Editing Tea (section)

== Chemical composition ==
{{See also|Phenolic content in tea}}

Physically speaking, tea has properties of both a [[solution (chemistry)|solution]] and a [[suspension (chemistry)|suspension]]. It is a solution of the water-soluble compounds extracted from the tea leaves, such as the polyphenols and amino acids. Tea infusions are among most consumed beverages globally.<ref>{{Cite journal|last1=Yang|first1=Ziyin|last2=Baldermann|first2=Susanne|last3=Watanabe|first3=Naoharu|date=1 October 2013|title=Recent studies of the volatile compounds in tea|url=https://www.sciencedirect.com/science/article/pii/S096399691300104X|journal=Food Research International |series=Tea – from bushes to mugs: composition, stability and health aspects |volume=53 |issue=2 |pages=585–599 |doi=10.1016/j.foodres.2013.02.011 |issn=0963-9969}}</ref>

[[Caffeine]] makes up about 3% of tea's dry weight, which translates to between 30 and 90 milligrams per {{convert|250|mL|usfloz|adj=on|frac=2}} cup depending on the type, brand,<ref>{{cite book |author1=Weinberg, Bennett Alan |author2=Bealer, Bonnie K. |name-list-style=amp |title=The World of Caffeine: The Science and Culture of the World's Most Popular Drug |url=https://archive.org/details/worldofcaffeines00benn |url-access=registration  |publisher=Routledge |year=2001 |isbn=978-0-415-92722-2 |page=[https://archive.org/details/worldofcaffeines00benn/page/228 228]}}</ref> and brewing method.<ref>{{cite journal |vauthors=Hicks MB, Hsieh YP, Bell LN |title=Tea preparation and its influence on methylxanthine concentration |journal=Food Research International |volume=29 |issue=3–4 |pages=325–330 |year=1996 |doi=10.1016/0963-9969(96)00038-5 |url=http://www2.hcmuaf.edu.vn/data/lhquang/file/Tea1/Tea%20preparation%20and%20its%20influence%20on%20methylxanthine.pdf |access-date=13 May 2013 |archive-url=https://web.archive.org/web/20130203132842/http://www2.hcmuaf.edu.vn/data/lhquang/file/Tea1/Tea%20preparation%20and%20its%20influence%20on%20methylxanthine.pdf |archive-date=3 February 2013 |url-status=live}}</ref> A study found that the caffeine content of one gram of black tea ranged from 22 to 28&nbsp;mg, while the caffeine content of one gram of green tea ranged from 11 to 20&nbsp;mg, reflecting a significant difference.<ref>{{cite journal |pmc=3459493 |pmid=23055579 |doi=10.4103/0972-124X.99256 |volume=16 |issue=2 |title=Green tea: A boon for periodontal and general health |year=2012 |journal=Journal of Indian Society of Periodontology |pages=161–167 |vauthors=Chatterjee A, Saluja M, Agarwal G, Alam M |doi-access=free }}</ref> Tea contains small amounts of [[theobromine]] and [[theophylline]], which are [[xanthine]]s and [[stimulant]]s, similar to caffeine.<ref>{{cite journal |pmid=1614995 |year=1992 |last1=Graham |first1=HN |title=Green tea composition, consumption, and polyphenol chemistry |volume=21 |issue=3 |pages=334–350 |journal=Preventive Medicine |doi=10.1016/0091-7435(92)90041-f}}</ref>

[[File:TeaLeaves.JPG|thumb|Fresh tea leaves in various stages of growth]]

The [[Astringent|astringency]] in tea can be attributed to the presence of [[polyphenol]]s. These are the most abundant compounds in tea leaves, making up 30–40% of their composition.<ref>{{cite journal |last=Harbowy |first=ME |year=1997 |title=Tea Chemistry |journal=Critical Reviews in Plant Sciences |volume=16 |issue=5 |pages=415–480 |doi=10.1080/713608154}}</ref> Polyphenols in tea include [[flavonoid]]s, [[epigallocatechin gallate]] (EGCG), and other [[Flavan-3-ol|catechins]].<ref>{{cite journal |last1=Ferruzzi |first1=MG |year=2010 |title=The influence of beverage composition on delivery of phenolic compounds from coffee and tea |journal=Physiol Behav |volume=100 |issue=1 |pages=33–41 |doi=10.1016/j.physbeh.2010.01.035 |pmid=20138903|s2cid=207373774 }}</ref><ref>{{cite journal |vauthors=Williamson G, Dionisi F, Renouf M |year=2011 |title=Flavanols from green tea and phenolic acids from coffee: critical quantitative evaluation of the pharmacokinetic data in humans after consumption of single doses of beverages |journal=Mol Nutr Food Res |volume=55 |issue=6 |pages=864–873 |pmid=21538847 |doi=10.1002/mnfr.201000631}}</ref> Although there has been preliminary [[clinical research]] on whether green or black teas may protect against various human diseases, there is no evidence that tea polyphenols have any effect on health or lowering disease risk.<ref name="nccih">{{cite web |url=http://nccih.nih.gov/health/greentea |publisher=National Center for Complementary and Integrative Health, US National Institutes of Health, Bethesda, MD |title=Green Tea |date=2014 |access-date=25 October 2014 |archive-url=https://web.archive.org/web/20150402153347/https://nccih.nih.gov/health/greentea |archive-date=2 April 2015 |url-status=live}}</ref><ref>{{cite web |url=https://www.fda.gov/Food/IngredientsPackagingLabeling/LabelingNutrition/ucm073992.htm#gtea |title=Summary of Qualified Health Claims Subject to Enforcement Discretion:Green Tea and Cancer |publisher=Food and Drug Administration, US Department of Health and Human Services |date=October 2014 |access-date=25 October 2014 |archive-url=https://web.archive.org/web/20141015104050/http://www.fda.gov/Food/IngredientsPackagingLabeling/LabelingNutrition/ucm073992.htm#gtea |archive-date=15 October 2014 |url-status=live}}</ref>