Examples from literature

• Caffeine wakes us up and gives us energy. 
• Many people like tea and coffee because of the caffeine in these drinks. 
• Effects of Tea and Coffee. —In addition to the stimulating agent caffeine, tea and coffee contain a bitter, astringent substance, known as tannin. 
• In chemical composition caffeine closely resembles a waste, called uric acid, and in the body is converted into this substance. 
• Tea and coffee contain a drug, called caffeine, which acts upon the nervous system and which may, on this account, interfere with the proper control of the heart. 
• The first trial to combat or prevent this drowsiness was made with caffeine. 
• They are usually so addicted to caffeine, cigarettes, alcohol, and so forth, that when they had fasted, even briefly, their bodies were forced to dip into highly-polluted fat reserves while simultaneously the body begins withdrawal.