Caféine

Caféine is a central nervous system (CNS) stimulant of the methylxanthine class. It is the world's most widely consumed psychoactive drug. Unlike many other psychoactive substances, it is legal and unregulated in nearly all parts of the world. There are several known mechanisms of action to explain the effects of caffeine. The most prominent is that it reversibly blocks the action of adenosine on its receptor and consequently prevents the onset of drowsiness induced by adenosine. Caffeine also stimulates certain portions of the autonomic nervous system.

Sources

Caffeine is found in various plants, where it acts as a natural pesticide that paralyzes and kills certain insects feeding on the plants. The most well-known sources of caffeine are the coffee bean, tea leaves, kola nuts, and cacao pods. These sources are used to produce beverages such as coffee, tea, soft drinks, and energy drinks.

Pharmacology

Caffeine is absorbed by the stomach and small intestine within 45 minutes of ingestion. It is then distributed throughout all tissues of the body. The half-life of caffeine varies widely among individuals according to factors such as age, liver function, pregnancy, some concurrent medications, and the level of enzymes in the liver needed for caffeine metabolism.

Mechanism of Action

Caffeine acts as a nonselective antagonist of adenosine receptors. By blocking adenosine receptors, caffeine prevents the inhibitory effects of adenosine on the CNS, leading to increased neuronal activity and the release of other neurotransmitters such as dopamine and norepinephrine.

Effects

Caffeine has both positive and negative effects on human health. It can improve alertness, concentration, and performance on cognitive tasks. However, excessive consumption can lead to caffeine addiction, insomnia, nervousness, restlessness, stomach irritation, nausea, and vomiting.

Health Benefits

Moderate caffeine consumption has been associated with a lower risk of several diseases, including Parkinson's disease, Alzheimer's disease, and certain types of cancer. It may also improve physical performance and aid in weight loss.

Adverse Effects

High doses of caffeine can lead to caffeine intoxication, which may cause symptoms such as anxiety, tremors, tachycardia, and in severe cases, seizures. Chronic high consumption can lead to caffeine dependence and withdrawal symptoms such as headache, fatigue, and irritability.

Cultural Impact

Caffeine consumption is deeply ingrained in many cultures around the world. Coffeehouses and tea houses have historically been important social and cultural hubs. In modern times, the popularity of energy drinks and specialty coffee has further cemented caffeine's role in contemporary society.

Regulation

While caffeine is legal and unregulated in most parts of the world, some countries have set limits on the amount of caffeine that can be included in certain products. For example, the European Union has regulations on the labeling of high-caffeine beverages.

See Also

• Coffee
• Tea
• Energy drink
• Soft drink
• Caffeine dependence
• Caffeine intoxication