Coffee, tea, chocolate and many soft drinks contain caffeine, and it is used to flavor some foods. It also is found in medications for staying awake, dieting and treating colds, allergies, migraines and muscle tension. Caffeine has been a part of the typical daily diet for thousands of years. Americans consume an average of five cups of coffee or an equal amount of caffeine in other drinks and food each day.
Caffeine stimulates the central nervous system.
Its effects range from mild alertness to heightened anxiety and body tension. It shortens reaction time among some users. But its impact on creativity and other intellectual activities is hard to define. Caffeine can be habit-forming. How caffeine affects you depends on what and how much you drink.