Urinary Lithogenic Risk Profile in Recurrent Stone Formers With Hyperoxaluria: A Randomized Controlled Trial Comparing DASH (Dietary Approaches to Stop Hypertension)-Style and Low-Oxalate Diets

Background: Patients with nephrolithiasis and hyperoxaluria generally are advised to follow a low-oxalate diet. However, most people do not eat isolated nutrients, but meals consisting of a variety of foods with complex combinations of nutrients. A more rational approach to nephrolithiasis prevention would be to base dietary advice on the cumulative effects of foods and different dietary patterns rather than single nutrients. Study Design: Randomized controlled trial. Setting & Participants: Recurrent stone formers with hyperoxaluria (urine oxalate > 40 mg/d). Intervention: The intervention group was asked to follow a calorie-controlled Dietary Approaches to Stop Hypertension (DASH)-style diet (a diet high in fruit, vegetables, whole grains, and low-fat dairy products and low in saturated fat, total fat, cholesterol, refined grains, sweets, and meat), whereas the control group was prescribed a low-oxalate diet. Study length was 8 weeks. Outcomes: Primary: change in urinary calcium oxalate supersaturation. Secondary: Changes in 24-hour urinary composition. Results: 57 participants were randomly assigned (DASH group, 29; low-oxalate group, 28). 41 participants completed the trial (DASH group, 21; low-oxalate group, 20). As-treated analysis showed a trend for urinary oxalate excretion to increase in the DASH versus the low-oxalate group (point estimate of difference, 9.0 mg/d; 95% CI, -1.1 to 19.1 mg/d; P - 0.08). However, there was a trend for calcium oxalate supersaturation to decrease in the DASH versus the low-oxalate group (point estimate of difference, -1.24; 95% CI, -2.80 to 0.32; P 5 0.08) in association with an increase in magnesium and citrate excretion and urine pH in the DASH versus low-oxalate group. Limitations: Limited sample size, as-treated analysis, nonsignificant results. Conclusions: The DASH diet might be an effective alternative to the low-oxalate diet in reducing calcium oxalate supersaturation and should be studied more. (C) Published by Elsevier Inc. on behalf of the National Kidney Foundation, Inc.