section_path: Chemical composition
section_name: Chemical composition
paragraph_text: Chemical composition
  
  Physically speaking, tea has properties of both a solution and a suspension. It is a solution of the water-soluble compounds extracted from the tea leaves, such as the polyphenols and amino acids. Tea infusions are among most consumed beverages globally.
  
  Caffeine makes up about 3% of tea's dry weight, which translates to between 30 and 90 milligrams per 250-millilitre (8 + 1 ⁄ 2 US fl oz) cup depending on the type, brand, and brewing method. A study found that the caffeine content of one gram of black tea ranged from 22 to 28 mg, while the caffeine content of one gram of green tea ranged from 11 to 20 mg, reflecting a significant difference. Tea contains small amounts of theobromine and theophylline, which are xanthines and stimulants, similar to caffeine.
  
  The astringency in tea can be attributed to the presence of polyphenols. These are the most abundant compounds in tea leaves, making up 30–40% of their composition. Polyphenols in tea include flavonoids, epigallocatechin gallate (EGCG), and other catechins. Although there has been preliminary clinical research on whether green or black teas may protect against various human diseases, there is no evidence that tea polyphenols have any effect on health or lowering disease risk.