Dietary influence on serum and urinary oxalate in healthy subjects and oxalate stone formers

With a new enzymatic method, the dietary influence of oxalate, glycine, protein, and ascorbic acid on serum and urinary oxalate has been examined. Healthy and oxalate stone-forming subjects were compared. Two doses of sodium oxalate (130 and 400 mg daily) were administered. The high dose induced significant hyperoxaluria. No changes of serum oxalate were seen. Neither glycine (4.5 g daily) nor protein (50 g daily, 50% animal protein) had any effect on serum or urinary oxalate. Urinary oxalate excretion did not increase upon ingestion of large amounts of ascorbic acid (1--6 g daily), but serum oxalate levels were significantly elevated. The value of severe dietary restrictions concerning the compounds examined here seems to be questionable, as a significant increase of urinary oxalate excretion is lacking.