The effects of tea on psychophysiological stress responsivity and post-stress recovery by Steptoe A, Gibson EL, Vuononvirta R, Williams ED, Hamer M, Rycroft JA, Erusalimsky JD, Wardle J.
RATIONALE: Tea has anecdotally been associated with stress
relief, but this has seldom been tested scientifically.
OBJECTIVES: 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.
MATERIALS AND 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were withdrawn from tea, coffee and caffeinated beverages for a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.
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