Dietary Interventions for Recurrent Calcium Oxalate Nephrolithiasis: A Systematic Review of Randomized Trials

Abstract

Introduction: Dietary modification is a cornerstone of stone prevention, but evidence for specific interventions is inconsistent. This review focuses on RCTs of dietary interventions for recurrent calcium oxalate stones.

Methods: We searched CENTRAL, clinicaltrials.gov, and Embase (1990–2024) for RCTs in adults with ≥2 calcium oxalate stones. Interventions: fluid intake, low-sodium diet, calcium restriction, oxalate restriction, or DASH diet. Primary outcome: stone recurrence (radiographic or clinical). Meta-analysis performed where possible.

Results: Twelve RCTs (n=2,416) were identified. Increased fluid intake to achieve ≥2.5 L urine/day reduced recurrence by 55% (RR 0.45, 95%CI 0.32–0.64). Low-sodium diet (≤2 g/day) reduced recurrence (RR 0.55) in one large trial. Calcium restriction was harmful (RR 1.85, p<0.01). Oxalate restriction alone had no effect (RR 0.92). The DASH diet (low in sodium, high in fruits/vegetables) reduced recurrence in a single RCT (RR 0.49).

Discussion: High fluid and low sodium intakes have the strongest evidence. Calcium restriction is obsolete; dietary calcium binds oxalate in gut. Most trials had high attrition, and dietary adherence was poorly measured.

Conclusions: For recurrent calcium oxalate stones, recommend at least 2.5 L fluid daily, sodium <2 g/day, and normal calcium intake (1,000–1,200 mg/day). The DASH diet is a promising comprehensive approach.