Caffeine is a chemical found in a number of foods and beverages, including black tea, coffee, chocolate, some sodas and energy drinks. A small organic molecule, ingested caffeine is absorbed into the bloodstream from the digestive tract. It then circulates and signals to a number of cells and tissues. Exposure to caffeine can have a number of chemical effects throughout the body.
Adenosine Blocking
One major chemical effect of caffeine is blocking the function of another chemical in the brain, adenosine. Under normal circumstances, adenosine binds to small proteins called receptors, which are found on nerve cells in the brain. The University of Minnesota explains that when adenosine binds to its receptor in specific parts of the brain, this leads to a feeling of sleepiness and drowsiness. Caffeine prevents adenosine from binding to its receptor, and therefore inhibits drowsiness, leading to an increase in energy and alertness after ingesting caffeine. As the caffeine is metabolized in the body, this effect wears off, leading to the "crash" after caffeine ingestion.
Increased Dopamine
Caffeine also has the chemical effect of increasing dopamine signaling in the brain after consumption. Dopamine belongs to a family of chemicals called neurotransmitters, which function as signaling molecules that allow nerve cells to communicate with each other. Dopamine signaling affects mood regulation, with increased dopamine signaling leading to enhanced mood. Western Washington University explains that this dopamine release leads to a feeling of pleasure after the ingestion of caffeine, and indicates that this dopamine signaling allows caffeine to act as a mild pain-killer. Consuming a moderate amount of caffeine may help diminish pain or discomfort, and caffeine may help relieve a headache.
Genetic Mutations
One potentially negative chemical effect of caffeine is an increased rate of genetic mutation in cells exposed to the chemical. The human genome -- the whole of a person's DNA -- contains a sequence of 3 billion chemicals called nucleotides that form genes. Caffeine's chemical structure is similar to that of specific nucleotides, and the chemical can occasionally get incorporated into the cell's DNA. This incorporation increases the rate of genetic mutations in the cell, explains a study published in "Teratology" in 2005. Limiting caffeine exposure to one or two cups of coffee or tea a day can help prevent over-exposure and limit your cells' exposure to the chemical, preventing excessive genetic mutations in your cells.
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