http://en.wikipedia.org/wiki/Green_tea
Taxonomy
C. sinensis (L.)
Kuntze
History
•Green tea is made from the dried leaves of Camellia
sinensis , a perennial evergreen shrub. Green tea has a
long history of use, dating back to China approximately
5,000 years ago.
•Green tea has been used as traditional medicine in
areas such as India, China, Japan and Thailand to help
•everything from controlling bleeding and helping heal
wounds to regulating body temperature, blood
•sugar and promoting digestion.
Green or Black?
•Green tea and black tea are derived from the same leaf. The
difference lies in how they are processed.
•When making green tea the leaves are plucked processed
immediately to prevent them from fermenting.
•Unfermented leaves contain large amounts of catechins, which
are powerful disease fighters and potent antioxidants.
•When making black tea, the leaves are picked and are left to
ferment. This changes the chemical structure of the
catechins into substances called thearubigens and
theaflavins, which have some health benefits but not
nearly as many as the catechins.
Brewing and Dosage
• Generally, 2.25 grams of tea per 6 ounces of water, or
about one teaspoon of green tea per cup, should be used.
• The average 6-ounce cup of green tea contains between
50 and 100 mg catechins.
• Most studies have concluded that you need 3-10
cups of green tea per day, or up to 1,000 mg. of
catechins in order to get the healthy benefits of
green tea
What Can Green Tea Prevent?
•Alzheimer’s disease
•Parkinson’s disease
•Cancer
• HIV
•multiple sclerosis
•LDL cholesterol
•Cardiovascular disease
•Raise metabolism
•insulin sensitivity
•hypertension
•tooth decay
•cholera
• And anything else you can think of….
Active Constituents[25]
Catechins [25]
• family of flavan-3-ols
– Sub group of flavanoids –technically not a
flavanoid due to lack of carbonyl group
• Are polyphenyl groups which have
been shown to have anti-oxidant and
anti-carcinogenic properties
• Catechins make up slightly less than
30% of dry weight
Catechins
• Epicatechin and
epogallocatechin most
commonly found in nature
• Epigallocatechin gallate
most frequent catechin
found in Green Tea
– Thought to hold most
antioxidant activity
– Gallic acid attached to
catechin
• Gallic acid found freely and
within tannins in many other
plants
Other Active Components
• Vitamin C
– antioxidant
• B Vitamins
– Metabolize carbohydrates
– Manufacture fatty acids and amino acids
• Vitamin E
– Antioxidant
• Fluoride
– Protection of tooth decay and gum disease
– Caffeine (3-4%)
– About a quarter of that of coffee
The Asian Paradox
[1]
• Next to Green Tea, cigarettes are mostly
widely consumed product in Asia
• Asians have some of the lowest cardio-related
death rates in the world
• Clinical studies have been performed to view
different aspects and health benefits of green
tea that lead to this paradox
Pharmacokinetics
[2]
• Changes in blood count and blood
chemistry profiles not significant in
individuals given EGCG dosages
• Non-significant difference in
amount of tea catechins found
after initial dosage and 4 weeks
later after daily regimen of EGCG at
800 mg/day and 400 mg/ day
• >60% increase in the systemic
availability of free EGCG after
chronic green tea polyphenol
administration at 800 mg/day
Pharmacokinetics
[2]
• Side Effects found in this study:
– Excess gas
– Upset stomach
– Heartburn
– Abdominal pain
– Dizziness
– Headache
– Muscle pain
• All reported as mild events
Pharmacokinetics
[3]
• Found that EGCG levels rose significantly at
about 3 hours and peaked between 8-15
hours after a single dosage
• 90% of EGC and EC excreted in urine between
0-8 hours
• Supports other study with similar results
Clinical Trials; Heart Disease
• In a double-blinded, randomized, placebo-controlled trial ,240
adults were given either theaflavin-enriched green tea extract
in form of 375mg capsule daily or a placebo. After 12 weeks,
patients in the tea extract group had significantly LDL
cholesterol and total cholesterol (16.4% and 11.3% lower than
baseline, p<0.01) than the placebo group [4]
• A meta-analysis examining the effect of green tea on
cardiovascular heart health found a decrease in the rate of
heart disease outcomes with increasing tea consumption. [5]
However, two studies from the United Kingdom [6][7] and
two studies from the United States [8][9] indicated an
increased risk with increasing tea consumption, whereas the
other studies indicated a decrease in risk.
Clinical Trials; Cancer
• EGCG and other tea polyphenols inhibited
growth of human lung cancer cell line, PC-9
cells with G2/M arrest. [10]
• Many studies have studied the inhibitory
effects of EGCG and green tea extract on
carcinogenesis in various organs of rodents
[11][12][13]
Skin Cancer[14]
• 2 groups of lab mice (30 each) subjected to
equal amounts of UVB radiation
• One group treated with 1.25% green tea
drinking water and other with 2.5% green tea
drinking water, control with distilled water
• Decreased number of skin tumors and
substantially reduced size of tumors
Skin Cancer[14]
Breast Cancer [15]
• In vitro
– green tea catechins inhibits proliferation of ER-positive
MCF-7 breast cancer cells
• In vivo
– Mice studied had increased levels of catechins in
mammary fat pads and levels were relative to how
much tea was administered to each group
• In both aspects of the study catechins used with
tamoxifen, a orally active selective estrogen
receptor modulator, showed the best results in
comparison to catechins or tamoxifen alone
Clinical Trials; Obesity
• Mice that were fed high fat diets supplemented with tea
catechins for 11 months resulted in a significant reduction of
diet-induced weight gain [16]
• Ingestion of tea catechins stimulated O2 consumption and
energy expenditure and decreased the respiratory quotient in
humans. [17]
• Injection of EGCG modulates appetite and reduces food
intake through the leptin receptor-independent pathway in
rats.[18]
Clinical Trials; Diabetes
• Green tea supplementation ameliorates insulin resistance
and increases glucose transporter IV content in a fructose-fed
rat models of diabetes [21]
• Some studies have shown that plasma glucose levels in
diabetic rats are lowered when the rats are given (-)
epicatechin [19] [20]
Gastrointestinal
[22]
• Test of each catechin found in green tea to find which best
treats GI infection by Helicobacter pylori
– chronic gastritis, peptic ulceration, and gastric cancer
• In vivo study
–
–
–
–
–
–
Mongolian gerbils inoculated with equal levels of H. pylori
fed different diet containing (0, .5, 1, or 2%) catechins for 2 weeks
H. pylori was eradicated in about 10% of the gerbils
In ones not eradicated, 10-36% decrease of H. pylori
Similar to success rate in human cell in vitro studies with antibiotics
More studies need on impacts of catechins on H. pylori other than
eradication
Epidemiological Studies[23]
• Few have been done and ones completed take
place in Asia
• So many variables to account for, e.g.
smoking, alcohol consumption, diet, exercise
it is hard to derive results
• One study looked at over 18000 men from
Shanghai and said there was a slight decrease
in cancer rates, but results seem to be
unverifiable due to high variability of subjects
Contraindications[24]
• Caffeine only substance that has potential to
do harm
– Pregnant/nursing women should limit caffeine
intake
• Should not be taken if used with Warfarin
– Vitamin K interacts with anticoagulation
References
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disease.” Journal of American College of Surgeons. 2006. 202:5, pp. 813825.
2. Chow, Sherry, et al. “Pharmacokinetics and safety of green tea polyphenols after
multiple-dose administration of epigallocatechin gallate and polyphenon E in healthy
individuals.” Clinical Cancer Research. 2003. 9, pp. 3312-3319.
3. Lee, M.J., et al. “Pharmacokinetics of tea catechins after ingestion of green tea and
epigallocatechin-3-gallate by humans: formation of different metabolites and
individual variability.” Cancer Epidemiol Biomarkers Prev. 2002. 10:1, pp.10251032.
4. David J. Baron et al. “Cholesterol-Lowering Effect of a Theaflavin-Enriched Green
Tea
Extract.” Arch Intern Med. 2003.163:1448-1453.
5. Ulrike Peters et al. “Does Tea Affect Cardiovascular Disease? A Meta-Analysis.”
American Journal of Epidemiology. 2001. 154:6 pp. 495-503.
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catechin.“ Am J Clin Nutr. 2000. 72, pp. 1232 – 1234.
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potential antidiabetic agent.” J Nat Prod. 1988. 46, pp. 232–234.
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islets of
pancreas in alloxan induced diabetic rats by (-)-epicatechin.” Life Sci.
1982. 31, pp. 2693–
2697.
21. Lucy Sun Hwang et al. “Green tea supplementation ameliorates insulin resistance
and
increases glucose transporter IV content in a fructose-fed rat model.”
European Journal
of Nutrition. 2004. 43:2, pp.116-124.
22. Mabe, Katsuhiro, et al. “In Vitro and In Vivo Activities of Tea Catechins against
Helicobacter pylori.” Antimicrobial Agents and Chemotherapy. 1999. 43:7,
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