title: Effects of oral administration of caffeine and D-ribose on mental fatigue.
abstract: OBJECTIVE
  We examined the effects of administering two different candidate antifatigue substances, caffeine and D-ribose, on mental fatigue.
  
  
  METHODS
  In a double-blinded, placebo-controlled, three-way crossover design, 17 healthy volunteers were randomized to oral caffeine (200 mg/d), D-ribose (2000 mg/d), or placebo for 8 d. As fatigue-inducing mental tasks, subjects performed a 30-min Uchida-Kraepelin psychodiagnostic test and a 30-min advanced trail-making test on four occasions.
  
  
  RESULTS
  During the tasks, the task performance of the caffeine group was better than that of the placebo group. However, after the fatigue-inducing tasks, although subjective perception of fatigue, motivation, or sleepiness was not significantly different, plasma branched-chain amino acid levels in the caffeine group were lower than those of the placebo group. Administration of D-ribose had no effect.
  
  
  CONCLUSIONS
  Because plasma branched-chain amino acid levels are decreased by mental fatigue, these results suggest that administration of caffeine improved task performance through the enhancement of central nervous system activity without increasing the sensation of fatigue. However, further decreases in branched-chain amino acid levels indicate that caffeine might promote deeper fatigue than placebo. Unfortunately, research subsequent to our study design has shown that D-ribose dosing higher than we used is needed to see a clinical effect and therefore no conclusions can be made from this study as to the efficacy of D-ribose.
authors.affiliation: Department of Physiology, Osaka City University Graduate School of Medicine, Osaka, Japan. suzuka126@med.osaka-cu.ac.jp
authors.forename: Suzuka
authors.initials: S
authors.lastname: Ataka
authors.forename: Masaaki
authors.initials: M
authors.lastname: Tanaka
authors.forename: Satoshi
authors.initials: S
authors.lastname: Nozaki
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Mizuma
authors.forename: Kei
authors.initials: K
authors.lastname: Mizuno
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Tahara
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Sugino
authors.forename: Tomoko
authors.initials: T
authors.lastname: Shirai
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Kajimoto
authors.forename: Hirohiko
authors.initials: H
authors.lastname: Kuratsune
authors.forename: Osami
authors.initials: O
authors.lastname: Kajimoto
authors.forename: Yasuyoshi
authors.initials: Y
authors.lastname: Watanabe
mesh_terms: D000284:Administration, Oral; D000324:Adrenocorticotropic Hormone / Q000097:blood; D000328:Adult; D000597:Amino Acids, Branched-Chain / Q000097:blood*; D002110:Caffeine / Q000008:administration & dosage / Q000627:therapeutic use*; D000697:Central Nervous System Stimulants / Q000008:administration & dosage / Q000627:therapeutic use*; D018592:Cross-Over Studies; D004311:Double-Blind Method; D005221:Fatigue / Q000097:blood / Q000188:drug therapy*; D005260:Female; D006801:Humans; D006854:Hydrocortisone / Q000097:blood; D008297:Male; D008606:Mental Processes / Q000187:drug effects; D011930:Reaction Time / Q000187:drug effects; D012266:Ribose / Q000008:administration & dosage / Q000627:therapeutic use*; D013647:Task Performance and Analysis; D016896:Treatment Outcome
chemical_list: D000597:Amino Acids, Branched-Chain; D000697:Central Nervous System Stimulants; D002110:Caffeine; D012266:Ribose; D000324:Adrenocorticotropic Hormone; D006854:Hydrocortisone