title: Does long-term creatine supplementation impair kidney function in resistance-trained individuals consuming a high-protein diet?
abstract: BACKGROUND
  The aim of this study was to determine the effects of creatine supplementation on kidney function in resistance-trained individuals ingesting a high-protein diet.
  
  
  METHODS
  A randomized, double-blind, placebo-controlled trial was performed. The participants were randomly allocated to receive either creatine (20 g/d for 5 d followed by 5 g/d throughout the trial) or placebo for 12 weeks. All of the participants were engaged in resistance training and consumed a high-protein diet (i.e., ≥ 1.2 g/Kg/d). Subjects were assessed at baseline (Pre) and after 12 weeks (Post). Glomerular filtration rate was measured by 51Cr-EDTA clearance. Additionally, blood samples and a 24-h urine collection were obtained for other kidney function assessments.
  
  
  RESULTS
  No significant differences were observed for 51Cr-EDTA clearance throughout the trial (Creatine: Pre 101.42 ± 13.11, Post 108.78 ± 14.41 mL/min/1.73m2; Placebo: Pre 103.29 ± 17.64, Post 106.68 ± 16.05 mL/min/1.73m2; group x time interaction: F = 0.21, p = 0.64). Creatinine clearance, serum and urinary urea, electrolytes, proteinuria, and albuminuria remained virtually unchanged.
  
  
  CONCLUSIONS
  A 12-week creatine supplementation protocol did not affect kidney function in resistance-trained healthy individuals consuming a high-protein diet; thus reinforcing the safety of this dietary supplement.
  
  
  BACKGROUND
  ClinicalTrials.gov NCT01817673.
authors.affiliation: School of Physical Education and Sport - Laboratory of Applied Nutrition and Metabolism, University of Sao Paulo, Av Mello de Moraes, 65, Sao Paulo, SP 05508-030, Brazil. gualano@usp.br.
authors.forename: Rebeca
authors.initials: R
authors.lastname: Lugaresi
authors.forename: Marco
authors.initials: M
authors.lastname: Leme
authors.forename: Vítor
authors.initials: V
authors.lastname: de Salles Painelli
authors.forename: Igor Hisashi
authors.initials: IH
authors.lastname: Murai
authors.forename: Hamilton
authors.initials: H
authors.lastname: Roschel
authors.forename: Marcelo Tatit
authors.initials: MT
authors.lastname: Sapienza
authors.forename: Antonio Herbert
authors.initials: AH
authors.lastname: Lancha Junior
authors.forename: Bruno
authors.initials: B
authors.lastname: Gualano