Tea (Camellia sinensis)

Last Updated: September 28, 2022

Tea is both the common name of Camellia sinensis and the name of an infusion made with the leaves of this plant. Green tea is unfermented; black tea is fermented; oolong tea is partially fermented.

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Contents of Camellia Sinensis

Plants derived from Camellia Sinensis (Green, Black, White, and Oolong Tea) contain:


Processing of types of Camellia Sinensis


White Tea

White tea is unique in the fact that it is processed from unopened buds, classified as silver needles (bai hao Yinzhen), or an unopened bud with two leaves covered in white leaf hairs.[10] Afterwards, they are sometimes dried or withered by the air to remove moisture content; this leaves them with a curled silvery appearance.

It tends to be known as the most relaxing tea of the list, as it has highest levels of GABA,[11] Pu-erh tea has the lowest as GABA is lost during fermentation.


Oolong Tea

Oolong tea tends to, like white tea, be partially oxidized.

As they still have active enzymes, some of the catechin content is polymerized into theaflavins and thearubigins.


Green Tea

Green Tea leaves tend to be non-oxidized.


Black Tea

Black tea leaves tend to be fully oxidized.


Pu-erh (Fermented) Tea: Dark Tea

After initial picking, Pu-erh tea leaves are turned into raw Pu-erh by a process called 'kill green' and then fermented by microorganisms for 6-12 months.[2] Some of the more high quality Pu-erh teas are fermented for greater than a decade.[12]

Pu-erh tea has a taste that is described as 'complex, silky smooth, and mellow' but develops a sensory experience similar to green tea after being aged, but perhaps slightly more bitter.[2]

When tea is fermented by bacteria, levels of catechins initially drop.[2] However, new compounds are generated via microorganisms, such as theabrownin[13] and statins, which is produced by the Streptomyces cinereus strain Y11 bacteria.[12][14]

Overall, green tea is the 'basic' tea that is enzymatically inactive and non-oxidized. White tea and Oolong tea are partially oxidized, but Oolong is still enzymatically active. Black tea is fully oxidized and enzymatically active. Pu-erh tea is fermented and quite unique from the other teas.


Preparation of Tea for Home Consumption

In studies looking at the interactions between milk and tea catechins (ie. adding milk to your tea) the milk can form protein-catechin complexes with the tea catechins which negate the anti-oxidant potential (by sequestering hydroxyl groups).[15] This, however, is not likely to result in a reduced bioavailability.[16] Although the protein-catechin complex is metabolically inactive, it is digested and free catechins are released in the intestines.[16] Bioavailability studies looking at all tea catechins note no differences in overall serum levels of free catechins (green and black tea) when milk is added at a 1:5 ratio of milk:tea,[17] although a partitioning effect has been observed, with less EGCG and ECG being absorbed yet more EC and EGC.[18]

One study noted that milk ingestion with green tea abolished the catechins' beneficial effects on cardiovascular health (vasorelaxation),[19] but has been criticized for its methodology as it took a single measurement 2 hours after ingestion when the benefits associated with green tea could be chronic in nature.

Consumption of tea with milk may alter but does not significantly reduce the bioavailability of green tea catechins; it has been suggested that proteins may abolish the benefits of green tea catechins on heart health, but the lone study supporting this notion has some methodological flaws


Comparison of Tea types

Green Tea Catechin content varies depending on species:

  • White tea tends to be in the range of 14.40 to 369.60 mg/g of dry plant material[20]
  • Green tea tends to be in the range of 21.38 to 228.20 mg/g of dry plant material[20]

In comparing different sources of Camellia Sinensis:

  • White tea appears to have more catechins overall by weight, but when the catechin content is even green tea has a higher anti-oxidant potential[20]
  • When fermented, tea tends to lose antioxidative potential; however, some measures of anti-inflammatory status increase (as measured by macrophage NO release via LPS)[21]
  • Green tea appears to be the least effective at inhibiting the ACE enzyme in blood pressure regulation, with green < oolong < white < black < dark teas.[22]
7.^Ali M, Afzal M, Gubler CJ, Burka JFA potent thromboxane formation inhibitor in green tea leavesProstaglandins Leukot Essent Fatty Acids.(1990 Aug)
8.^Afzal M, Al-Sweedan N, Massih LA, Takahashi K, Shibata S2-Amino-5-(N-ethylcarboxamido)-pentanoic Acid from Green Tea LeavesPlanta Med.(1987 Feb)
11.^Zhao M, Ma Y, Wei ZZ, Yuan WX, Li YL, Zhang CH, Xue XT, Zhou HJDetermination and comparison of γ-aminobutyric acid (GABA) content in pu-erh and other types of Chinese teaJ Agric Food Chem.(2011 Apr 27)
12.^Jeng KC, Chen CS, Fang YP, Hou RC, Chen YSEffect of microbial fermentation on content of statin, GABA, and polyphenols in Pu-Erh teaJ Agric Food Chem.(2007 Oct 17)
15.^Arts MJ, Haenen GR, Wilms LC, Beetstra SA, Heijnen CG, Voss HP, Bast AInteractions between flavonoids and proteins: effect on the total antioxidant capacityJ Agric Food Chem.(2002 Feb 27)
16.^van der Burg-Koorevaar MC, Miret S, Duchateau GSEffect of milk and brewing method on black tea catechin bioaccessibilityJ Agric Food Chem.(2011 Jul 27)
17.^van het Hof KH, Kivits GA, Weststrate JA, Tijburg LBBioavailability of catechins from tea: the effect of milkEur J Clin Nutr.(1998 May)
18.^Egert S, Tereszczuk J, Wein S, Müller MJ, Frank J, Rimbach G, Wolffram SSimultaneous ingestion of dietary proteins reduces the bioavailability of galloylated catechins from green tea in humansEur J Nutr.(2012 Feb 25)
19.^Lorenz M, Jochmann N, von Krosigk A, Martus P, Baumann G, Stangl K, Stangl VAddition of milk prevents vascular protective effects of teaEur Heart J.(2007 Jan)
20.^Unachukwu UJ, Ahmed S, Kavalier A, Lyles JT, Kennelly EJWhite and green teas (Camellia sinensis var. sinensis): variation in phenolic, methylxanthine, and antioxidant profilesJ Food Sci.(2010 Aug 1)
21.^Xu Y, Zhao H, Zhang M, Li CJ, Lin XZ, Sheng J, Shi WVariations of Antioxidant Properties and NO Scavenging Abilities during Fermentation of TeaInt J Mol Sci.(2011)