Department of Food Science, University of Arkansas, has studied the effect of tea (instant tea powder, pure and sweetened with sugar, sucralose and stevia) on the emotional state of consumers exposed to acute stressor. The results proved that only sugar-sweetened tea had sedative effect — neither pure tea, nor tea with non-nutritive sweeteners calm down people after stress.
For the experiment, a group of 50 healthy adults (25 women and 25 men) were selected, who, on two days, one week apart, were questioned for their emotional state, then they were given four teas (unsweetened, sweetened with sugar, sweetened with stevia and sucralose), after then were questioned after drinking each tea. One of the days of questioning was for the participants associated with stress, the source of which was an IQ test with assignments in physics, mathematics and logics.
Strictly speaking, they didn’t have to use tea in this experiment. Calmness is induced by calories. It’s all about the compensation for energy loss caused by the stress. Besides, it’s very difficult to imagine a person who would be soothed by instant unsweetened tea. Maybe only if he or she had seven legs of different colors.