kofein

Kofein, or caffeine, is a natural central nervous system stimulant classified as a xanthine alkaloid. Its chemical name is 1,3,7-trimethylxanthine. It occurs naturally in coffee beans, tea leaves, cacao beans, kola nuts, and some other plants, and is widely added to a variety of beverages and medicines.

In humans, caffeine is rapidly absorbed after ingestion and distributed throughout the body. It acts mainly by antagonizing adenosine receptors A1 and A2A, reducing drowsiness and increasing alertness. It also increases release of neurotransmitters such as dopamine and norepinephrine, and can enhance exercise performance modestly.

Pharmacokinetics: Metabolized in the liver by cytochrome P450 1A2 to paraxanthine, theobromine, and theophylline. The elimination half-life is about 3-5 hours in healthy adults, longer in pregnancy and in certain medications, shorter in smokers.

Health effects: Short-term effects include improved attention and mood, increased heart rate and diuresis, and potential insomnia or jitters at higher doses. Chronic high intake can lead to dependence and withdrawal symptoms such as headaches and fatigue when stopped.

Safety and consumption: Commonly consumed in moderate amounts, up to 400 mg per day for healthy adults is considered acceptable by many health authorities; pregnant individuals are generally advised to limit intake to around 200 mg per day. Excessive intake may cause anxiety, palpitations, upset stomach, or caffeine toxicity in rare cases.

Common sources and caffeine content vary: an 8-ounce cup of brewed coffee contains roughly 70-95 mg; tea 20-60 mg; an espresso shot about 60-75 mg; cola beverages 25-40 mg per 12 oz; energy drinks often 80-160 mg per serving.