Caffeine is a substance present in many products, including coffee, tea, carbonated beverages, chocolate and even some medicines taken for headaches. According to the National Institutes of Health, most people tolerate up to 300mg of caffeine, equal to two to four cups of coffee, without experiencing side effects. However, excessive use can produce certain physical and psychological effects. Following ingestion, caffeine enters the bloodstream and activates areas of the brain that produce several behavioral effects.
STIMULATION
After drinking a cup of coffee, the caffeine jolt can enhance mental alertness and stimulate energy. Caffeine stimulates the release of adrenaline, a hormone responsible for the "fight or flight" response needed when an emergency arises. Effects include increases in heart rate, blood pressure and blood sugar levels to provide extra energy. Excessive caffeine use thus puts the body in a constant state of emergency, causing people to become irritable and jumpy.
ADDICTION
According to "How the Body Works," an encyclopedia of anatomy, caffeine belongs to a group of drugs called central nervous system stimulants, which includes nicotine and cocaine. Though its effects are not as powerful as those of cocaine, the addictive nature of caffeine is similar. Over long terms of consumption, a person becomes addicted, often unknowingly, and experiences withdrawal effects if they stop caffeine intake. Once the adrenaline from coffee wears off and feelings of fatigue come on, they reach for another cup, continually feeding the cycle of addiction.
PLEASURE
Caffeine produces pleasure effects on a neurological level. When ingested caffeine in the bloodstream reaches the brain, the stimulant increases levels of dopamine, a neurotransmitter responsible for activating the brain's pleasure center. Caffeine withdrawal may also produce mild levels of depression partly due to this fact.
REFERENCES
Caffeine
"How the Body Works"; Dr. Peter Abrahams