Effects of oral administration of caffeine and D-ribose on mental fatigue.
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.
Ataka
Suzuka
S
Department of Physiology, Osaka City University Graduate School of Medicine, Osaka, Japan. suzuka126@med.osaka-cu.ac.jp
Tanaka
Masaaki
M
Nozaki
Satoshi
S
Mizuma
Hiroshi
H
Mizuno
Kei
K
Tahara
Tsuyoshi
T
Sugino
Tomohiro
T
Shirai
Tomoko
T
Kajimoto
Yoshitaka
Y
Kuratsune
Hirohiko
H
Kajimoto
Osami
O
Watanabe
Yasuyoshi
Y
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
D000597:Amino Acids, Branched-Chain; D000697:Central Nervous System Stimulants; D002110:Caffeine; D012266:Ribose; D000324:Adrenocorticotropic Hormone; D006854:Hydrocortisone