Schmidt B, Anderson PJ, Doyle LW, Dewey D, Grunau RE, Asztalos EV, Davis PG, Tin W, Moddemann D, Solimano A, Ohlsson A, Barrington KJ, Roberts RS (January 2012). "Survival without disability to age 5 years after neonatal caffeine therapy for apnea of prematurity". JAMA. 307 (3): 275–82. doi: 10.1001/jama.2011.2024. PMID 22253394.

Robertson D, Wade D, Workman R, Woosley RL, Oates JA (April 1981). "Tolerance to the humoral and hemodynamic effects of caffeine in man". The Journal of Clinical Investigation. 67 (4): 1111–7. doi: 10.1172/JCI110124. PMC 370671. PMID 7009653. Caffeine can also interact with other stimulants such as cocaine and methamphetamine. It can increase your risk of problems such as an abnormal health rate or heart rhythm. How can I reduce my caffeine intake?For instance, the amount found in one cup of coffee can take as little as 20 minutes to reach the bloodstream and about 1 hour to reach full effectiveness ( 1). Summary Consumption of caffeine after abdominal surgery shortens the time to recovery of normal bowel function and shortens length of hospital stay. [48] For most of us, to be caffeinated to one degree or another has simply become baseline human consciousness. Something like 90% of humans ingest caffeine regularly, making it the most widely used psychoactive drug in the world, and the only one we routinely give to children (commonly in the form of fizzy drinks). Few of us even think of it as a drug, much less our daily use of it as an addiction. It’s so pervasive that it’s easy to overlook the fact that to be caffeinated is not baseline consciousness but, in fact, an altered state. It just happens to be a state that virtually all of us share, rendering it invisible.

People with existing medical conditions, such as high blood pressure, may be more sensitive to caffeine. This can make a normal amount of caffeine more dangerous. If you have an existing medical condition, it’s a good idea to eat or drink less caffeine. The scientists have spelled out, and I had duly noted, the predictable symptoms of caffeine withdrawal: headache, fatigue, lethargy, difficulty concentrating, decreased motivation, irritability, intense distress, loss of confidence and dysphoria. But beneath that deceptively mild rubric of “difficulty concentrating” hides nothing short of an existential threat to the work of the writer. How can you possibly expect to write anything when you can’t concentrate? USDA Food Data Central. U.S. Department of Agriculture, Agricultural Research Service. https://fdc.nal.usda.gov/index.html. Accessed April 18, 2022. In 1629 the first coffeehouses in Europe, styled on Arab and Turkish models, popped up in Venice, and the first such establishment in England was opened in Oxford in 1650 by a Jewish immigrant. They arrived in London shortly thereafter, and proliferated: within a few decades there were thousands of coffeehouses in London; at their peak, one for every 200 Londoners. Decaffeinated" coffees do in fact contain caffeine in many cases– some commercially available decaffeinated coffee products contain considerable levels. One study found that decaffeinated coffee contained 10mg of caffeine per cup, compared to approximately 85mg of caffeine per cup for regular coffee. [208] Detection in body fluidsI thought of myself as a pretty good sleeper before I met Walker. At lunch he probed me about my sleep habits. I told him I usually get a solid seven hours, fall asleep easily, dream most nights. For the general population of healthy adults, Health Canada advises a daily intake of no more than 400mg. [72] This limit was found to be safe by a 2017 systematic review on caffeine toxicology. [73] Children The leaves of Ilex vomitoria, the yaupon holly tree, are placed in boiling water to make a yaupon tea. Caffeine does not affect the way your body absorbs alcohol. It will not reduce your blood alcohol concentration or help you 'sober up' after a big night. 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.