Study Connects Black Tea to Reduced Stress

Regular tea consumption might help people recover more quickly from stress, according to a new study by University College London (UCL) researchers. New scientific evidence shows that black tea has an effect on stress hormone levels in the body. The results of this research were published in Psychopharmacology online on Sept. 30 (see http://www.springerlink.com/content/m226111566k24u65/).

The researchers--Andrew Steptoe, Leigh Gibson, Raisa Vounonvirta, Emily Williams, Mark Hamer, Jorge Erusalimsky and Jane Wardle from UCL, as well as Jane Rycroft of Unilever R&D Colworth, Bedford, England--split 75 young male regular tea drinkers into two groups and monitored them for six weeks. The study participants all gave up their normal tea, coffee and caffeinated beverages. One group was given a fruit-flavored caffeinated tea mixture made up of the constituents of an average cup of black tea. The control group was given a caffeinated placebo identical in taste, but devoid of the active tea ingredients. Both drinks looked like regular tea, but were designed to mask some of the normal sensory cues associated with tea drinking--such as smell and flavor--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. 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 control group. The 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.

The researchers noted that they do not know what ingredients of tea were responsible for these effects on stress recovery and relaxation. Catechins, polyphenols, flavonoids and amino acids in tea have all demonstrated effects on neurotransmitters in the brain.

This study was partly funded by Unilever and the Biotechnology and Biological Sciences Research Council, Swindon, England (see http://www.bbsrc.ac.uk/).