Coffee and tea are among the most popular beverages worldwide and contain substantial amounts of caffeine, making caffeine the most widely consumed psychoactive agent. A variety of plants contain caffeine in their seeds, fruits, and leaves. Besides coffee and tea, these plants include cacao beans (an ingredient of chocolate), yerba matte leaves (used in herbal tea), and guarana berries (used in various beverages and supplements). Caffeine can be synthesized and is added to foods and beverages, including soft drinks, energy drinks, energy shots, and tablets sold to reduce fatigue. Caffeine and analgesics are used together in some pain medications, for example headache medications.
Coffee and tea have been consumed for hundreds of years and