Calcium oxalate nephrolithiasis is influenced by a number of genetic and environmental factors. In the study reviewed below, Borghi and colleagues focused on an important environmental factor, diet, in an effort to reduce stone activity in hypercalciuric, recurrent, calcium oxalate stone formers.
Comparison of Two Diets for the Prevention of Recurrent Stones in Idiopathic Hypercalciuria
Borghi L, Schianchi T, Meschi T, et al.
N Engl J Med. 2002;346:77–8411784873.
In this 5-year study, subjects were randomized to a low-calcium diet, or a normal-calcium, low-sodium, and low-animal- protein diet. Sixty patients were enrolled in each arm of the study, and a similar proportion (10%) withdrew during the course of the study for various reasons. At the conclusion of the study, the relative risk of stone recurrence in the normal-calcium, low-sodium, and low-animal-protein diet cohort as compared with the low-calcium diet group was 0.49 (P = .04). Calcium excretion significantly decreased in both groups, whereas oxalate excretion increased in the low-calcium diet subjects but decreased in those on the normal-calcium, low-sodium, and low-animal-protein diet. Dietary compliance was excellent in both groups. The relative supersaturation of calcium oxalate decreased significantly from baseline in both groups; however, this was more prominent in the normal-calcium, low-sodium, and low-animal-protein diet group. Subjects with a history of more intense stone activity prior to randomization had diminished risk reduction as compared with those with fewer lead-in stone events.
Commentary
There were a few weaknesses in this landmark study. The normal-calcium, low-sodium, and low-animal-protein dietary protocol was more tightly regulated. The authors did not provide data on citrate, phosphorus, and uric acid excretion. They also did not analyze differences in the urinary variables between those who had a recurrence and those who did not.
The following are take-home messages from this study: 1) an initial trial of a normal-calcium, low-sodium, and low-animal-protein diet should be considered in recurrent, hypercalciuric calcium oxalate stone formers with moderate stone activity; 2) dietary calcium restriction should be avoided in the majority of stone formers, which has also been demonstrated in the studies of Curhan and associates1,2; and 3) patients with more pronounced stone activity may require other measures to attenuate recurrent stone events, such as medical therapy.
References
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