The effects of tea on psychophysiological stress responsivity and post-stress recovery: a randomised double-blind trial

Daily cups of tea will help you recover far more quickly from the stresses of everyday life, that is according to a new study by UCL (University College London) scientists. New evidence has shown that black tea has an effect on stress hormone levels in the body.

This study, published in the journal “Psychopharmacology”, found out that people who drink tea are able to de-stress more quickly than those who drink a fake tea substitute. In addition, the study participants drinking a black tea concoction four times a day for six weeks had lower levels of the stress hormone cortisol in their blood after a stressful event, in comparison to a control group who drank the fake or placebo teas for the same period of time.

In the study, 75 young male regular tea drinkers were split into two seperate groups and monitored for six weeks. All gave up their normal tea, coffee and other caffeinated beverages, one group was given a fruit flavored caffeinated tea mixture comprised of the constituents of an average cup of black tea. The other control group was given a caffeinated placebo identical in taste, but without any of the active tea ingredients. All drinks were tea colored, but designed to mask some of the normal sensory clues one can associate with tea (such as smell, taste and familiarity of the brew), to eliminate confounding factors such as the ‘comforting’ effect of drinking a cup of tea.

Both of these groups were subject to challenging tasks, while their cortisol (stress hormone), blood pressure, blood platelet and self-rated levels of stress were measured. In one of the tasks, volunteers were exposed to 1 of 3 stressful situations (threat of joblessness, criminal accusation or an incident in a nursing home), where they had to prepare a verbal response and argue their case in front of a camera.

These tasks triggered substantial increases in heart rate, blood pressure and subjective stress ratings for both of the groups. This insured similar stress levels were induced in both groups. However, fifty minutes after the task, cortisol levels had dropped by a stunning average of 47 per cent in the tea drinking group compared with 27 per cent in the fake tea group.

UCL researchers also found that blood platelet activation linked to blood clotting and the risk of heart attacks was lower in the real tea drinking group, and that this group reported a greater degree of relaxation in the recovery period after the task.

Professor Andrew Steptoe, UCL Department of Epidemiology and Public Health, says: “Drinking tea has traditionally been associated with stress relief, and many people believe that drinking tea helps them relax after facing the stresses of everyday life. However, scientific evidence for the relaxing properties of tea is quite limited. This is one of the first studies to assess tea in a double-blind placebo controlled design - that is, neither we nor the participants knew whether they were drinking real or fake tea. This means that any differences were due to the biological ingredients of tea, and not to the relaxing situations in which people might drink tea, whether they were familiar with the taste and liked it, and so on.

“We do not know what ingredients of tea were responsible for these effects on stress recovery and relaxation. Tea is chemically very complex, with many different ingredients. Ingredients such as catechins, polyphenols, flavonoids and amino acids have been found to have effects on neurotransmitters in the brain, but we cannot tell from this research which ones produced the differences.

“Nevertheless, our study suggests that drinking black tea may speed up our recovery from the daily stresses in life. Although it does not appear to reduce the actual levels of stress we experience, tea does seem to have a greater effect in bringing stress hormone levels back to normal. This has important health implications, because slow recovery following acute stress has been associated with a greater risk of chronic illnesses such as coronary heart disease.”

Abstract
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.

Andrew Steptoe1 Contact Information, E. Leigh Gibson1, Raisa Vounonvirta1, Emily D. Williams1, Mark Hamer1, Jane A. Rycroft2, Jorge D. Erusalimsky3 and Jane Wardle1
(1) Department of Epidemiology and Public Health, University College London, 1-19 Torrington Place, London, WC1E 6BT, UK
(2) Unilever Research Colworth, Bedford, UK
(3) Wolfson Institute for Biomedical Research, University College London, London, WC1E 6BT, UK

Received: 12 June 2006 Accepted: 9 August 2006 Published online: 30 September 2006