Caffeine

caffeinatedHealth effects of caffeineNo-DozguaranineTheinecaffeine pillscaffeine withdrawalcaffeine-freecoffeeIntoxication
Caffeine is a central nervous system (CNS) stimulant of the methylxanthine class.wikipedia
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Tea

tea plantationtea leavestea garden
Caffeine-containing drinks, such as coffee, tea, and cola, are very popular; as of 2014, 85% of American adults consumed some form of caffeine daily, consuming 164 mg on average.
Tea has a stimulating effect in humans primarily due to its caffeine content.

Coffea

coffeecoffee plantscoffee plant
The most well-known source of caffeine is the coffee bean, a misnomer for the seed of Coffea plants.
The fruits, like the seeds, contain a large amount of caffeine, and have a distinct sweet taste and are often juiced.

Coffee

coffee beansblack coffeegourmet coffee
Caffeine-containing drinks, such as coffee, tea, and cola, are very popular; as of 2014, 85% of American adults consumed some form of caffeine daily, consuming 164 mg on average.
Coffee is darkly colored, bitter, slightly acidic and has a stimulating effect in humans, primarily due to its caffeine content.

Cola

cola-flavouredclear colaDiet cola
Caffeine-containing drinks, such as coffee, tea, and cola, are very popular; as of 2014, 85% of American adults consumed some form of caffeine daily, consuming 164 mg on average.
Most contain caffeine, which was originally sourced from the kola nut, leading to the drink's name, though other sources are now also used.

Coffee bean

coffeecoffee beansgreen coffee
The most well-known source of caffeine is the coffee bean, a misnomer for the seed of Coffea plants.
Arabica beans consist of 0.8–1.4% caffeine and Robusta beans consist of 1.7–4% caffeine.

Psychoactive drug

psychoactivepsychotropicdrug
It is the world's most widely consumed psychoactive drug.
Caffeine is the world's most widely consumed psychoactive substance, but unlike many others, it is legal and unregulated in nearly all jurisdictions.

Alkaloid

alkaloidspurine alkaloidalkaloid biosynthesis
Caffeine is a bitter, white crystalline purine, a methylxanthine alkaloid, and is chemically related to the adenine and guanine bases of deoxyribonucleic acid (DNA) and ribonucleic acid (RNA).
Other alkaloids possess psychotropic (e.g. psilocin) and stimulant activities (e.g. cocaine, caffeine, nicotine, theobromine), and have been used in entheogenic rituals or as recreational drugs.

Insomnia

trouble sleepingsleeplessnessdifficulty sleeping
Some people experience sleep disruption or anxiety if they consume caffeine, but others show little disturbance.
Conditions that can result in insomnia include psychological stress, chronic pain, heart failure, hyperthyroidism, heartburn, restless leg syndrome, menopause, certain medications, and drugs such as caffeine, nicotine, and alcohol.

Espresso

cremaEspresso Coffeecafecito
A cup of coffee contains 80–175 mg of caffeine, depending on what "bean" (seed) is used and how it is prepared (e.g., drip, percolation, or espresso).
Espresso has more caffeine per unit volume than most coffee beverages, but because the usual serving size is much smaller, the total caffeine content is less than a mug of standard brewed coffee, contrary to a common belief.

Caffeine-induced anxiety disorder

Caffeine-induced anxiety disorder is a subclass of the DSM-5 diagnosis of substance/medication-induced anxiety disorder.
Consumption of caffeine has long been linked to anxiety.

Performance-enhancing substance

performance-enhancing drugsperformance-enhancing drugimprove physique and performance
Caffeine is a proven ergogenic aid in humans.
As is usual with categorization, there are borderline cases; caffeine, for example, is considered a performance enhancer by some but not others.

Caffeine dependence

caffeinecaffeine addictioncoffee addiction
The ICD-11 includes caffeine dependence as a distinct diagnostic category, which closely mirrors the DSM-5’s proposed set of criteria for “caffeine-use disorder”.
Caffeine is a commonplace central nervous system stimulant drug which occurs in nature as part of the coffee, tea, yerba mate, cocoa and other plants.

Adenosine

Aadenosine analogAdenoscan
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.
Methylxanthines (e.g., caffeine, found in coffee, or theophylline in tea, or theobromine, as found in chocolate) competitively antagonize adenosine's effects; an increased dose of adenosine may be required.

Caffeinism

Consumption of 1 – per day is associated with a condition known as caffeinism . Caffeinism usually combines caffeine dependency with a wide range of unpleasant symptoms including nervousness, irritability, restlessness, insomnia, headaches, and palpitations after caffeine use.
Caffeinism is a state of intoxication due to excessive consumption of caffeine.

Caffeine citrate

Cafcit
Caffeine citrate is on the WHO Model List of Essential Medicines.
Testing blood caffeine levels is occasionally recommended.

CYP1A2

1A2cytochrome p-450 cyp1a22
Caffeine is a substrate for CYP1A2, and interacts with many substances through this and other mechanisms.
Other xenobiotic substrates for this enzyme include caffeine, aflatoxin B1, and paracetamol (acetaminophen).

Drink

beveragebeveragesdrinks
Beverages containing caffeine are ingested to relieve or prevent drowsiness and to improve performance.
Sleep beverages, nightcaps, and relaxation drinks have been known to contain other natural ingredients and are usually free of caffeine and alcohol but some have claimed to contain marijuana.

Osteoporosis

bone lossosteoporoticpostmenopausal osteoporosis
In postmenopausal women, high caffeine consumption can accelerate bone loss.
Caffeine is not a risk factor for osteoporosis.

Sleep

sleepingsleep architectureasleep
Caffeine can delay or prevent sleep and improves task performance during sleep deprivation.
Coffee and caffeine temporarily block the effect of adenosine, prolong sleep latency, and reduce total sleep time and quality.

Glaucoma

open-angle glaucomaangle closure glaucomaacute angle-closure glaucoma
Caffeine increases intraocular pressure in those with glaucoma but does not appear to affect normal individuals.
Caffeine increases intraocular pressure in those with glaucoma, but does not appear to affect normal individuals.

Adenosine receptor

adenosine receptorsP1P1 receptors
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.
The adenosine receptors are commonly known for their antagonists caffeine and theophylline, whose action on the receptors produces the stimulating effects of coffee, tea and chocolate.

Purine

purinespu'''R'''ineTraube purine synthesis
Caffeine is a bitter, white crystalline purine, a methylxanthine alkaloid, and is chemically related to the adenine and guanine bases of deoxyribonucleic acid (DNA) and ribonucleic acid (RNA).
Other notable purines are hypoxanthine (4), xanthine (5), theobromine (6), caffeine (7), uric acid (8) and isoguanine (9).

Miscarriage

miscarriedspontaneous abortionmiscarriages
A 2011 review found that caffeine during pregnancy does not appear to increase the risk of congenital malformations, miscarriage or growth retardation even when consumed in moderate to high amounts.
Caffeine consumption also has been correlated to miscarriage rates, at least at higher levels of intake.

Apnea of prematurity

Apnea monitorinfant apnealack of breathing in premature babies
It can treat and prevent the premature infant breathing disorders bronchopulmonary dysplasia of prematurity and apnea of prematurity.
Methylxanthines (theophylline and caffeine) have been used for almost three decades to treat apnea of prematurity.

Parkinson's disease

ParkinsonParkinson’s diseaseParkinson disease
It may confer a modest protective effect against some diseases, including Parkinson's disease.
Caffeine also appears protective with a greater decrease in risk occurring with a larger intake of caffeinated beverages such as coffee.