Calcium Citrate May Not Cause Kidney Stones

DALLAS--Calcium citrate supplementation alone or in combination with potassium citrate does not increase the risk of kidney stones in healthy postmenopausal women, according to a study published in the September issue of The Journal of Urology (172, 3:958-61, 2004) (www.jurology.com).

In the randomized clinical trial of four two-week phases, 18 postmenopausal women without stones received twice-daily supplementation with 400 mg calcium citrate, 20 mEq potassium citrate, calcium citrate and potassium citrate (at same doses) or placebo. During the last two days of each phase, urine samples were obtained in 24-hour pools and analyzed for stone risk. Compared to placebo, calcium citrate increased urinary calcium and citrate, decreased urinary oxalate and phosphate and did not affect urinary saturation of calcium oxalate, brushite and undissociated uric acid.

Potassium citrate decreased urinary calcium, increased urinary citrate and pH, decreased urinary saturation of calcium oxalate and undissociated uric acid, and did not change the saturation of brushite. When calcium citrate was combined with potassium citrate, urinary pH increased, saturation of brushite increased, levels of urinary undissociated uric acid decreased, levels of urinary calcium remained elevated, urinary citrate levels increased, and urinary oxalate levels decreased, thereby slightly decreasing the urinary saturation of calcium oxalate.

The researchers concluded calcium citrate supplementation does not increase the risk of stone formation in healthy postmenopausal women, and the co-administered potassium citrate may provide additional protection against formation of uric acid and calcium oxalate stones.