Caffeine, as do other alkaloids such as cinchonine, quinine or strychnine, precipitates polyphenols and tannins. This property can be used in a quantitation method. [ clarification needed] [213] Natural occurrence Roasted coffee beans However, this effect doesn’t seem to occur in everyone. Indeed, even some people with heart problems may be able to tolerate large amounts of caffeine without any adverse effects. One study in 25 healthy men found that those who ingested approximately 300 mg of caffeine experienced more than double the stress of those who took a placebo.

Caffeine tablets are legal and are used to increase alertness. Some beliefs about their effectiveness, for example in improving exam performance, are not wholly supported by the evidence. They do not replace the need for sleep, in fact a nap can be much more beneficial.Common causes of rhabdomyolysis include trauma, infection, drug abuse, muscle strain and bites from poisonous snakes or insects. This is more likely to cause side effects, as a full key down/key up is generated. It's included for compatibility with older systems which might need this EFSA Panel on Dietetic Products, Nutrition and Allergies (2015). "Scientific Opinion on the safety of caffeine". EFSA Journal. 13 (5): 4102. doi: 10.2903/j.efsa.2015.4102. Coffee’s laxative effect has been attributed to the release of gastrin, a hormone the stomach produces that speeds up activity in the colon. What’s more, decaffeinated coffee has been shown to produce a similar response ( 19, 20, 21).

Grimes LM, Kennedy AE, Labaton RS, Hine JF, Warzak WJ (2015). "Caffeine as an Independent Variable in Behavioral Research: Trends from the Literature Specific to ADHD". Journal of Caffeine Research. 5 (3): 95–104. doi: 10.1089/jcr.2014.0032.

Some medical conditions may interact with caffeine. Tell your health care provider if you have ANY medical conditions, especially if any of the following apply to you: If you are pregnant, discuss with your health care provider if caffeine is appropriate for your use.

Until recently, the Seventh-day Adventist Church asked for its members to "abstain from caffeinated drinks", but has removed this from baptismal vows (while still recommending abstention as policy). [282] Some from these religions believe that one is not supposed to consume a non-medical, psychoactive substance, or believe that one is not supposed to consume a substance that is addictive. The Church of Jesus Christ of Latter-day Saints has said the following with regard to caffeinated beverages: "... the Church revelation spelling out health practices (Doctrine and Covenants 89) does not mention the use of caffeine. The Church's health guidelines prohibit alcoholic drinks, smoking or chewing of tobacco, and 'hot drinks' – taught by Church leaders to refer specifically to tea and coffee." [283]Theophylline (4%): Relaxes smooth muscles of the bronchi, and is used to treat asthma. The therapeutic dose of theophylline, however, is many times greater than the levels attained from caffeine metabolism. [46] 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). It is found in the seeds, fruits, nuts, or leaves of a number of plants native to Africa, East Asia and South America, [18] and helps to protect them against herbivores and from competition by preventing the germination of nearby seeds, [19] as well as encouraging consumption by select animals such as honey bees. [20] The best-known source of caffeine is the coffee bean, the seed of the Coffea plant. People may drink beverages containing caffeine to relieve or prevent drowsiness and to improve cognitive performance. To make these drinks, caffeine is extracted by steeping the plant product in water, a process called infusion. Caffeine-containing drinks, such as coffee, tea, and cola, are consumed globally in high volumes. In 2020, almost 10 million tonnes of coffee beans were consumed globally. [21] Caffeine is the world's most widely consumed psychoactive drug. [22] [23] Unlike most other psychoactive substances, caffeine remains largely unregulated and legal in nearly all parts of the world. Caffeine is also an outlier as its use is seen as socially acceptable in most cultures and even encouraged in others. Structure of a typical chemical synapse Caffeine's primary mechanism of action is as an adenosine receptor antagonist in the brain. The differing perceptions in the effects of ingesting beverages made from various plants containing caffeine could be explained by the fact that these beverages also contain varying mixtures of other methylxanthine alkaloids, including the cardiac stimulants theophylline and theobromine, and polyphenols that can form insoluble complexes with caffeine. [219] Products Caffeine content in select food and drugs [220] [221] [222] [223] [224] serious allergic reactions (difficult breathing, chest tightness, swelling of the mouth, face, lips, or tongue, rash, hives, or itching)

Farias-Pereira R, Park CS, Park Y. Mechanisms of action of coffee bioactive components on lipid metabolism. Food Sci Biotechnol. 2019;28(5):1287-1296. doi: 10.1007/s10068-019-00662-0 Caffeine overdose can result in a state of central nervous system overstimulation known as caffeine intoxication, a clinically significant temporary condition that develops during, or shortly after, the consumption of caffeine. [140] This syndrome typically occurs only after ingestion of large amounts of caffeine, well over the amounts found in typical caffeinated beverages and caffeine tablets (e.g., more than 400–500mg at a time). According to the DSM-5, caffeine intoxication may be diagnosed if five (or more) of the following symptoms develop after recent consumption of caffeine: restlessness, nervousness, excitement, insomnia, flushed face, diuresis, gastrointestinal disturbance, muscle twitching, rambling flow of thought and speech, tachycardia or cardiac arrhythmia, periods of inexhaustibility, and psychomotor agitation. [141] Nehlig A. Effects of coffee/caffeine on brain health and disease: what should I tell my patients? Pract Neurol. 2016;16(2):89-95. doi: 10.1136/practneurol-2015-001162 Robiquet was one of the first to isolate and describe the properties of pure caffeine, [262] whereas Pelletier was the first to perform an elemental analysis. [263] a b c Juliano LM, Griffiths RR (October 2004). "A critical review of caffeine withdrawal: empirical validation of symptoms and signs, incidence, severity, and associated features". Psychopharmacology. 176 (1): 1–29. doi: 10.1007/s00213-004-2000-x. PMID 15448977. S2CID 5572188. Results: Of 49 symptom categories identified, the following 10 fulfilled validity criteria: headache, fatigue, decreased energy/ activeness, decreased alertness, drowsiness, decreased contentedness, depressed mood, difficulty concentrating, irritability, and foggy/not clearheaded. In addition, flu-like symptoms, nausea/vomiting, and muscle pain/stiffness were judged likely to represent valid symptom categories. In experimental studies, the incidence of headache was 50% and the incidence of clinically significant distress or functional impairment was 13%. Typically, onset of symptoms occurred 12–24 h after abstinence, with peak intensity at 20–51 h, and for a duration of 2–9 days.

Key facts

The biosynthesis of caffeine is an example of convergent evolution among different species. [202] [203] [204] In addition, there have been several reports of rhabdomyolysis related to excessive caffeine intake, although this is relatively rare ( 26, 27, 28, 29). Some analog substances have been created which mimic caffeine's properties with either function or structure or both. Of the latter group are the xanthines DMPX [210] and 8-chlorotheophylline, which is an ingredient in dramamine. Members of a class of nitrogen substituted xanthines are often proposed as potential alternatives to caffeine. [211] [ unreliable source?] Many other xanthine analogues constituting the adenosine receptor antagonist class have also been elucidated. [212] Caffeine is used as a primary treatment for apnea of prematurity, [40] but not prevention. [41] [42] It is also used for orthostatic hypotension treatment. [43] [42] [44] Myers RL (2007). The 100 Most Important Chemical Compounds: A Reference Guide. Greenwood Press. p. 55. ISBN 978-0-313-33758-1 . Retrieved 17 June 2018.