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Coffee and tea are among the most popular beverages worldwide and contain substantial amounts of caffeine, making caffeine the most widely consumed psychoactive agent.1 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 to make an herbal tea), and guarana berries (used in various beverages and supplements).1,2 Caffeine can also be synthesized and is added to foods and beverages, including soft drinks, energy drinks, and energy shots, and to tablets marketed for reducing fatigue.2 In addition, caffeine is widely used as a treatment for apnea of prematurity in infants,3 and caffeine and analgesic agents are used together in pain medications.4
Coffee and tea have been consumed for hundreds of years and have become an important part of cultural traditions and social life.5 In addition, people use coffee beverages to increase wakefulness and work productivity. The caffeine content of commonly used sources of caffeine is shown in Table 1. For a typical serving, the caffeine content is highest in coffee, energy drinks, and caffeine tablets; intermediate in tea; and lowest in soft drinks. In the United States, 85% of adults consume caffeine daily,6 and average caffeine intake is 135 mg per day, which is equivalent to about 1.5 standard cups of coffee (with a standard cup defined as 8 fluid oz [235 ml]).7 Coffee is the predominant source of caffeine ingested by adults, whereas soft drinks and tea are more important sources of caffeine ingested by adolescents (Figure 1).
Concerns have long existed that coffee and caffeine may increase the risks of cancer and cardiovascular diseases, but more recently, evidence of health benefits has also emerged.8 A key issue in research on caffeine and coffee is that coffee contains hundreds of other biologically active phytochemicals, including polyphenols such as chlorogenic acid and lignans, the alkaloid trigonelline, melanoidins formed during roasting, and modest amounts of magnesium, potassium, and vitamin B3 (niacin).8 These coffee compounds may reduce oxidative stress,9 improve the gut microbiome,10 and modulate glucose and fat metabolism.11,12 In contrast, the diterpene cafestol, which is present in unfiltered...