Appropriate consumption of black tea can replenish nutrients for the organism, and drinking large quantities of black tea for a long time may cause some harm to the body’s digestive system, nervous system and so on. Black tea belongs to one of the six major types of tea, belongs to the post-fermented tea, which is a kind of tea made by utilizing bacterial fermentation. 1. Digestive system: the ellagic acid in black tea combines with the protein in food, which may cause indigestion and constipation. 2. Nervous system: black tea contains a certain amount of caffeine, caffeine is easy to cause cerebral cortex excitation, so long-term drinking of black tea is easy to trigger difficulty in falling asleep, insomnia and so on. Often drink black tea can also lead to insomnia and other excitement, because black tea contains a large amount of tannins and a variety of active substances, which can easily lead to insomnia and other symptoms of excitement, so in our daily lives, you can drink, but try not to drink a large amount of black tea for a long time.