Comparison of DASH With Oxalate Restricted Diet on Urine in Recurrent Stone Formers With Hyperoxaluria

Oxalate restricted diet is routinely prescribed in clinical practice of nephrolithiasis patients with hyperoxaluria. The effect of dietary oxalate on urinary oxalate is however controversial. Some studies do not implicate dietary oxalate as a major risk factor for nephrolithiasis. The Dietary Approaches to Stop Hypertension (DASH) diet, which is high in fruits and vegetables, moderate in low-fat dairy products, and low in animal protein represents a novel potential means of kidney stone prevention. The effect of a DASH-style diet on relative urinary supersaturations is however uncertain. Higher consumption of fruits and vegetables may increase urinary oxalate but also increases urinary citrate, an important inhibitor of calcium saturation.All the above data lead us to hypothesize that a DASH diet other than an oxalate restricted diet, which is routinely administered in clinical practice, might be beneficial in lowering urinary relative supersaturations of calcium oxalate in recurrent stone formers with hyperoxaluria. Recurrent stone formers with hyperoxaluria (urine oxalate\>32.8) are allocated into 2 groups. The first group is prescribed an oxalate restricted diet. The second group are asked to follow a calorie-controlled DASH diet plan while drink water in the same amounts. 24-h urine is collected 2 times before study visits at baseline, 1 time on week 6 and 2 times at the end of the study.