Caffein

Caffeine.svg

Caffeine 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 leaf, kola nut, and cacao pod. These sources are used to produce beverages such as coffee, tea, soft drinks, and energy drinks.

Effects

Caffeine is known to have both positive and negative effects on human health. It can improve alertness and concentration, reduce fatigue, and enhance cognitive function. However, excessive consumption can lead to insomnia, nervousness, restlessness, stomach irritation, nausea, increased heart rate, and other side effects.

Pharmacology

Caffeine is rapidly absorbed from the gastrointestinal tract and distributed throughout the body. It crosses the blood-brain barrier and exerts its effects on the CNS. The half-life of caffeine varies widely among individuals, influenced by factors such as age, liver function, pregnancy, and concurrent use of other drugs.

Metabolism

Caffeine is metabolized in the liver by the cytochrome P450 oxidase enzyme system, primarily by the enzyme CYP1A2. The main metabolites of caffeine are paraxanthine, theobromine, and theophylline, each of which has its own effects on the body.

Health Considerations

Moderate caffeine consumption is generally considered safe for most people. However, certain populations, such as pregnant women, individuals with certain medical conditions, and those sensitive to caffeine, should limit their intake. The FDA recommends a maximum daily intake of 400 milligrams for most adults.

See also

• Coffee
• Tea
• Energy drink
• Soft drink
• Theobromine
• Theophylline
• Adenosine receptor

Related pages

• Central nervous system
• Stimulant
• Psychoactive drug
• Adenosine
• Autonomic nervous system
• Cytochrome P450
• Liver