The study found that people who drank tea were able to de-stress more quickly than those who drank a fake tea substitute. Furthermore, the study participants – who drank a black tea concoction four times a day for six weeks – were found to have lower levels of the stress hormone cortisol in their blood after a stressful event, compared with a control group who drank the fake or placebo tea for the same period of time.
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, 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 – the control group – was given a caffeinated placebo identical in taste, but devoid of the active tea ingredients. 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), 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. The tasks triggered substantial increases in blood pressure, heart rate and subjective stress ratings in both of the groups. In other words, similar stress levels were induced in both groups. However, 50 minutes after the task, cortisol levels had dropped by an 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 tea drinkers, and that this group reported a greater degree of relaxation in the recovery period after the task.
MEDICA.de; Source: University College London