title: Nitrate Supplementation, Exercise, and Kidney Function: Are There Detrimental Effects?
abstract: OBJECTIVE
  Recently, dietary supplementation with inorganic nitrate (NO3) has been proposed to endurance athletes to increase their performance. However, it has been suggested that an excess of NO3 might be harmful. The present study analyzed the effect of NO3 supplementation on kidney function.
  
  
  METHODS
  Thirteen young male subjects performed a 20-min cycling exercise at 85% of the maximal oxygen capacity. Seven days before exercise, the subjects ingested either a placebo (Pl) or 450 mg of potassium nitrate (PN) per day. Venous blood samples and urine collections were collected before and immediately after exercise and after 60 min of recovery. Glomerular filtration rates (GFR) and clearances (Cl) were calculated from serum content and urine output for creatinine (Crn), albumin (Alb), and urea.
  
  
  RESULTS
  Under resting conditions, GFR and all clearance measures did not differ between Pl and PN. Immediately after exercise, GFR remained stable in both Pl and PN, whereas Cl-urea decreased significantly (P < 0.05) in Pl (-44%) and PN (-49%). Alb urine outputs were enhanced by 18- to 20-fold in Pl and PN, respectively (P < 0.05). After the recovery period, GFR remained enhanced under Pl conditions, whereas Cl-urea returned to initial values in placebo and nitrate supplementation. Alb output and Cl-Alb remained enhanced under PN conditions.
  
  
  CONCLUSIONS
  These results mainly indicate that dietary nitrate supplementation over a week does not induce any specific kidney function modifications either at rest or during sustained submaximal exercise as compared with Pl.
authors.affiliation: Laboratory for Biometry and Exercise Nutrition, Faculty of Motor Sciences, Free University of Brussels (ULB Belgium), Brussels, BELGIUM.
authors.forename: Alain
authors.initials: A
authors.lastname: Carpentier
authors.forename: Séverine
authors.initials: S
authors.lastname: Stragier
authors.forename: Camille
authors.initials: C
authors.lastname: Bréjeon
authors.forename: Jacques R
authors.initials: JR
authors.lastname: Poortmans
mesh_terms: D000418:Albumins / Q000032:analysis; D003404:Creatinine / Q000652:urine; D019587:Dietary Supplements; D004311:Double-Blind Method; D015444:Exercise; D005919:Glomerular Filtration Rate / Q000187:drug effects*; D006801:Humans; D008297:Male; D009566:Nitrates / Q000008:administration & dosage*; D017680:Potassium Compounds / Q000008:administration & dosage*; D014508:Urea / Q000097:blood / Q000652:urine; D055815:Young Adult
chemical_list: D000418:Albumins; D009566:Nitrates; D017680:Potassium Compounds; D014508:Urea; D003404:Creatinine; C023844:potassium nitrate