Effects of a low-salt diet on idiopathic hypercalciuria in calcium-oxalate stone formers: a 3-mo randomized controlled trial

• Published in: The American journal of clinical nutrition 2010-03, Vol.91 (3), p.565-570
• Main Authors: Nouvenne, Antonio, Meschi, Tiziana, Prati, Beatrice, Guerra, Angela, Allegri, Franca, Vezzoli, Giuseppe, Soldati, Laura, Gambaro, Giovanni, Maggiore, Umberto, Borghi, Loris
• Format: Article
• Language: English
• Subjects: Adult; Biological and medical sciences; Calcium; Calcium - urine; calcium oxalate; Calcium Oxalate - metabolism; Clinical trials; Diet; Diet, Sodium-Restricted; excretion; Feeding. Feeding behavior; Female; Fundamental and applied biological sciences. Psychology; Humans; Hypercalciuria - diet therapy; Hypercalciuria - urine; idiopathic hypercalciuria; Kidney Calculi - chemistry; Kidney Calculi - diet therapy; Kidney Calculi - urine; low sodium diet; Male; men; Middle Aged; patients; randomized clinical trials; renal calculi; Risk factors; Salt; sodium; Sodium - urine; Sodium Chloride, Dietary - urine; Therapy; Urine; Vertebrates: anatomy and physiology, studies on body, several organs or systems; Water; women
• ISSN: 0002-9165; 1938-3207
• DOI: 10.3945/ajcn.2009.28614

BACKGROUND: A direct relation exists between sodium and calcium excretion, but randomized studies evaluating the sustained effect of a low-salt diet on idiopathic hypercalciuria, one of the main risk factors for calcium-oxalate stone formation, are still lacking. OBJECTIVE: Our goal was to evaluate the effect of a low-salt diet on urinary calcium excretion in patients affected by idiopathic calcium nephrolithiasis. DESIGN: Patients affected by idiopathic calcium stone disease and hypercalciuria (>300 mg Ca/d in men and >250 mg Ca/d in women) were randomly assigned to receive either water therapy alone (control diet) or water therapy and a low-salt diet (low-sodium diet) for 3 mo. Twenty-four-hour urine samples were obtained twice from all patients: one sample at baseline on a free diet and one sample after 3 mo of treatment. RESULTS: A total of 210 patients were randomly assigned to receive a control diet (n = 102) or a low-sodium diet (n = 108); 13 patients (2 on the control diet, 11 on the low-sodium diet) withdrew from the trial. At the follow-up visit, patients on the low-sodium diet had lower urinary sodium (mean ± SD: 68 ± 43 mmol/d at 3 mo compared with 228 ± 57 mmol/d at baseline; P < 0.001). Concomitant with this change, they showed lower urinary calcium (271 ± 86 mg/d at 3 mo compared with 361 ± 129 mg/d on the control diet, P < 0.001) and lower oxalate excretion (28 ± 8 mg/d at 3 mo compared with 32 ± 10 mg/d on the control diet, P = 0.001). Urinary calcium was within the normal range in 61.9% of the patients on the low-salt diet and in 34.0% of those on the control diet (difference: +27.9%; 95% CI: +14.4%, +41.3%; P < 0.001). CONCLUSION: A low-salt diet can reduce calcium excretion in hypercalciuric stone formers. This trial was registered at clinicaltrials.gov as NCT01005082.