A randomized trial of low-animal-protein or high-fiber diets for secondary prevention of calcium nephrolithiasis

Background: The purpose of this trial was to evaluate the efficacy of a low-animal-protein diet (LAPD) or a high-fiber diet (HFD) for the prevention of calcium nephrolithiasis recurrence. Methods: We conducted a 4-year randomized trial comparing the effect of 2 diets in 175 idiopathic calcium stone formers. Fifty-five were assigned to a LAPD (25 g/day fiber) and 60 were placed on a normal diet (control group). The primary outcome measure was the time to the first recurrence of calcium nephrolithiasis. Daily urine compositions were analyzed at baseline, at month 4 (M4), M12, M24, M36 and M48. Results: Seventy-three patients completed the trial (23 in the LAPD group, 27 in the HFD group and 23 in the control group). Recurrence was 48% (11/23) in the LAPD group, 63% (17/27) in the HFD group and 48% (11/23) in the control group (p = not significant). During follow-up, urinary calcium levels and other urine parameters did not change significantly in the 3 groups, except for a significant decrease in 24-hour urinary sulfate in the LAPD group. Conclusions: In idiopathic calcium stone formers, neither a LAPD nor a HFD appeared to provide protection against recurrence.