Diets with either beef or plant proteins reduce risk of calcium oxalate precipitation in patients with a history of calcium kidney stones.

OBJECTIVE: To determine the effect of substituting equal amounts of dietary protein as animal protein (beef) for plant protein (legumes, seeds, nuts, and grains) on urinary components associated with calcium oxalate precipitability risk. DESIGN: Randomized crossover trial. SUBJECTS: Twenty-three normocalciuric patients with a history of calcium kidney stones (8 women and 15 men, mean age 50.7+/-14.6 years) with 24-hour urinary calcium < or =10.3 micromol, 24 hour urinary oxalate excretion between 228 and 963 micromol, and a urinary calcium increase of < or =1.0 micromol in 4 hours after a 25 micromol oral calcium load. SETTING: Four-day, free-living adaptation period, followed by 2-day metabolic unit study. INTERVENTION: The study compared consumption of 2 servings of beef (43 g protein for women and 50 g for men) daily with an equal amount of protein from plant foods including legumes, nuts, and grains. MAIN OUTCOME MEASURES: Tiselius risk index (TRI) for calcium oxalate precipitability calculated from urinary calcium, oxalate, magnesium, citrate, and volume. STATISTICAL ANALYSES: Paired t tests. RESULTS: Urinary calcium, oxalate, magnesium, citrate, phosphorus, volume, and TRI did not differ between diets. Urinary sodium and potassium were higher for patients on the plant protein diet. After correcting for variations in urinary sodium and potassium between diets, the difference in urinary calcium remained insignificant. TRI was lower on both beef- and plant-protein diets compared with self-selected prestudy diets for all participants. CONCLUSION/APPLICATIONS: Balanced diets containing moderate amounts of either beef or plant protein are equally effective in reducing calcium oxalate kidney stone risk based on changes in urinary composition.