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 = 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. 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. Randomized controlled trial. Recurrent stone formers with hyperoxaluria (urine oxalate > 40 mg/d). 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. Primary: change in urinary calcium oxalate supersaturation. Changes in 24-hour urinary composition. 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 = 0.08) in association with an increase in magnesium and citrate excretion and urine pH in the DASH versus low-oxalate group. Limited sample size, as-treated analysis, nonsignificant results. The DASH diet might be an effective alternative to the low-oxalate diet in reducing calcium oxalate supersaturation and should be studied more.