High sodium chloride intake is associated with low bone density in calciumstone-forming patients

Background: Although renal stone disease has been associated with reduced b one mass, the impact of nutrient intake on bone loss is unknown. Subjects a nd methods: The present study was undertaken to investigate the influence o f nutrient intake on bone density of 85 calcium stone-forming (CSF) patient s (47 male and 38 premenopausal females) aged 41 +/- 11 years (X +/- SD). B one mineral density (BMD) was measured using dual energy X-ray absorptiomet ry at the lumbar spine (L-2 - L-4) and femoral neck sites: and low BMD was defined as a T score < -1 (WHO criteria). A 4-day dietary record and a 24-h our urine sample were obtained from each patient for the assessment of nutr ient intake and urinary calcium (Uc,), sodium (U-Na), phosphate and creatin ine excretion. Results: Forty-eight patients (56%) presented normal BMD and 37 (44%) low BMD. There were no statistical differences regarding age, wei ght, height, body mass index, protein, calcium and phosphorus intakes betwe en both groups. The mean Uc,, phosphorus and nitrogen appearance also did n ot differ between groups. However, there was a higher percentage of hyperca lciuria among low vs normal BMD patients (62 vs 33%, p < 0.05). Low BMD pat ients presented a higher mean sodium chloride (NaCl) intake and excretion ( UNa) than normal BMD (14 +/- 5 vs 12 +/- 4 g/day and 246 +/- 85 vs 204 +/- 68 mEq/day, respectively p < 0.05). The percentage of patients presenting N aCl intake greater than or equal to 16 g/day was also higher among low vs n ormal BMD patients (35 vs 12%, p < 0.05). After adjustment for calcium and protein intakes, age, weight, body mass index, urinary calcium, citrate and uric acid excretion, and duration of stone disease, multiple-regression an alysis showed that a high NaCl intake (2 16 g/day) was the single variable that was predictive of risk of low bone density in CSF patients (odds ratio = 3.8). Conclusion: These data suggest that reducing salt intake should be recommended for CSF patients presenting hypercalciuria and osteopenia.