Black tea eases stress by lowering blood levels of the stress hormone cortisol, says a British study in the journal Psychopharmacology.
The six-week study of 75 people found that those who drank black tea were able to de-stress more quickly than those who drank a caffeinated tea substitute, BBC News reported.
The participants were assigned challenging tasks while their cortisol, blood pressure, blood platelet, and self-rated levels of stress were measured by the researchers. During these tasks, both groups of study participants experienced large increases in blood pressure, heart rate, and self-rated levels of stress.
However, 50 minutes after the stressful tasks, cortisol levels dropped by an average of 47 percent among those who drank black tea and 27 percent among those who drank the tea substitute.
The study also found that the tea drinkers had lower blood platelet activation, which is associated with blood clotting and heart-attack risk, BBC News reported.
It's unclear which ingredients in black tea help reduce stress, the University College London researchers said.
HealthDay News, October 6, 2006
