SUBSTITUTING MILK FOR APPLE JUICE DOES NOT INCREASE KIDNEY-STONE RISKIN MOST NORMOCALCIURIC ADULTS WHO FORM CALCIUM-OXALATE STONES

Objective Increasing intake of dietary calcium from less than 400 mg t o 800 mg daily may decrease the absorption of dietary oxalate, which i n turn would decrease urinary oxalate excretion. The effect of substit uting milk for apple juice on urine composition and risk of calcium ox alate precipitability was studied. Subjects Twenty-one normocalciuric adults with a history of at least 1 calcium oxalate stone and urinary oxalate excretion exceeding 275 mu mol/day on their self-selected diet . Design Randomized crossover trial. Intervention Each participant con sumed two moderate-oxalate (2,011 mu mol/day) study diets, which were identical except that one contained 360 mt milk and the other containe d 540 mt apple juice as the beverage with meals. Setting Four days fre e-living then 2 days in the metabolic unit of a university nutrition d epartment. Main outcome measure Tiselius risk index for calcium oxalat e precipitability calculated from urine composition. Statistical analy ses Paired t tests. Results Twenty-four hour urinary oxalate excretion was 18% lower (P<.0001) on the milk diet vs the juice diet: 423 vs 51 4 mu mol, respectively. Calcium excretion was 17% higher (P<.05) on th e milk vs juice diet: 4.7 vs 3.9 mmol, respectively. Urinary magnesium and citrate excretion, volume, and Tiselius risk index did not differ between diets. Applications Substituting 360 mt milk daily for apple juice with meals in a diet containing moderate amounts of dietary oxal ate from whole grains, legumes, fruits, and vegetables does not increa se the risk index of calcium oxalate precipitability in most normocalc iuric adults who form stones.