title: The effects of tea on psychophysiological stress responsivity and post-stress recovery: a randomised double-blind trial.
abstract: BACKGROUND
  Tea has anecdotally been associated with stress relief, but this has seldom been tested scientifically.
  
  
  OBJECTIVE
  To investigate the effects of 6 weeks of black tea consumption, compared with matched placebo, on subjective, cardiovascular, cortisol and platelet responses to acute stress, in a parallel group double-blind randomised design.
  
  
  METHODS
  Seventy-five healthy nonsmoking men were withdrawn from tea, coffee and caffeinated beverages for a 4-week wash-out phase during which they drank four cups per day of a caffeinated placebo. A pretreatment laboratory test session was carried out, followed by either placebo (n = 38) or active tea treatment (n = 37) for 6 weeks, then, a final test session. Cardiovascular measures were obtained before, during and after two challenging behavioural tasks, while cortisol, platelet and subjective measures were assessed before and after tasks.
  
  
  RESULTS
  The tasks induced substantial increases in blood pressure, heart rate and subjective stress ratings, but responses did not differ between tea and placebo treatments. Platelet activation (assessed using flow cytometry) was lower following tea than placebo treatment in both baseline and post-stress samples (P < 0.005). The active tea group also showed lower post-task cortisol levels compared with placebo (P = 0.032), and a relative increase in subjective relaxation during the post-task recovery period (P = 0.036).
  
  
  CONCLUSIONS
  Compared with placebo, 6 weeks of tea consumption leads to lower post-stress cortisol and greater subjective relaxation, together with reduced platelet activation. Black tea may have health benefits in part by aiding stress recovery.
authors.affiliation: Department of Epidemiology and Public Health, University College London, 1-19 Torrington Place, London, UK. a.steptoe@ucl.ac.uk
authors.forename: Andrew
authors.initials: A
authors.lastname: Steptoe
authors.forename: E Leigh
authors.initials: EL
authors.lastname: Gibson
authors.forename: Raisa
authors.initials: R
authors.lastname: Vuononvirta
authors.forename: Emily D
authors.initials: ED
authors.lastname: Williams
authors.forename: Mark
authors.initials: M
authors.lastname: Hamer
authors.forename: Jane A
authors.initials: JA
authors.lastname: Rycroft
authors.forename: Jorge D
authors.initials: JD
authors.lastname: Erusalimsky
authors.forename: Jane
authors.initials: J
authors.lastname: Wardle
mesh_terms: D000223:Adaptation, Psychological / Q000187:drug effects* / Q000502:physiology; D000293:Adolescent; D000328:Adult; D000339:Affect / Q000187:drug effects; D001143:Arousal / Q000187:drug effects* / Q000502:physiology; D001794:Blood Pressure / Q000187:drug effects*; D002110:Caffeine / Q000494:pharmacology; D004311:Double-Blind Method; D005260:Female; D006339:Heart Rate / Q000187:drug effects*; D006801:Humans; D006854:Hydrocortisone / Q000097:blood*; D008297:Male; D008875:Middle Aged; D015539:Platelet Activation / Q000187:drug effects*; D012931:Social Environment; D013060:Speech / Q000187:drug effects; D013315:Stress, Psychological / Q000150:complications*; D013662:Tea
chemical_list: D013662:Tea; D002110:Caffeine; D006854:Hydrocortisone