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, 9.0mg/d; 95% CI, -1.1 to 19.1mg/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.
Trial registration: ClinicalTrials.gov NCT01650935.
Keywords: Dietary Approaches to Stop Hypertension (DASH) diet; calcium oxalate supersaturation; clinical trial; hyperoxaluria; kidney stone; nephrolithiasis; oxalate.
Copyright © 2014. Published by Elsevier Inc.