Due to its pleasant taste and supposed health benefits, tea is one of the most popular beverages. Tea drinking has been linked to health advantages since its inception, but scientific research on the beverage and its constituents has only been underway for around 30 years. Tea use, particularly green tea (GT), has been linked to a lower prevalence of chronic diseases in which oxidative stress has been implicated, such as cancer (Chung et al. 2003; Butt and Sultan 2009) and cardiovascular disease (Butt and Sultan 2009). (CVDs; Stangl et al. 2007; Babu and Liu 2008).

The high content of bioactive compounds like polyphenols may be linked to the health advantages attributed to tea intake. Polyphenols have been shown to have antioxidant, antiviral, and anti-inflammatory properties, as well as the ability to influence detoxification enzymes, increase immunological function, and reduce platelet aggregation (Lampe 2003; Frankel and Finley 2008). Epigallocatechin gallate (EGCG), one of the tea polyphenols, has been revealed to be responsible for much of green tea’s health-promoting properties (Khan et al. 2006). Because of the increased level of EGCG in GT, it has been proven to be superior to black tea (BT) in terms of health benefits, while the role of thearubigins and theaflavins in BT has not been thoroughly examined. In vitro and animal studies show that polyphenols produced from tea have bioactivity to delay the emergence of disease risk factors (Cabrera, Artacho, and Giménez 2006; Wolfram 2007; Yang et al. 2007; Yang et al. 2009; Yang, Lambert, and Sang 2009; Yang, Lambert, and Sang 2009).

Chemical components of tea & their health benefits

Tea contains the following phytoconstituents:

1. Tannins/Catechins

Catechins are a type of polyphenol that is the predominant astringency component in green tea and have been referred to as tannins for a long time. Catechin was first isolated from the Indian plant extract catechu (from the plant acacia catechu, a Fabaceae species in the acacia genus), from whence it gets its name. Dr. Michiyo Tsujimura of RIKEN (The Institute of Physical and Chemical Research) in Japan was the first to isolate tea catechin in 1929. Catechins are found in tea leaves in four different forms:

 Epicatechin

 Epigallocatechin

 Epicatechin gallate

 Epigallocatechin gallate

Some catechins change form throughout the production process for tea beverages due to heat processing. This change of form is mentioned as follows:

I. Epicatechin gets converted to Catechin

II. Epigallocatechin gets converted to Gallocatechin

III. Epicatechin gallate gets converted to Catechin gallate

IV. Epigallocatechin gallate gets converted to Gallocatechin gallate

Catechins are particularly prone to oxidation. Most catechins in green tea stay unoxidized because the process of creating crude tea entails preventing the action of oxidizing enzymes. The action of oxidizing enzymes produces oxidized polymers in oolong and black teas (complex catechins, such as theaflavins and thearubigins). In contrast to catechins, which are colorless in water, these oxidized catechins turn orange or red. The unique reddish color of oolong and black teas is due to this.

Young shoots (first or second leaf) have a higher catechin concentration than mature leaves (third or fourth leaf). The production of catechins is reduced in teas produced with cover culture to block out most light, such as Gyokuro, giving these teas a lower-catechin concentration than Sencha (approximately 10 percent as polyphenols).

Tea bushes create theanine in their roots, which then migrate to the leaves. When theanine is exposed to light, it is broken down into ethylamino, which is then converted into catechin. Teas high in theanine and low in catechin can be made using covered culture because theanine does not break down when not exposed to light.

Tea Catechins help decrease blood cholesterol and body fat. They have proven anti-cancer and anti-oxidant properties along with an anti-hyperglycemic effect. Tea catechins prevent tooth decay and have an anti-influenza effect.

2. Theanine (Amino Acid)

Tea is distinguished by its full-bodied, rich flavor (Umami), and sweetness. At the same time, it provides a calming effect. Theanine, a type of amino acid, is mostly responsible for these features.

Tea contains amino acids, which give it a full-bodied flavor and sweetness. More than 60% of these amino acids are theanine, a tea-specific amino acid. The structure of theanine is similar to that of glutamine, but it has a refined, rich flavor and sweetness. Other amino acids found in tea leaves include glutamine, asparagine, arginine, and serine, in addition to theanine.

Theanine is found in the tea plant (Camellia sinensis), as well as other camellia and sasanqua, but not in any other plants. Ichibancha has a higher theanine content than Nibancha, and even within Ichibancha, younger shoots have a higher theanine content. The amount of theanine in mature leaves decreases substantially. The production of catechins from amino acids is repressed when tea is cultivated utilizing cover culture (shaded from sunlight), as is the case with Gyokuro, resulting in a high theanine content in the tea leaves. Shincha and Gyokuro, on the other hand, have a rich, full-bodied flavor (Umami), whilst Bancha has a much lighter flavor.

Caffeine’s stimulating impact is reduced by theanine. A potentially powerful stimulant impact is instead turned into a modest effect thanks to its characteristics. This might be considered one of tea’s best natural qualities.

Theanine has been proven in animal studies to have capabilities for lowering blood pressure and protecting central nervous system cells. According to the ITO EN Central Research Institute, measurements of the brain waves of people who have eaten theanine reveal a rise in -waves, which are produced notably when a person is in a calm state.

3. Caffeine

Tea can help a person feel rejuvenated after a long day at work or school. Caffeine, which is contained in tea, has this effect. Although there isn’t much of a difference in caffeine concentration depending on when the tea is selected, such as between Ichibancha and Nibancha, there is a larger caffeine content in young shoots and mature leaves, similar to catechin and amino acid (theanine). Caffeine is sublimated (converted straight from a solid to a gaseous form) and is claimed to diminish in teas that have been roasted at high temperatures, such as Hojicha.

4. Vitamins

Green tea is noted for having higher concentrations of vitamins than other foods, which makes it a superior beverage. Vitamin C and other vitamins are generally lost during the processing process of several types of oolong and black teas.

Vitamin C

Sencha has the highest content of Vitamin C of any tea, around 1.5 times that of red peppers, which has one of the highest concentrations of Vitamin C among vegetables. Oolong tea, on the other hand, has very little Vitamin C and black tea has none at all.


Green tea (Matcha and Sencha) provides about the same amount of folic acid as spinach or parsley, and around the same amount as dried seaweed, which has one of the highest quantities of any food. Only a minor amount of folic acid is found in black tea.

Vitamin E

Sencha has 32 times the amount of Vitamin E found in spinach and two times the amount found in chili peppers, and few foods have a higher concentration. Vitamin E, on the other hand, does not dissolve in water and is best consumed in the form of powdered green tea or Matcha.

Riboflavin (Vitamin B2)

Sencha contains more than 4 times the amount of Vitamin B2 found in parsley, spinach, and Jew’s marrow, which have some of the highest quantities among foods.


Matcha includes five times the amount of -carotene found in carrots, making it an exceptionally high-carotene food.

5. Saponins

Saponins are found in all teas and are responsible for the foaming seen in Matcha tea. Tea leaves contain about 0.1 percent saponins, which are responsible for the tea’s bitterness and astringency. Saponins have been proven to decrease blood pressure, prevent obesity, and influenza, and have antifungal, anti-inflammatory, and anti-allergy activities.

6. Fluorine

The plant Camellia japonica contains a lot of fluorine, and mature leaves have more fluorine than younger ones, with Bancha having the most fluorine of all the teas. It helps to prevent cavities by forming an acid-resistant outer layer on the teeth’ surface.

7. γ-Aminobutyric Acid (GABA)

When raw leaves are left without oxygen, GABA is generated. Gabalong tea is made by processing them into dry tea leaves. GABA includes components that have been shown to lower blood pressure in animal studies with Gabalong tea. GABA lowers blood pressure.

8. Minerals

Tea contains 5-7 percent minerals, including potassium (K), calcium (Ca), phosphorus (P), and magnesium (Mg), with minor amounts of manganese (Mn), zinc (Zn), and copper (Cu) (Cu).

Classification of tea

Tea is classified into many categories depending on how it is prepared. There are at least six different types:

1. White:

Unoxidized and withered

2. Yellow:

Neither wilted nor rusted, but allowed to turn yellow

3. Green:

Indicates that the plant is unwilted and unoxidized.

4. Oolong tea:

Wilted, damaged, and slightly oxidized

5. Black:

Wilted, occasionally crushed, and highly oxidized (in Chinese and other East Asian tea cultures, this is called [hóngchá], “red tea”).

6. Post-fermented:

Green tea that has been left to ferment/compost (referred to as Pu’er in the Yunnan district of South-Western China or [hichá] “black tea” in Chinese tea culture).

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