 The easy way to relax |
The study of black tea - instead of green or herbal varieties - found it helps cut levels of the stress hormone cortisol circulating in the blood.
They found people who drank tea were able to de-stress more quickly than those who drank a tea substitute.
The University College London study is in the journal Psychopharmacology.
In the study, 75 young male regular tea drinkers were split into two groups and monitored for six weeks.
They all gave up their normal tea, coffee and caffeinated beverages, and then one group was given a fruit-flavoured caffeinated tea mixture made up of the constituents of an average cup of black tea.
The other group was given a caffeinated placebo identical in taste, but devoid of the active tea ingredients.
Stressful tasks
All drinks were tea-coloured, but were designed to mask some of the normal sensory cues associated with tea drinking (such as smell, taste and familiarity of the brew).
This was designed to eliminate confounding factors such as the 'comforting' effect of drinking a cup of tea.
Both groups were subjected to challenging tasks, while their cortisol, blood pressure, blood platelet and self-rated levels of stress were measured.
In one task, volunteers were exposed to one of three stressful situations (threat of unemployment, a shop-lifting 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.
The tasks triggered substantial increases in blood pressure, heart rate and subjective stress ratings in both of the groups.
However, 50 minutes after the task, cortisol levels had dropped by an average of 47% in the tea-drinking group compared with 27% in the fake tea group.
Blood platelet activation - linked to blood clotting and the risk of heart attacks - was also lower in the tea drinkers.
In addition, this group reported a greater degree of relaxation in the recovery period after the task.
Complex drink
Researcher Professor Andrew Steptoe said: "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."
Professor Steptoe said it was unclear what ingredients in tea were responsible.
He said it was very complex, and ingredients such as catechins, polyphenols, flavonoids and amino acids had all been found to affect neurotransmitters in the brain.
Nevertheless, the 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."
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