Found in coffee, tea, cola and chocolate, caffeine may be the most popular drug substance in the world. More than 80 percent of American report that they consume caffeine daily. The reason for the country's love of caffeine lies in brain chemistry and, in particular, in the relationship between caffeine and the dopamine.
Role of Dopamine
Dopamine is a neurotransmitter in the brain and plays a role in many brain functions including cognition, movement, memory and learning. It is most commonly associated with the reward system of the brain. Dopamine is released during pleasurable activities and motivates the individual to perform the activity again in the future. Caffeine increases dopamine levels and promotes a feeling of pleasure and well-being. The dopamine connection is one reason individuals become dependent on daily caffeine consumption. Other drugs, including heroin and cocaine, also increase dopamine levels. The effect of caffeine on dopamine is mild, however, compared to these substances.
Additional Effects of Caffeine
In addition to dopamine, caffeine interacts with another neurotransmitter called adenosine. In the brain, adenosine binds to specific receptors and causes neural activity to slow down, promoting sleep. Caffeine binds to the same adenosine receptors but does not slow neural activity. As a result, the body becomes less sensitive to adenosine. Neural activity speeds up and the adrenalin hormones are produced, flooding the body with extra energy.
Amount of Caffeine
A 5 oz. serving of brewed coffee contains 60 to 150 mg caffeine. Decaffeinated coffee contains only 2 to 5 mg per 5 oz. serving. Tea contains 40 to 80 mg, while hot cocoa contains 1 to 8 mg. Chocolate contains 3 to 60 mg caffeine in a 50 g bar. Most individuals can consume 200 to 300 mg caffeine each day, the equivalent of two to four small cups of coffee, without adverse health effects.
Health Issues
The most common health complaint associated with heavy caffeine consumption is sleep disruption. Other symptoms include nervousness, restlessness, irritability and anxiety. Some individuals also experience gastrointestinal problems, rapid or irregular heartbeat, muscle tremors and headache. Caffeine can interact with several common prescription medications including antibiotics and bronchodilators.
Other Considerations
Since caffeine affects the pleasure centers of the brain, many individuals experience discomfort when their caffeine consumption is reduced. Symptoms of caffeine withdrawal include headache, fatigue, listlessness, irritability and difficulty concentrating. If you wish to reduce your consumption of caffeine, make your changes gradually. Drink a smaller cup of coffee or substitute decaffeinated versions until your body adjusts to the lower levels of caffeine.
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