Comparison of Two Diets for the Prevention of Recurrent Stones in Idiopathic Hypercalciuria

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The New England Journal of Medicine

Volume 346:77-84 January 10, 2002 Number 2

Comparison of Two Diets for the Prevention of Recurrent Stones in

Idiopathic Hypercalciuria

Loris Borghi, M.D., Tania Schianchi, M.D., Tiziana Meschi, M.D.,

Guerra, Ph.D., Franca Allegri, M.D., Umberto Maggiore, M.D., and

Almerico Novarini, M.D.

ABSTRACT

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 µmol 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 µmol 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.

Source Information

From the Departments of Clinical Sciences (L.B., T.S., T.M., A.G., F.A.,

A.N.) and Internal Medicine and Nephrology (U.M.), University of Parma,

Parma, Italy.

Address reprint requests to Dr. Borghi at the Department of Clinical

Sciences, University of Parma, Via Gramsci 14, 43100 Parma, Italy, or at

loris.borghi@....