ross Tsuyuki, PharmD, said in a release.