Caffeine is a central nervous system stimulant that increases feelings of alertness and excitement in the brain and body. It also has a mild diuretic effect–it causes the body to release fluids in urination. Only a few plants and berries contain caffeine naturally, but those foods–and therefore their caffeine–can sometimes be found in other recipes and prepared foods.
Coffee Beans and Tea Leaves
Coffee beans and tea leaves used to make coffee and tea are probably the most common source of caffeine in the American diet. The amount of caffeine in these drinks can vary depending on the type of coffee and tea and the roasting time of the beans or leaves. A typical 8-ounce cup of brewed coffee can contain between 95 and 200 milligrams of caffeine, while an 8-ounce cup of black tea has between 40 and 120 milligrams. Green tea is a lower-caffeine option, with about 26 milligrams of caffeine per 6-ounce cup. Small amounts of coffee and tea are used as a flavoring in some desserts and sauces. Caffeine content will vary between recipes.
Cocoa Beans and Chocolate
Cocoa beans, the main ingredient in chocolate and cocoa powder, contain a small amount of caffeine. The exact amount in chocolate depends on the type and roast of the beans. A 40-gram milk chocolate bar can contain between 2 and 23 milligrams of caffeine. Dark chocolate is slightly higher in caffeine, with between 5 and 35 milligrams per 28-gram bar. Chocolate is used in many desserts and snacks and some savory recipes, such as the Mexican sauce called mole. Because the overall caffeine content of chocolate is relatively low, caffeine levels in such foods are also much lower than a typical cup of coffee.
Soft Drinks
Traditionally used as a digestive aid and stimulant in its native Africa, the kola nut is best known in the United States for its role in cola-flavored soft drinks like Coke and Pepsi. The kola nut naturally contains caffeine. However, most of the caffeine in soft drinks is synthetic, added during the manufacturing process. Colas, Dr. Pepper, Mello Yello and Mountain Dew are particularly high in caffeine, with between 35 and 54 milligrams of caffeine per 12-ounce drink. Energy drinks like Red Bull have even more. Eight ounces of Red Bull contains 76 milligrams of caffeine, making it comparable to a cup of coffee.
Guarana
Caffeine-rich guarana berries are used as an ingredient in some energy drinks and are marketed as an herbal treatment for fatigue and sexual dysfunction and as an appetite suppressant. The amount of caffeine in guarana drinks or supplements varies between products, but is high enough that the Memorial Sloan-Kettering Cancer Center warns against consuming guarana with other caffeine-rich foods and drinks like coffee. Excessive amounts of caffeine can lead to rapid heartbeat, anxiety, insomnia and in extreme cases, seizures.
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