Comparison of two diets for the prevention of recurrent stones in idiopathic hypercalciuria.
BACKGROUND
A low-calcium diet is recommended to prevent recurrent stones in patients with idiopathic hypercalciuria, yet long-term data on the efficacy of a low-calcium diet are lacking. Recently, the efficacy of a low-calcium diet has been questioned, and greater emphasis has been placed on reducing the intake of animal protein and salt, but again, long-term data are unavailable.


METHODS
We conducted a five-year randomized trial comparing the effect of two diets in 120 men with recurrent calcium oxalate stones and hypercalciuria. Sixty men were assigned to a diet containing a normal amount of calcium (30 mmol per day) but reduced amounts of animal protein (52 g per day) and salt (50 mmol of sodium chloride per day); the other 60 men were assigned to the traditional low-calcium diet, which contained 10 mmol of calcium per day.


RESULTS
At five years, 12 of the 60 men on the normal-calcium, low-animal-protein, low-salt diet and 23 of the 60 men on the low-calcium diet had had relapses. The unadjusted relative risk of a recurrence for the group on the first diet, as compared with the group on the second diet, was 0.49 (95 percent confidence interval, 0.24 to 0.98; P=0.04). During follow-up, urinary calcium levels dropped significantly in both groups by approximately 170 mg per day (4.2 mmol per day). However, urinary oxalate excretion increased in the men on the low-calcium diet (by an average of 5.4 mg per day [60 micromol per day]) but decreased in those on the normal-calcium, low-animal-protein, low-salt diet (by an average of 7.2 mg per day [80 micromol per day]).


CONCLUSIONS
In men with recurrent calcium oxalate stones and hypercalciuria, restricted intake of animal protein and salt, combined with a normal calcium intake, provides greater protection than the traditional low-calcium diet.
Borghi
Loris
L
Department of Clinical Sciences, University of Parma, Parma, Italy. loris.borghi@unipr.it
Schianchi
Tania
T
Meschi
Tiziana
T
Guerra
Angela
A
Allegri
Franca
F
Maggiore
Umberto
U
Novarini
Almerico
A
D000328:Adult; D002118:Calcium / Q000652:urine*; D002129:Calcium Oxalate / Q000652:urine; D002136:Calcium, Dietary / Q000008:administration & dosage*; D004035:Diet Therapy; D004039:Diet, Sodium-Restricted; D004044:Dietary Proteins / Q000008:administration & dosage*; D006801:Humans; D015994:Incidence; D007669:Kidney Calculi / Q000209:etiology / Q000517:prevention & control*; D008297:Male; D008875:Middle Aged; D010070:Oxalates / Q000652:urine; D055502:Secondary Prevention
D002136:Calcium, Dietary; D004044:Dietary Proteins; D010070:Oxalates; D002129:Calcium Oxalate; D002118:Calcium