Abstract
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, 9.0mg/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. 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.
Highlights
Patients with nephrolithiasis and hyperoxaluria generally are advised to follow a lowoxalate diet
Ninety-one individuals were screened for inclusion in the study, 57 of whom had baseline mean urinary oxalate excretion .40 mg/d
Four patients randomly assigned to Dietary Approaches to Stop Hypertension (DASH) and 2 patients randomly assigned to low-oxalate diets did not follow their assigned diet because their jobs did not allow them to plan for their diets, and so were excluded
Summary
Patients with nephrolithiasis and hyperoxaluria generally are advised to follow a lowoxalate diet. The restriction of dietary oxalate may reduce urine oxalate, and O formigenes colonization because the organism could be deprived of its food source.[13,14] The net effect of these opposing influences is unknown Given these complicating factors, a more rational approach to solve the problem of nephrolithiasis might be based on the study of the cumulative effects of foods and different dietary patterns on urinary saturation, rather than on the study of the effect of single nutrients. In a previous observational study, people following diets that resembled DASH were found to be less likely to form stones.[15] The basis for this effect was attributable in part to increased urine citrate excretion.[16] A DASH-style diet has higher oxalate and vitamin C content as a result of higher intakes of fruits, vegetables, and nuts, and it would be expected to increase urinary oxalate. We hypothesized that a DASH-like dietary pattern would be superior to a low-oxalate diet in lowering urinary calcium oxalate supersaturation
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