question: How and in what way does caffeine energize the human body and why are so many people addicted to it?
comment: Caffeine doesn't give energy; it binds to the chemoreceptors in the brain for adenosine, which is what makes you feel sleepy. By binding to that chemoreceptor, it prevents adenosine from doing so, therefore preventing you from *feeling* tired. Any caffeinated thing you eat/drink that gives you energy does so by other means, such as sugar.
passages: Caffeine is the most widely consumed stimulant in North America. Caffeine causes the release of epinephrine from the adrenal medulla. In small doses, caffeine can improve endurance. Recently, it has also been shown to delay the onset of fatigue in exercise. The most probable mechanism for the delay of fatigue is through the obstruction of adenosine receptors in the central nervous system. Adenosine is a neurotransmitter that decreases arousal and increases sleepiness. By preventing adenosine from acting, caffeine removes a factor that promotes rest and delays fatigue.
  
  Section::::Manipulation.:Carbohydrates.
   Caffeine is a central nervous system stimulant that reduces fatigue and drowsiness. At normal doses, caffeine has variable effects on learning and memory, but it generally improves reaction time, wakefulness, concentration, and motor coordination. The amount of caffeine needed to produce these effects varies from person to person, depending on body size and degree of tolerance. The desired effects arise approximately one hour after consumption, and the desired effects of a moderate dose usually subside after about three or four hours.
   Caffeine dependence
  
  Caffeine is a commonplace central nervous system stimulant drug which occurs in nature as part of the coffee, tea, yerba mate and other plants. It is also an additive in many consumer products, most notably beverages advertised as energy drinks and colas.
   Caffeine citrate
  
  Caffeine citrate, sold under the trade name Cafcit among others, is a medication used to treat a lack of breathing in premature babies. Specifically it is given to babies who are born at less than 35 weeks or weight less than once other causes are ruled out. It is given by mouth or slow injection into a vein.
   Caffeine is a proven ergogenic aid in humans. Caffeine improves athletic performance in aerobic (especially endurance sports) and anaerobic conditions. Moderate doses of caffeine (around 5 mg/kg) can improve sprint performance, cycling and running time trial performance, endurance (i.e., it delays the onset of muscle fatigue and central fatigue), and cycling power output. Caffeine increases basal metabolic rate in adults.
   In the absence of caffeine and when a person is awake and alert, little adenosine is present in (CNS) neurons. With a continued wakeful state, over time adenosine accumulates in the neuronal synapse, in turn binding to and activating adenosine receptors found on certain CNS neurons; when activated, these receptors produce a cellular response that ultimately increases drowsiness. When caffeine is consumed, it antagonizes adenosine receptors; in other words, caffeine prevents adenosine from activating the receptor by blocking the location on the receptor where adenosine binds to it. As a result, caffeine temporarily prevents or relieves drowsiness, and thus maintains or restores alertness.
   Section::::Use.:Specific populations.:Pregnancy and breastfeeding.
   Caffeine
  
  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.
   The consumption of caffeinated drinks is often intended entirely or partly for the physical and mental effects of caffeine. Examples include the consumption of tea or coffee with breakfast in many westernized societies, in order to 'wake oneself up', or the deliberate consumption of energy drinks by students wishing to study through the night, or revellers seeking to maintain an alert attitude during social recreation. Caffeine can cause a physical dependence, if consumed in excessive amounts. The need for caffeine can be identified when individuals feel headaches, fatigue and muscle pain 24 hours after their last energy drink.
   Caffeine is a bio-active ingredient found in commonly consumed beverages such as coffee, tea, and sodas. Short-term physiological effects of caffeine include increased blood pressure and sympathetic nerve outflow. Habitual consumption of caffeine may inhibit physiological short-term effects. Consumption of caffeinated espresso increases parasympathetic activity in habitual caffeine consumers; however, decaffeinated espresso inhibits parasympathetic activity in habitual caffeine consumers. It is possible that other bio-active ingredients in decaffeinated espresso may also contribute to the inhibition of parasympathetic activity in habitual caffeine consumers.
   Caffeine improves muscular strength and power, and may enhance muscular endurance. Caffeine also enhances performance on anaerobic tests. Caffeine consumption before constant load exercise is associated with reduced perceived exertion. While this effect is not present during exercise-to-exhaustion exercise, performance is significantly enhanced. This is congruent with caffeine reducing perceived exertion, because exercise-to-exhaustion should end at the same point of fatigue. Caffeine also improves power output and reduces time to completion in aerobic time trials, an effect positively (but not exclusively) associated with longer duration exercise.
  
  Section::::Use.:Specific populations.
  
  Section::::Use.:Specific populations.:Adults.
   Section::::Interactions.:Tobacco.
  
  Smoking tobacco increases caffeine clearance by 56%.
  
  Section::::Interactions.:Birth control.
  
  Birth control pills can extend the half-life of caffeine, requiring greater attention to caffeine consumption.
  
  Section::::Interactions.:Medications.
  
  Caffeine sometimes increases the effectiveness of some medications, such as those for headaches. Caffeine was determined to increase the potency of some over-the-counter analgesic medications by 40%.
  
  The pharmacological effects of adenosine may be blunted in individuals taking large quantities of methylxanthines like caffeine.
  
  Section::::Pharmacology.
  
  Section::::Pharmacology.:Pharmacodynamics.
   Caffeine is used in:
  
  BULLET::::- Bronchopulmonary dysplasia in premature infants for both prevention and treatment. It may improve weight gain during therapy and reduce the incidence of cerebral palsy as well as reduce language and cognitive delay. On the other hand, subtle long-term side effects are possible.
  
  BULLET::::- Apnea of prematurity as a primary treatment, but not prevention.
  
  BULLET::::- Orthostatic hypotension treatment.
   Caffeine can delay or prevent sleep and improves task performance during sleep deprivation. Shift workers who use caffeine make fewer mistakes due to drowsiness.
  
  A systematic review and meta-analysis from 2014 found that concurrent caffeine and -theanine use has synergistic psychoactive effects that promote alertness, attention, and task switching; these effects are most pronounced during the first hour post-dose.
  
  Section::::Use.:Enhancing performance.:Physical.
   Caffeine's mechanism of action is somewhat different from that of cocaine and the substituted amphetamines; caffeine blocks adenosine receptors A and A2A. Adenosine is a by-product of cellular activity, and stimulation of adenosine receptors produces feelings of tiredness and the need to sleep. Caffeine's ability to block these receptors means the levels of the body's natural stimulants, dopamine and norepinephrine, continue at higher levels.
  
  The "Diagnostic and Statistical Manual of Mental Disorders" describes four caffeine-related disorders including intoxication, withdrawal, anxiety, and sleep.
  
  Section::::Dependence.
   Because caffeine is both water- and lipid-soluble, it readily crosses the blood–brain barrier that separates the bloodstream from the interior of the brain. Once in the brain, the principal mode of action is as a nonselective antagonist of adenosine receptors (in other words, an agent that reduces the effects of adenosine). The caffeine molecule is structurally similar to adenosine, and is capable of binding to adenosine receptors on the surface of cells without activating them, thereby acting as a competitive antagonist.
   Caffeine is a stimulant compound belonging to the xanthine class of chemicals naturally found in coffee, tea, and (to a lesser degree) cocoa or chocolate. It is included in many soft drinks, as well as a larger amount in energy drinks. Caffeine is the world's most widely used psychoactive drug and by far the most common stimulant. In North America, 90% of adults consume caffeine daily. A few jurisdictions restrict its sale and use. Caffeine is also included in some medications, usually for the purpose of enhancing the effect of the primary ingredient, or reducing one of its side-effects (especially drowsiness). Tablets containing standardized doses of caffeine are also widely available.
   Side effects can include problems feeding, increased heart rate, low blood sugar, necrotizing enterocolitis, and kidney problems. Testing blood caffeine levels is occasionally recommended. It is a citric acid salt of caffeine. Caffeine citrate is in the xanthine family of medication. It works by stimulating the respiratory centers in the brain.
  
  Caffeine was discovered in 1819. It is on the World Health Organization's List of Essential Medicines, the most effective and safe medicines needed in a health system. In the United Kingdom a 10 mg vial costs £4.90. The intravenous form may also be taken by mouth.
  
  Section::::Medical uses.
   Mild physical dependence can result from excessive caffeine intake. Caffeine addiction, or a pathological and compulsive form of use, has not been documented in humans.
   Tablets offer several advantages over coffee, tea, and other caffeinated beverages, including convenience, known dosage, and avoidance of concomitant intake of sugar, acids, and fluids. Manufacturers of caffeine tablets claim that using caffeine of pharmaceutical quality improves mental alertness. These tablets are commonly used by students studying for their exams and by people who work or drive for long hours.
  
  Section::::Products.:Other oral products.
   Caffeine can have both positive and negative health effects. It can treat and prevent the premature infant breathing disorders bronchopulmonary dysplasia of prematurity and apnea of prematurity. Caffeine citrate is on the WHO Model List of Essential Medicines. It may confer a modest protective effect against some diseases, including Parkinson's disease. Some people experience sleep disruption or anxiety if they consume caffeine, but others show little disturbance. Evidence of a risk during pregnancy is equivocal; some authorities recommend that pregnant women limit consumption to the equivalent of two cups of coffee per day or less. Caffeine can produce a mild form of drug dependence – associated with withdrawal symptoms such as sleepiness, headache, and irritability – when an individual stops using caffeine after repeated daily intake. Tolerance to the autonomic effects of increased blood pressure and heart rate, and increased urine output, develops with chronic use (i.e., these symptoms become less pronounced or do not occur following consistent use).
   Section::::Society and culture.:Consumption.
  
  Global consumption of caffeine has been estimated at 120,000 tonnes per year, making it the world's most popular psychoactive substance. This amounts to one serving of a caffeinated beverage for every person every day.
  
  Section::::Society and culture.:Religions.
   Caffeine is also an ingredient of several medications, many of them over-the-counter and prescription drugs. The consensus is to consider caffeine a drug with pharmacological effects acting throughout the body.
  
  Section::::Signs and symptoms.
   Death can occur when a person had a caffeine overdose. The LD of caffeine in humans is dependent on individual sensitivity, but is estimated to be 150–200 milligrams per kilogram of body mass (75–100 cups of coffee for a 70 kilogram adult). A number of fatalities have been caused by overdoses of readily available powdered caffeine supplements, for which the estimated lethal amount is less than a tablespoon. The lethal dose is lower in individuals whose ability to metabolize caffeine is impaired due to genetics or chronic liver disease A death was reported in a man with liver cirrhosis who overdosed on caffeinated mints.
   Caffeine can be quantified in blood, plasma, or serum to monitor therapy in neonates, confirm a diagnosis of poisoning, or facilitate a medicolegal death investigation. Plasma caffeine levels are usually in the range of 2–10 mg/L in coffee drinkers, 12–36 mg/L in neonates receiving treatment for apnea, and 40–400 mg/L in victims of acute overdosage. Urinary caffeine concentration is frequently measured in competitive sports programs, for which a level in excess of 15 mg/L is usually considered to represent abuse.
  
  Section::::Chemistry.:Analogs.
  
presuppositions: Caffeine provides energy to the human body. Caffein energize human body.
corrections: Caffeine does not provide energy to the human body but rather prevents the chemical receptor for sleepiness from making you feel tired. Caffein doesn’t give energy, instead it prevents you from feeling tired.
raw_presuppositions: Caffeine provides energy to the human body. Caffein energize human body.
raw_corrections: Caffeine does not provide energy to the human body but rather prevents the chemical receptor for sleepiness from making you feel tired. Caffein doesn’t give energy, instead it prevents you from feeling tired.