Loris Borghi, M.D., Tania Schianchi, M.D., Tiziana Meschi, M.D., Angela Guerra, Ph.D., Franca Allegri, M.D., Umberto Maggiore, M.D., and Almerico Novarini, M.D. Comparison of Two Diets for the Prevention of Recurrent Stones in Idiopathic Hypercalciuria. N Engl J Med 2002; 346:77-84January 10, 2002DOI: 10.1056/NEJMoa010369
In this manuscript, 120 men with recurrent calcium oxalate stones and hypercalciuria were randomized to one of two diets:
NORMAL CALCIUM, REDUCED ANIMAL PROTEIN SALT DIET (DIET 1)normal calcium (30 mmol per day)
reduced animal protein (52 grams per day)
reduced salt intake (50 mmol sodium chloride daily)
LOW CALCIUM DIET (DIET 2)low calcium intake (10 mmol per day)
After 5 years of follow-up, only 12 of 60 men on Diet 1 had recurrent stones while 23 on Diet 2 had stones. The relative risk of stones in Diet 2 was therefore 0.49 (p=0.04). The increased rate of stone recurrence while on Diet 2 was most pronounced after 3 years. This "delayed effect" was due to the fact that most of the early recurrences occurred in patients at high-risk for stone formation (5 or more colic episodes in the year prior to randomization and/or 10 or more stones prior to randomization) regardless of the diet to which they were randomized.
|Borghi et al. NEJM, 2002.|
In addition, urinary calcium levels dropped in both groups. However, urinary oxalate levels increased dramatically in patients on Diet 2 - confirming the probable mechanism that a low-calcium diet promotes hyperoxaluria and increased stone formation.
Take home: Low-calcium diets do not prevent, and in fact increase, the risk of urinary calcium stone formation. A normal calcium diet with restricted animal protein and salt intake is the best diet to prevent recurrent stones in patients with hypercalciuria. Along with increased hydration, the diet validated by Borghi and colleagues is the basis for the dietary modifications most widely suggested to recurrent stone formers worldwide.
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