title: Probiotic Supplements Beneficially Affect Tryptophan-Kynurenine Metabolism and Reduce the Incidence of Upper Respiratory Tract Infections in Trained Athletes: A Randomized, Double-Blinded, Placebo-Controlled Trial.
abstract: BACKGROUND
  Prolonged intense exercise has been associated with transient suppression of immune function and an increased risk of infections. In this context, the catabolism of amino acid tryptophan via kynurenine may play an important role. The present study examined the effect of a probiotic supplement on the incidence of upper respiratory tract infections (URTI) and the metabolism of aromatic amino acids after exhaustive aerobic exercise in trained athletes during three months of winter training.
  
  
  METHODS
  Thirty-three highly trained individuals were randomly assigned to probiotic (PRO,n= 17) or placebo (PLA,n= 16) groups using double blind procedures, receiving either 1 × 1010colony forming units (CFU) of a multi-species probiotic (Bifidobacterium bifidumW23,Bifidobacterium lactisW51,Enterococcus faeciumW54,Lactobacillus acidophilusW22,Lactobacillus brevisW63, andLactococcus lactisW58) or placebo once per day for 12 weeks. The serum concentrations of tryptophan, phenylalanine and their primary catabolites kynurenine and tyrosine, as well as the concentration of the immune activation marker neopterin were determined at baseline and after 12 weeks, both at rest and immediately after exercise. Participants completed a daily diary to identify any infectious symptoms.
  
  
  RESULTS
  After 12 weeks of treatment, post-exercise tryptophan levels were lowered by 11% (a significant change) in the PLA group compared to the concentrations measured before the intervention (p= 0.02), but remained unchanged in the PRO group. The ratio of subjects taking the placebo who experienced one or more URTI symptoms was increased 2.2-fold compared to those on probiotics (PLA 0.79, PRO 0.35;p= 0.02).
  
  
  CONCLUSIONS
  Data indicate reduced exercise-induced tryptophan degradation rates in the PRO group. Daily supplementation with probiotics limited exercise-induced drops in tryptophan levels and reduced the incidence of URTI, however, did not benefit athletic performance.
authors.affiliation: Division of Medical Biochemistry, Biocenter, Medical University of Innsbruck, Innrain 80, 6020 Innsbruck, Austria. Barbara.Strasser@i-med.ac.at.
authors.forename: Barbara
authors.initials: B
authors.lastname: Strasser
authors.affiliation: Division of Biological Chemistry, Biocenter, Medical University of Innsbruck, Innrain 80, 6020 Innsbruck, Austria. M.Sc.DanielaGeiger@gmail.com.
authors.forename: Daniela
authors.initials: D
authors.lastname: Geiger
authors.affiliation: Division of Biological Chemistry, Biocenter, Medical University of Innsbruck, Innrain 80, 6020 Innsbruck, Austria. M.Schauer@hotmail.com.
authors.forename: Markus
authors.initials: M
authors.lastname: Schauer
authors.affiliation: Division of Medical Biochemistry, Biocenter, Medical University of Innsbruck, Innrain 80, 6020 Innsbruck, Austria. Johanna.Gostner@i-med.ac.at.
authors.forename: Johanna M
authors.initials: JM
authors.lastname: Gostner
authors.affiliation: Department of Sport Science, Medical Section, University of Innsbruck, Fuerstenweg 189, 6020 Innsbruck, Austria. Hannes.Gatterer@uibk.ac.at.
authors.forename: Hannes
authors.initials: H
authors.lastname: Gatterer
authors.affiliation: Department of Sport Science, Medical Section, University of Innsbruck, Fuerstenweg 189, 6020 Innsbruck, Austria. Martin.Burtscher@uibk.ac.at.
authors.forename: Martin
authors.initials: M
authors.lastname: Burtscher
authors.affiliation: Division of Biological Chemistry, Biocenter, Medical University of Innsbruck, Innrain 80, 6020 Innsbruck, Austria. Dietmar.Fuchs@i-med.ac.at.
authors.forename: Dietmar
authors.initials: D
authors.lastname: Fuchs
mesh_terms: D000328:Adult; D056352:Athletes; D001317:Austria; D015415:Biomarkers / Q000097:blood; D004311:Double-Blind Method; D005260:Female; D000069196:Gastrointestinal Microbiome / Q000276:immunology; D006304:Health Status; D006801:Humans; D007737:Kynurenine / Q000097:blood*; D008297:Male; D019798:Neopterin; D010649:Phenylalanine / Q000097:blood; D064797:Physical Conditioning, Human; D010807:Physical Endurance; D010809:Physical Fitness; D019936:Probiotics / Q000008:administration & dosage*; D012141:Respiratory Tract Infections / Q000097:blood / Q000276:immunology / Q000382:microbiology / Q000517:prevention & control*; D012307:Risk Factors; D012621:Seasons; D013997:Time Factors; D014364:Tryptophan / Q000097:blood*; D014443:Tyrosine / Q000097:blood; D055815:Young Adult
chemical_list: D015415:Biomarkers; D007737:Kynurenine; D014443:Tyrosine; D010649:Phenylalanine; D019798:Neopterin; D014364:Tryptophan
keywords: intense exercise; kynurenine; probiotics; tryptophan; upper respiratory tract infections