title: Effect of L-Methionine on the Risk of Phosphate Stone Formation.
abstract: OBJECTIVE
  To determine the physiological effects following administration of the sulfur-containing amino acid L-methionine on urinary risk factors for calcium oxalate and phosphate stone formation under controlled, standardized conditions.
  
  
  METHODS
  Twelve healthy subjects were studied while consuming a standardized diet for 6 days. Day 5 was considered as control day. On day 6 (test day), participants received 1500 mg L-methionine at 9 AM. On the control and test days, 24-hour fractional urine collections were obtained.
  
  
  RESULTS
  After single-dose administration of L-methionine, 24-hour fractional urinary pH decreased to values between 5.98 and 6.32. Urinary sulfate excretion, a direct marker for the metabolism of L-methionine, and ammonium excretion, which reflects the increase in net acid production, increased significantly after L-methionine administration. Urinary calcium excretion did not differ between control and test day (5.55 vs 5.45 mmol/24 hours; P = .754). The relative supersaturation of brushite and struvite decreased significantly by 25% (P = .010) and 34% (P = .049), respectively, whereas the risk of calcium oxalate stone formation was not affected by application of L-methionine (P = .477).
  
  
  CONCLUSIONS
  The present findings show that L-methionine effectively decreases urinary pH and the risk of struvite and calcium phosphate stone formation in healthy subjects. Hypercalciuria is not expected to occur at physiological doses of L-methionine.
authors: University Stone Centre, Department of Urology, University of Bonn, Bonn, Germany. Electronic address: Roswitha.Siener@ukb.uni-bonn.de.
authors: Roswitha
authors: R
authors: Siener
authors: University Stone Centre, Department of Urology, University of Bonn, Bonn, Germany.
authors: Florian
authors: F
authors: Struwe
authors: University Stone Centre, Department of Urology, University of Bonn, Bonn, Germany.
authors: Albrecht
authors: A
authors: Hesse
mesh_terms: D000328:Adult; D002118:Calcium / Q000652:urine; D002130:Calcium Phosphates / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D064368:Healthy Volunteers; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007669:Kidney Calculi / Q000175:diagnosis / Q000378:metabolism / Q000517:prevention & control*; D008297:Male; D008715:Methionine / Q000008:administration & dosage* / Q000493:pharmacokinetics; D012307:Risk Factors; D013431:Sulfates / Q000652:urine; D016896:Treatment Outcome; D016482:Urinalysis; D055815:Young Adult
chemical_list: D002130:Calcium Phosphates; D013431:Sulfates; C020243:calcium phosphate; D008715:Methionine; D002118:Calcium