Dietary animal protein and urinary supersaturation in renal stone disease

Eight stone-forming patients were given diets that were high (HPD) and low (LPD) in dietary animal protein, each for two weeks. Urines were collected by the end of each diet period. Urinary calcium, phosphate, urate and acids were increased on HPD whereas citrate and urine-pH decreased. The urinary supersaturation and thereby the risk of forming crystals and stones of uric acid and ammonium urate was increased on HPD. The supersaturation of calcium oxalate was unchanged, but the inhibition of calcium oxalate crystallisation may have become unfavourably affected.