Some textbooks state that caffeine is a mild euphoriant, [104] [105] [106] while others state that it is not a euphoriant. [107] [108]

Gibbons CH, Schmidt P, Biaggioni I, Frazier-Mills C, Freeman R, Isaacson S, Karabin B, Kuritzky L, Lew M, Low P, Mehdirad A, Raj SR, Vernino S, Kaufmann H (August 2017). "The recommendations of a consensus panel for the screening, diagnosis, and treatment of neurogenic orthostatic hypotension and associated supine hypertension". J. Neurol. 264 (8): 1567–1582. doi: 10.1007/s00415-016-8375-x. PMC 5533816. PMID 28050656. We do know that many regular coffee drinkers become dependent on caffeine. Regular heavy use of caffeine, more than 600mg a day, can cause: Some beverages combine alcohol with caffeine to create a caffeinated alcoholic drink. The stimulant effects of caffeine may mask the depressant effects of alcohol, potentially reducing the user's awareness of their level of intoxication. Such beverages have been the subject of bans due to safety concerns. In particular, the United States Food and Drug Administration has classified caffeine added to malt liquor beverages as an "unsafe food additive". [246] In general, dark-roast coffee has very slightly less caffeine than lighter roasts because the roasting process reduces caffeine content of the bean by a small amount. [229] [230] Tea Cano-Marquina A, Tarín JJ, Cano A (May 2013). "The impact of coffee on health". Maturitas. 75 (1): 7–21. doi: 10.1016/j.maturitas.2013.02.002. PMID 23465359.

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Children under 18 years should consume less than 3mg for each kilo of body weight a day. For a 40kg child, this is about 120mg a day, or 2 cans of cola (375mL). There is evidence that amounts greater than this can cause increased anxiety. 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 Gut health. Consuming 3 cups of coffee a day for as few as 3 weeks may increase the amount and activity of beneficial gut bacteria ( 52).

Conger SA, Warren GL, Hardy MA, Millard-Stafford ML (February 2011). "Does caffeine added to carbohydrate provide additional ergogenic benefit for endurance?" (PDF). International Journal of Sport Nutrition and Exercise Metabolism. 21 (1): 71–84. doi: 10.1123/ijsnem.21.1.71. PMID 21411838. S2CID 7109086. Archived from the original (PDF) on 14 November 2020.Alpecin shampoo is one of the most well-known on the market specializing in caffeine-based hair care products. Caffeine's biological half-life– the time required for the body to eliminate one-half of a dose– varies widely among individuals according to factors such as pregnancy, other drugs, liver enzyme function level (needed for caffeine metabolism) and age. In healthy adults, caffeine's half-life is between 3 and 7hours. [8] The half-life is decreased by 30-50% in adult male smokers, approximately doubled in women taking oral contraceptives, and prolonged in the last trimester of pregnancy. [126] In newborns the half-life can be 80hours or more, dropping very rapidly with age, possibly to less than the adult value by age 6 months. [126] The antidepressant fluvoxamine (Luvox) reduces the clearance of caffeine by more than 90%, and increases its elimination half-life more than tenfold; from 4.9hours to 56hours. [187] a b c d "Caffeine in Food". Health Canada. 6 February 2012. Archived from the original on 10 August 2020 . Retrieved 24 August 2020. Yang TW, Wang CC, Sung WW, Ting WC, Lin CC, Tsai MC (March 2022). "The effect of coffee/caffeine on postoperative ileus following elective colorectal surgery: a meta-analysis of randomized controlled trials". International Journal of Colorectal Disease. 37 (3): 623–630. doi: 10.1007/s00384-021-04086-3. PMC 8885519. PMID 34993568. S2CID 245773922.

One thing to keep in mind is that caffeine may slightly raise blood pressure in some people. However, this effect is generally small (3–4 mmHg) and tends to fade for most individuals when they consume coffee regularly ( 32, 33, 34, 35).Gaudiya Vaishnavas generally also abstain from caffeine, because they believe it clouds the mind and overstimulates the senses. [284] To be initiated under a guru, one must have had no caffeine, alcohol, nicotine or other drugs, for at least a year. [285] A systematic review and meta-analysis from 2014 found that concurrent caffeine and L-theanine use has synergistic psychoactive effects that promote alertness, attention, and task switching; [57] these effects are most pronounced during the first hour post-dose. [57] Physical performance It contains a special purple pigment that helps prevent the discoloration or yellowing of hair. Using the shampoo daily can create a slight purple hue on hair – only use it every fourth wash.

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. One review reports that after participants ingested 37.5–450 mg of caffeine, they had improved alertness, short-term recall, and reaction time ( 1). Funk GD (November 2009). "Losing sleep over the caffeination of prematurity". The Journal of Physiology. 587 (Pt 22): 5299–300. doi: 10.1113/jphysiol.2009.182303. PMC 2793860. PMID 19915211. Liver protection. Coffee may reduce the risk of liver damage (cirrhosis) by as much as 84%. It may slow disease progression, improve treatment response, and lower the risk of premature death ( 37, 38). A study found that a second cup of coffee produced no further benefits unless it was consumed at least 8 hours after the first cup ( 9).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] Caffeine may be synthesized in the lab starting with dimethylurea and malonic acid. [ clarification needed] [200] [201] [205] Alpecin Double-Effect Caffeine Shampoo was developed for oily dandruff. These somewhat larger, plaque-like dandruff flakes are the result of a greasy scalp. In the first step, Alpecin Double-Effect Caffeine Shampoo loosens the crusted cells of the horny layer and thoroughly frees the scalp of dandruff. The effective anti-dandruff agents salicylic acid and piroctone olamine prevent the formation of new dandruff. In the second step, the caffeine complex recharges the hair with energy. Liddle DG, Connor DJ (June 2013). "Nutritional supplements and ergogenic AIDS". Primary Care. 40 (2): 487–505. doi: 10.1016/j.pop.2013.02.009. PMID 23668655. Amphetamines and caffeine are stimulants that increase alertness, improve focus, decrease reaction time, and delay fatigue, allowing for an increased intensity and duration of training... It’s important to note that coffee and tea contain other bioactive compounds (besides caffeine) that may also be beneficial. Summary