Caffeine is a central nervous system (CNS) stimulant that is found in natural sources such as coffee, tea, and soda. When ingested, caffeine increases alertness, causes reduced drowsiness, and counteracts performance decline associated with sleep deprivation. Most adults can consume up to 400 milligrams (mg) of caffeine a day without experiencing negative side effects.
The amount of caffeine in a cup of coffee depends on how the beans were roasted, how finely they were ground, how long they were brewed, and the size of the cup. A typical 8-ounce cup of home-brewed coffee contains between 80 and 150 milligrams (mg) of caffeine; a 12-ounce serving of drip-brewed or instant coffee contains about 100 mg, and an 8-ounce serving of tea contains about 50 mg. Soft drinks contain significantly more caffeine than coffee: 12 ounces of cola typically have about 35 to 55 mg of caffeine, while an energy drink may contain significantly more—up to 300 mg per can. Caffeine is also found in chocolate and some medications.
The negative effects of too much caffeine include anxiety, insomnia, tremors, irregular heartbeat, muscle tremors, and rhabdomyolysis (the breakdown of skeletal
Caffeine is a stimulant that occurs naturally in over 60 plants, including coffee beans. It is a xanthine alkaloid (a chemical compound), which acts as a central nervous system stimulant.
Caffeine is the world’s most widely consumed psychoactive drug and by far the most common stimulant. Caffeine’s mechanisms of action are not completely understood, but it appears to block the effects of adenosine on neurons.
How much caffeine in coffee
A typical 8-ounce cup of home-brewed coffee contains between 80 and 150 milligrams (mg) of caffeine;
A 12-ounce serving of drip-brewed or instant coffee contains about 100 mg, and an 8-ounce serving of tea contains about 50 mg
Caffeine can be toxic in high doses or with prolonged use. Caffeine also has benefits, and some studies suggest that it may protect against Alzheimer’s disease, Parkinson’s disease, liver injury, and diabetes.