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


METHODS
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).


CONCLUSIONS
A low-salt diet can reduce calcium excretion in hypercalciuric stone formers. This trial was registered at clinicaltrials.gov as NCT01005082.
Nouvenne
Antonio
A
Department of Clinical Sciences, University of Parma, Parma, Italy. antonio.nouvenne@alice.it
Meschi
Tiziana
T
Prati
Beatrice
B
Guerra
Angela
A
Allegri
Franca
F
Vezzoli
Giuseppe
G
Soldati
Laura
L
Gambaro
Giovanni
G
Maggiore
Umberto
U
Borghi
Loris
L
D000328:Adult; D002118:Calcium / Q000652:urine*; D002129:Calcium Oxalate / Q000378:metabolism*; D004039:Diet, Sodium-Restricted; D005260:Female; D006801:Humans; D053565:Hypercalciuria / Q000178:diet therapy* / Q000652:urine; D007669:Kidney Calculi / Q000737:chemistry / Q000178:diet therapy* / Q000652:urine; D008297:Male; D008875:Middle Aged; D012964:Sodium / Q000652:urine*; D017673:Sodium Chloride, Dietary / Q000652:urine*; D014867:Water
D017673:Sodium Chloride, Dietary; D014867:Water; D002129:Calcium Oxalate; D012964:Sodium; D002118:Calcium