Caffeine is a stimulant that activates the central nervous system, resulting in a boost in energy, an altered metabolism and greater alertness. Ingesting an excess of 1,000 mg of caffeine per day can make the user irritable, restless and anxious. Larger quantities over extended periods can cause sleeplessness, headaches and an abnormal heartbeat. Continued use can also result in addiction; accordingly, cessation of caffeine use after regular consumption can cause withdrawal.
Warm Drinks
Coffee is the most common and well-known source of caffeine. This includes regular coffee and other coffee drinks, such as caffe americano, mocha, espresso and latte. In addition to coffee, most teas contain caffeine, including green tea, black tea and Chai tea. Hot cocoa also contains caffeine, although it usually contains roughly 10 percent of that found in coffee or tea.
Cold Drinks
A rather wide variety of cold drinks contain caffeine, including iced coffee, blended iced coffee, iced tea, and ice creams flavored with tea or coffee. However, a single serving of ice creams typically contain 10 to 12 percent of the caffeine contained in a single serving of their sources. Most canned or bottled teas, coffees and chocolate milks also contain caffeine in variable amounts that range from moderate to negligible. Many sodas like cola, root beer and orange contain caffeine. Energy drinks usually contain caffeine in amounts comparable to that found in coffee and tea.
Candy
Some candies contain caffeine, such as chocolate bars and candy bars including chocolate. Moreover, as of 2010, a number of candies are available that advertise energy supplementation. These candies contain added caffeine and include jelly beans, jaw breakers, chewing gum, mints and chocolate bars. Most candies that advertise energy boosts provide anywhere from 50 to 100 percent of the caffeine contained in a typical cup of brewed coffee.
Miscellaneous
Caffeinated versions of various foods are available on the market as of 2010. These include sunflower seeds, chocolate milk, oatmeal and beer. In addition, various drugs contain caffeine, some as a primary active ingredient and others as a secondary ingredient. For example, a headache medication may contain caffeine to help relieve a headache more quickly. Alternately, various pills containing mostly caffeine are available as energy supplementation or temporary sleep replacements.
