Debate Continues on Kidney Stones and Calcium Supplements

Another study continues the debate over calcium supplements and kidney stone risk-this time at the Endocrine Society’s Annual Meeting in Houston.

Funded by the National Institute on Aging, the yearlong study assigned 163 postmenopausal women to a daily dose of vitamin D (dosages ranging from 400 and 4800 IU) or placebo. Participants were also assigned to 691 mg of calcium daily-a dose later increased to 1200 or 1400 mg daily. Blood and urinary levels of calcium were measured at baseline and every three months.

The researchers, led by J Christopher Gallagher, MD, of Creighton University Medical Center (Omaha, NE), concluded that 33% of participants had high urinary calcium (hypercalciuria) and 10% had high blood calcium (hypercalcemia) at some point during the study.

In light of previously published research, which often associates the two conditions with increased kidney stone risk, the research team concluded that its study adds more evidence to the potential link. The headline of their official press release suggests as much.

“The use of calcium and vitamin D supplementation may not be as benign as previously thought,” adds Gallagher.

Yet the conclusion, as it pertains to this study, seems an overreaction. No kidney stones were documented during the course of the study, and the researchers said “it is not clear whether it is the extra calcium, the vitamin D, or both together that cause [hypercalciuria or hypercalcemia].”

Gallagher noted that monitoring of blood and urine calcium levels is warranted for those who use these supplements on a long-term basis-something that he says is rarely done in clinical practice.

The study is pending publication in a peer-reviewed journal.