Tea connoisseurs and producers recommend drinking this beverage freshly brewed. And it’s not just that this brings out the tea’s flavor and aroma better. If the tea is left exposed to the air for several hours, bacteria and harmful compounds begin to form as a result of exposure to oxygen. On the surface of the tea, these appear as a thick, dark film that leaves a residue on the cup. These substances have the most damaging effect on the organs of the gastrointestinal tract, primarily the liver. The Japanese consider tea that has sat for a day to be “worse than a snake bite,” while the Chinese compare it to poison.