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Journal of Multidisciplinary Applied Natural Science Vol. 2 No. 2 (2022) https://doi.org/10.47352/jmans.2774-3047.117

Review Article

Therapeutic Properties of Green Tea: A Review

Sonia Ratnani and Sarika Malik*
Received : February 09, 2022 Revised : March 31, 2022 Accepted : April 04, 2022 Online : April 05, 2022

Abstract
The most consumed beverage in the world is tea after water. Till today the consumption of black tea is 70% while that of green tea
is only 20%. One reason for this percentage is lack of awareness about green tea and invested research. Green tea along with
caffeine which imparts characteristic taste, bitterness and stimulating effect, is also rich in a group of chemicals, called catechin
polyphenols (commonly known as tannins, which contribute to bitter taste and astringency) and deliver antioxidant properties.
Furthermore, green tea also comprises of amino acids such as theanine along with alkaloids such as adenine, dimethylxanthine,
theobromine, theophylline and xanthine. Some vitamins, like vitamin A, vitamin B1, vitamin B2, vitamin B3, vitamin
C, and vitamin E are also found in green tea. The present review gives the study of various constituents of green tea and their
impact on human health. Studies provide strong evidence that owing to antioxidant properties daily intake of green tea may be used
as a preventive measure for different types of cancer and other diseases. This review gives a detailed analysis of constituents of
green tea and highlighting it's potential as a natural nutraceutical. However, although much of the documented literature mentions
positive effect yet much had to be explored on correlation between concentration of green tea and toxicity.

Keywords green tea, polyphenols, human health, antioxidant

1. INTRODUCTION type of cancer. These benefits have resulted in

discussion which focus on the dietary guidance and
Our health is wrapped in our lifestyle and genes recommended drinking for green tea [10]. Through
today, thus, no food can protect us from diseases available research it is an attempt to depict the
except our care and attention. Nowadays tea is health benefits of green tea. The aim of this review
considered to be second most consumed beverage is to provide information and evidence pertaining to
in the world [1]. During last few years green tea has health benefits obtained from consumption of green
gained lot of importance as a beverage owing to its tea with special reference to cancer diseases.
health benefits. Recent studies have shown that
green tea helps in improving blood vessels hence 2. GREEN TEA: HISTORICAL
lower the cholesterol and reduce the risk of cardio PERSPECTIVE
vascular diseases [2]–[5]. MRI’s reveal that
drinking green tea have greater activity and can Green Tea is one of the healthiest beverages
enhance our brain's cognitive functions, particularly originated from China more than 4000 years ago
the working memory [6]. Green tea helps in and has been used in traditional Chinese medicine
controlling the levels of blood sugar in people for a wide variety of health benefits [11]. It comes
suffering from diabetes [7]. It blocks the formation from the steamed and dried leaves of the Camella
of plaque related to Alzheimer diseases [8][9]. It is sinesis plant. The plant originates from China and
found as fat burning supplement as it increases fat also produces black tea, oolong tea and several
burning and boost the metabolic rate in human other varieties of tea through different processing
controlled trial. Most important due to presence of methods. Green tea is made by harvesting the plant
antioxidants it helps in lowering the risks of various leaves, withering them and then steaming them.
Copyright Holder: Steaming halts, the process of enzymatic oxidation–
© Ratnani, S. and Malik, S. (2022) which causes the darkening of the tea leaves – and
allowed the leaves to remain closer to their natural
First Publication Right:
Journal of Multidisciplinary Applied Natural Science
“green” state. This indicates that it goes through
minimal oxidation during processing which possess
Publisher’s Note: powerful oxidants. The real history of green tea
Pandawa Institute stays neutral with regard to jurisdictional dates back to the 8th century, when the method of
claims in published maps and institutional affiliations.
steaming the leaves to inhibit their oxidation was
This Article is Licensed Under: discovered. In the 12th century a new frying
method of “fixing” the leaves was introduced. Both

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proanthocyanidins, and caffeine (~3%). Among the
different polyphenols, catechins and flavonols
(myricetin, caempherol, quercetin, chlorogenic acid,
coumarylquinic acid, and theogallin) form the
major constituents (Figure 2) [14].

3.1 Polyphenols (Catechins and Flavanols)

About 30% of the leaves by weight are flavanols
which comprise mainly of catechins (derives its
name from Indian plant Acacia catechu (a tree of
Figure 1. Green tea plant. Fabaceae family, Acaria genes) from which it is
of these processes resulted in teas that have the isolated). Green tea comprises of catechin (C),
characteristic un-oxidized taste and appearance to epicatechin (EC), gallocatechin (GC),
modern green teas, and both processes are still in epigallocatechin (EGC), epicatechin gallate (ECG),
use today. Since those early days, as the popularity epigallocatechin gallate (EGCG), and gallocatechin
and production of green tea increased the methods gallate (GCG) as the major catechins [15][16].
of producing green tea have continuously evolved Green tea hence is considered to be principal source
and improved. of catechins among various dietary sources [17].
These are mainly responsible for the astringency
2.1 Plant Description component in green tea. Among all catechins the
Green, black, and oolong tea are all derived four primary catechins EC, EGCG, ECG, and EGC
from the leaves of the C. sinensis plant. Originally form 80% of the total catechins (Figure 3) [18]. All
cultivated in East Asia, this plant grows as large as these catechins similar properties while EGCG
a shrub or tree (Figure 1) [12][13]. Today, C. appears to be most potent catechin and accounts for
sinensis grows throughout Asia and parts of the 50—80% of the total catechins followed by EGC (9
Middle East and Africa. –12%), ECG (9–12%) and EC (5–7%) [19].
People in Asian countries more commonly Chemically catechins are polyphenolic
consume green and oolong tea while black tea is the compounds with diphenyl propane skeleton. The
most popular drink in the United States. Green tea chemical structure consists of a polyphenolic ring
is prepared from unfermented leaves, the leaves of condensed with six-membered oxygen containing
oolong tea are partially fermented, and black tea is heterocyclic ring that carries another polyphenolic
fully fermented. The more the leaves are fermented, ring at the 2 position. Catechins are characterized
the lower the polyphenol content and the higher the by multiple of hydroxyl groups on the A and B
caffeine content. Green tea has the highest rings. EC is an epimer containing two hydroxyl
polyphenol content and 2-3 times less caffeine groups at 3′ and 4′ position of B ring and a hydroxyl
content then black tea. group at 3 position of the C ring [20]. The only
structural difference between EGC and EC is that
2.2 Doses EGC possesses an additional hydroxyl group at 5′
Pediatric, Green tea has not been studied in position of the B ring. ECG and EGCG are ester
children, so it is not recommended for pediatric use. derivatives of EC and EGC, respectively, through
Adult, depending on the brand, 2 to 3 cups of green esterification at 3 hydroxyl position of the C ring
tea per day (for a total of 240 to 320 mg with a gallate moiety (Figure 3) [21][22].
polyphenols) or 100 to 750 mg per day of According to the European Food Safety
standardized green tea extract is recommended. Authority (EFSA), 126 mg of catechins are present
in per 100 mL of green tea. Meanwhile, according
3. CHEMICAL COMPOSITION to the Food and Drug Administration (FDA), 71 mg
of epigallocatechin gallate will be present in per
Green tea mainly consists of mainly polyphenols 100 mL of green tea [23].
(~90%), amino acids (~7%), theanine,

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3.2 Alkaloids
Leaves of green tea primarily contain alkaloids
including caffeine, theobromine, and theophylline.
They provide green tea's stimulant effects. Amount
of caffeine (2—5%) in tea leaves depends on the
age of the leaf with younger leaves to have it in
high concentration [24].

3.3 Amino Acids

15—20% of dry weight of tea comprises of
proteins in enzymes that constitute an important
fraction of amino acids (1—4% dry weight) such as Figure 2. Chemical composition of green tea.
theanine or 5-N- ethylglutamine, glutamic acid, 3.6 Lipids
tryptophan, glycine, serine, aspartic acid, tyrosine, Small amounts of lipids such as linoleic and α-
valine, leucine, threonine, arginine, and lysine. L- linolenic acids also constitute green tea. The non-
theanine has been studied for its calming effects on drying oil content of green tea leaves is 4% by
the nervous system. weight with a solidifying temperature of around -5
to 15 °C [25].
3.4 Carbohydrates The composition of various constituents present
5-7% dry weight of green tea comprise of in green tea varies with genetic strain, climatic
carbohydrates which include cellulose, pectins, conditions, soil properties, plucking season,
glucose, fructose, and sucrose. position of leaf, processing and storage. Analysis
and evaluation of components of green tea is
3.5 Vitamins and Minerals needed to assess the potential benefits and risks
Vitamin content of green tea is higher than other associated with green tea. Researchers think the
drinks which thus make it superior. It comprises of health properties of green tea are mostly due to
important vitamins such as vitamin B2, vitamin C, polyphenols, chemicals with potent antioxidant
vitamin E and folic acid. Minerals are important as potential. In fact, the antioxidant effects of
they act as bodily regulators. The approximate polyphenols seem to be greater than vitamin C. The
composition of minerals in tea is 5—7% as polyphenols in green tea also give it a somewhat
elements such as potassium (K), calcium (Ca), bitter flavor.
phosphorus (P), and magnesium (Mg), as well as
small quantities of manganese (Mn), zinc (Zn) and 4. HEALTH BENEFITS OF GREEN TEA
copper (Cu).
Tea catechins have been largely studied for their

Figure 3. Different forms of Catechins.

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Figure 4. Health benefits of green tea.

antioxidant capacities and considered as important may help treat the following health conditions
antioxidants. The antioxidant effects of catechins (Figure 4).
are presumed to play a major role in mediating the
cardioprotective role of tea, although emerging 4.1 Cancer
evidence shows that catechins also have antioxidant Several population-based studies suggest that
-independent vascular effects, which will be both green and black teas help in protecting against
discussed elsewhere in this review. Green tea some cancers hence it has potent anticarcinogenic
catechins can exert both direct and indirect behavior [30]–[37]. For example, the cancer rates
antioxidant effects on cardiovascular system. tend to be low in countries such as Japan where
Catechins present antioxidant activity through people regularly consume green tea. However, it is
scavenging reactive oxygen species (ROS), not possible to be sure of these studies results
chelating redox active transition- metal ions, whether green tea actually prevents cancer in
inhibiting redox sensitive transcription factors, people. Early clinical studies suggest that the
inhibiting pro-oxidant enzymes and inducing polyphenols in tea, especially green tea, may play
antioxidant enzymes. Green tea intake lowers an important role in the prevention of cancer.
fasting serum total and LDL (low density lipid) Researchers also believe that polyphenols help
cholesterol in adults: a meta-analysis of 14 killing the various cancerous cells in human being.
randomized controlled trials.
In traditional Chinese and Indian medicine, 4.1.1 Bladder Cancer
practitioners used green tea as a stimulant, a Medical and healthcare system have defined
diuretic (to get rid of the body of excess fluid), an complementary and alternative medicine (CAM) as
astringent (to control bleeding and help heal an approach for patients suffering from bladder
wounds), and to improve heart health. Other cancer. One of these strategies mentions intake of
traditional techniques use of green tea include green tea and green tea polyphenols (GTP’s) [38].
treating gas, regulating body temperature and blood In one study that compared people with and without
sugar, promoting digestion, and improving mental bladder cancer, researchers found that women who
processes [26]–[29]. drank black tea and powdered green tea were less
Green tea has been extensively studied in likely to develop bladder cancer. A follow-up
people, animals, and laboratory experiments. clinical study by the same group of researchers
Results from these studies suggest that green tea revealed that people with bladder cancer,

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particularly men, who drank green tea had a better 5 China, researchers found that women who drank at
-year survival rate than those who did not drink least one cup of green tea per day lived longer with
green tea. People with cancer should consult with the disease than those who did not drink green tea.
their doctor before adding tea to their daily diet. In fact, those who drank the most tea, lived the
longest. However, other studies found no beneficial
4.1.2 Breast Cancer effects [39].
It has been observed in laboratory test tube and
animal studies that EGCG is responsible for 4.1.4 Colorectal Cancer
inhibiting the growth of breast cancer cells. There are conflicting results on the effect of
Numerous studies have investigated the therapeutic green tea on colorectal cancer. Some studies
effects of green tea on breast cancer using different indicate decreased risk on consumption of tea,
rodent models with a range of green tea products while others show increased risk. In one of the
including green tea mixtures as well [29]. In a study study, women who consumed more than five cups
of 472 women with various stages of breast cancer, of green tea per day faced a lower risk of compared
researchers found that women who drank more to non-green tea drinkers. However, studies in
green tea had the least cancer spread. It was women show that regular consumption may reduce
especially true in premenopausal women in the the risk of colorectal cancer [40].
early stages of breast cancer. They also found that
women with early stages of the disease who drank 4.1.5 Esophageal Cancer
at least 5 cups of tea daily before being diagnosed Studies in laboratory animals have found that
with cancer were less likely to experience a green tea polyphenols inhibit the growth of
recurrence after they finished treatment. However, esophageal cancer cells. However, studies in people
women with late stages of breast cancer had little or have produced conflicting findings. For example,
no improvement from drinking green tea. one large-scale population-based study found that
There is no clear evidence about green tea and green tea offered protection against the
breast cancer prevention. In one very large study, development of esophageal cancer, particularly
researchers found that drinking tea, green or any among women. Another population-based study
other type, was not associated with a reduced risk of found just the opposite; green tea consumption was
breast cancer. However, when the researchers broke associated with an increased risk of esophageal
down the sample by age, they found that women cancer. In fact, the stronger and hotter the tea, the
under the age of 50 who consumed 3 or more cups greater the risk. A number of epidemiologic studies
of tea per day were 37% less likely to develop have investigated the influence of consumption of
breast cancer compared to women who did not green tea on the risk of esophageal cancer [41].
drink tea. For more evidence additional studies are Given these conflicting results, more research is
required to elucidate the potential risk and needed before scientists can recommend green tea
associated mechanisms of action. for the prevention of esophageal cancer.

4.1.3 Ovarian Cancer 4.1.6 Lung Cancer

In a study done with ovarian cancer patients in While green tea polyphenols have been shown to
Table 1. Possible mechanisms for the anti-carcinogenic activity of green tea.
No Green Tea Component Possible Mechanism for Anti-carcinogenic Activity

1 EC
Anti-inflammatory
2 EGC Attenuation of oxidative stress
Induction of apoptosis
Catechins
Inhibition of RTK’s activation
3 ECG Inhibition of angiogenesis
Anti-metabolic syndrome
4 EGCG

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Table 2. Effect of the treatment with green tea for 30 days on the lipid profile of hypercholesterolemic
patients.

No Days Cholesterol (mg/dL) LDL (mg/dL)

1 0 270 ± 21.8 184 ± 17.1

2 15 196 ± 30.0 110 ± 21.9
3 30 247 ± 20.8 167 ± 16.3
4 60 278 ± 19.1 166 ± 20

inhibit the growth of human lung cancer cells in test should ask their doctors before drinking green or
tubes, few clinical studies have looked at the link black tea or taking tea supplements [44].
between drinking green tea and lung cancer in
people, and the studies that have been done show 4.1.9 Skin Cancer
conflicting results. One population-based study The main polyphenol in green tea is EGCG.
found that Okinawan tea, similar to green tea but Scientific studies suggest that EGCG and green tea
partially fermented, was associated with lower lung polyphenols have anti-inflammatory and anticancer
cancer risk, particularly among women. But a properties that may help prevent the development
second study found that green tea and black tea and growth of skin tumors. Hence it is work as anti-
increased the risk of lung cancer. More studies are carcinogenic agent [45]–[47]. Its anti-carcinogenic
needed before researchers can draw any conclusions activity due to some mechanistic effect is
about green tea and lung cancer. Green tea should summarized in Table 1 [35].
not be used by patients on bortezomib therapy [42].
4.2 Atherosclerosis
4.1.7 Pancreatic Cancer Population-based studies indicate that the
In one large-scale clinical study researchers antioxidant properties of green tea may help prevent
compared green tea drinkers with nondrinkers and atherosclerosis, particularly coronary artery disease
found that those who drank more tea was less likely [48]. Population-based studies are studied large
to develop pancreatic cancer. This was particularly groups of people over time and compared their
true for women, those who drank more green tea living in different cultures and diets. Researchers
were half as likely to develop pancreatic cancer as believe green tea reduces the risk of heart disease
those who drank less tea. Men who drank more tea by lowering cholesterol and triglyceride levels.
were 37% less likely to develop pancreatic cancer. Studies show that black tea has similar effects. In
However, it is not clear from this population-based fact, researchers estimate that the rate of heart
study whether green tea is solely responsible for attack decreases by 11% with consumption of 3
lowering pancreatic cancer risk [43]. More studies cups of tea per day.
are needed before researchers can recommend green
tea for the prevention of pancreatic cancer. 4.3 High Cholesterol
Research shows that green tea lowers total
4.1.8 Prostate Cancer cholesterol and raises HDL cholesterol in both
Laboratory studies have found that green tea animals and people. One population-based study
extracts prevent the growth of prostate cancer cells found that those who drink green tea are more
in test tubes. A large clinical study in Southeast likely to have lower total cholesterol than those who
China found that the risk of prostate cancer went do not drink green tea. Results from one animal
down with increasing frequency, duration, and study suggest that polyphenols in green tea may
quantity of green tea consumption. However, both block cholesterol from being absorbed in the
green and black tea extracts also stimulated genes intestine and also help the body get rid of
that cause cells to be less sensitive to chemotherapy cholesterol. In another small study of male smokers,
drugs. People who are undergoing chemotherapy researchers found that green tea significantly

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reduced blood levels of harmful LDL cholesterol
shown in Table 2 [21][49]. 4.6 Weight Loss
Clinical studies suggest that green tea extract
4.4 Diabetes may boost metabolism and help burn fat. One study
Green tea has been used traditionally to control found that the combination of green tea and caffeine
blood sugar levels. Animal studies suggest that improved weight loss and maintenance in people
green tea may help to prevent the development of who were overweight and moderately obese [52].
diabetes (type-1) and slow the progression once it Studies shows consumption of green tea lowers
has developed. In people with diabetes (type-1), LDL but not HDL cholesterol and leads to weight
their bodies make little or no insulin, which helps loss.
convert glucose or sugar into energy. Green tea may
help regulate glucose in the body. Research also 4.7 Other Uses
suggests that regular consumption of green tea may Preliminary studies suggest that drinking green
help manage diabetes (type-2) [50]. tea can help prevent various diseases and improves
health of living creatures [17][53]–[65]. It may also
4.5 Liver Disease be useful in inflammatory diseases, such as arthritis.
Population-based studies have shown that those Research suggests that green tea may help arthritis
who drink more than 10 cups of green tea per day by reducing inflammation and slowing the
are less likely to develop liver problems. Green tea breakdown of cartilage. Chemicals in green tea may
also seems to protect the liver from the damaging help treat genital warts, treat dermatologic
effects of toxic substances such as alcohol. Animal conditions, and prevent symptoms of colds and flu.
studies have shown that green tea helps protect Green tea may play a role in preventing Parkinson
against liver tumors in mice. It is important to note disease, cognitive decline, and osteoporosis. It also
that 10 cups of green tea a day could cause works on various microorganisms and prevents
problems due to high levels of caffeine [51]. various antimicrobial disease [15]. Studies also
Results from several animal and human studies show that drinking green tea influences
suggest that catechins, may help treat viral hepatitis, psychopathological function, cognition and brain
an inflammation of the liver. In these studies, function of human being [66].
catechin was used by itself in very high amounts. Its activity for antiphotoaging, stress resisting,

Table 3. Possible interaction of medication with consumed green tea.

No Medication Purpose of Medication Possible Effect(s) with Consumed Green Tea

For irregular unstable

1 Adenosine Inhibit the action of adenosine
heart-beat

2 Beta-Lactum Antibiotic Makes bacteria less resistant

3 Benzodiazepines Anxiety May reduce the sedative effect

4 Chemotherapy Cancer Less sensitive to drugs

Monoamine Oxidase
5 Depression Increase in blood pressure
Inhibitors

Quinolone
6 Antibiotic Increase the risk of side effects
Antibiotics

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neuroprotection and autophagy is also very well liver problem and discontinue use and consult a
studied [14]. The composition of green tea healthcare practitioner if you develop symptoms of
preparations that most closely reflects that of a liver trouble, such as abdominal pain, dark urine, or
traditional infusion is safe. Preparations based on jaundice (yellowing of the skin or eyes) [10][73].
concentrated extracts or containing high levels of
individual constituents, EGCG, may require health- 6. CONCLUSIONS
based guidance values to assure their safe use [10].
The present review has discussed the positive
5. SAFETY AND TOXICITY and negative impact of green tea on human health.
Though studies have provided enough evidence for
The use of herbs is a time-honored approach to favorable effects related to heart diseases,
strengthening the body and treating disease. cholesterol, blood fats, endometrial cancer, ovarian
However, herbs contain active substances that can cancer and high blood pressure. However, there is
trigger side effects and interact with other herbs, insufficient evidence for blood disorders, bladder,
supplements, or medications. For these reasons, colon, breast and cervix cancer and other ailments.
people should take herbs with care, under the Studies which report conflicting results may be
supervision of a practitioner knowledgeable in the presumed due to perplexing factors such as
field of botanical medicine [67]. countable consumption, temperature, race, sex, age,
People with heart problems or high blood lifestyle and genetic history. More attempts for
pressure, kidney problems, liver problems, stomach clarification are still required to establish the
ulcers, and psychological disorders, particularly reported effects.
anxiety, should not take green tea. Pregnant and
breastfeeding women should also avoid green tea AUTHOR INFORMATION
[68].
People with anemia, diabetes, glaucoma, or Corresponding Author
osteoporosis should ask their health care provider Sarika Malik — Chemistry Department, Ramjas
before drinking green tea or taking an extract. College, University of Delhi, Delhi-110007
People who drink large amounts of caffeine, (India);
including caffeine from green tea, for long periods Email: sarikamalik@ramjas.du.ac.in
of time may experience irritability, insomnia, heart
palpitations, and dizziness. Caffeine overdose can Author
cause nausea, vomiting, diarrhea, headaches, and Sonia Ratnani — Chemistry Department,
loss of appetite [69]. Ramjas College, University of Delhi, Delhi-
Medications for treatment such as adenosine, 110007 (India);
beta-lactum, benzodiazepines, beta-blockers, and
proponal. can interfere and cause adverse effects. ACKNOWLEDGEMENT
Following Table 3 gives the possible interaction of
medication with consumed green tea [70]. Authors are thankful to the Chemistry
As reported, ingestion of excess green or Department, Ramjas College, University of Delhi,
associated preparations can cause one of the most Delhi.
detrimental effects as hepatotoxicity [71][72]. As
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