Effect of calcium citrate supplementation on urinary calcium oxalate saturation in female stone formers: implications for prevention of osteoporosis

In 14 women aged 37–68 y with a history of renal calcium calculi, bone densities were 12.0% below those of age-matched control subjects at the L2-4 lumbar spine (P = 0.007) and 6.4% less at the femoral neck (P = 0.095). A low-oxalate diet was supplemented with 1 g Ca/d as citrate. In 6 mo, plasma l,25(OH)2D concentrations fell from 53.2 ± 18.8 to 41.9 ± 15.2 ng/L (P = 0.02) and parathyroid hormone from 39.1 ± 17.0 to 30.8 ± 12.5 ng/L (P = 0.02). Calcium oxalate saturation was 2.15 ± 1.38 at baseline, 2.27 ± 1.00 at 1 mo, and 2.06 ± 1.57 at 6 mo. The increase in urinary calcium at 1 mo from 4.411 ± 1.87 to 6.514 ± 2.82 mmol/24 h(P = 0.01) was offset by a parallel increase in citrate excretion from 2.909 ± 1.45 to 3.455 ± 1.34 mmol/24 h (P = 0.03). Calcium citrate supplementation did not increase the lithogenicity of the women in this protocol.