Green Tea – Magic Drink
Today, millions of
people drink tea around the world, and it is now considered as one of the most
widely consumed beverages in the world, second after drinking water. Multiple
studies confirm the Eastern Medicine conclusions that drinking green tea
(Camellia Sinesis) in particular has many outstanding benefits for your health.
Green tea is a botanical that has been shown to protect people from many types
of cancer, reduces inflammation, helps protect the liver, boosts metabolism and
shows many other positive health effects.
There are three main
varieties of tea — green, black, and oolong. The difference between the teas is
in their processing. Green tea is made from unfermented leaves and reportedly
contains the highest concentration of powerful antioxidants called polyphenols.
Antioxidants are
substances that scavenge free radicals — damaging compounds in the body that
alter cells, tamper with DNA (genetic material), and even cause cell death.
Free radicals occur naturally in the body, but environmental toxins (including
ultraviolet rays from the sun, radiation, cigarette smoke, and air pollution)
also give rise to these damaging particles. Many scientists believe that free
radicals contribute to the aging process as well as the development of a number
of health problems, including cancer and heart disease. Antioxidants such as
polyphenols in green tea can neutralize free radicals and may reduce or even
help prevent some of the damage they cause.
Green tea has been
consumed throughout the ages in India, China, Japan, and Thailand. In
traditional Chinese and Indian medicine, practitioners used green tea as a
stimulant, diuretic (to promote the excretion of urine), astringent (to control
bleeding and help heal wounds), and to improve heart health. Other traditional
uses of green tea include treating flatulence (gas), regulating body
temperature and blood sugar, promoting digestion, and improving mental
processes.
Green tea and
pancreatic cancer
Green tea has so many health related advantages for humans,
so it is not surprising that medical scientists are trying to look if it can be
useful for pancreatic cancer prevention. Pancreatic cancer is famous by its
difficulties and diagnostics, so in many cases, it is identified at the moment
when the tumor is incurable. Therefore, it so important to identify ways of
preventing this deadly disease, or, actually, decreasing the risk of getting
it.
In the recent article "Green tea and the risk of pancreatic cancer and colon cancer," the group of researchers
from Columbia University examined the question of the effectiveness of green
tea as a remedy against certain types of cancer. This is a preliminary study and researchers admitted that
the results are not statistically conclusive yet, suggesting to complement it
with additional researches on animal and human. However, the results are quite
positive, and may lay a trail to the future studies and consumer
recommendations.
Testing the hypothesis of the ability of green tea regular consumption
to influence the risk of getting several types of cancer, the researchers conducted extensive study in Shanghai,
China. The research team found the direct correlation between drinking green
tea and cancer development rates: the higher consumption of green tea led to
the lower the risk of cancer.
Therefore, it seems that green tea can, in fact, reduce the incidence of both colon and pancreatic cancer, which is
especially important for the people having certain predisposition to the tumor
development.
Another study has been performed, looking for the causal
relationship between green tea drinking and risk of development of pancreatic
cancer in particular. And the results were also encouraging, showing the
substantial health related benefits. Interesting that the study showed general difference
in results - significantly higher positive effect has been observed among
females, where the risk of pancreatic cancer decreased 50%, while male green
tea drinkers has shown just 37% of the risk decrease.
Definitely, more studies are needed, but based on these
results, and general benefits of Green Tea, I would say that it is highly
recommended to be included in your daily diet, especially when you read its
health benefits for other functional systems of your body and mind.
Other health benefits
Bladder cancer
Only a few clinical
studies have examined the relationship between bladder cancer and green tea
consumption. In one study that compared people with and without bladder cancer,
researchers found that women who drank black tea and powdered green tea were
less likely to develop bladder cancer. A follow-up clinical study by the same
group of researchers revealed that bladder cancer patients (particularly men)
who drank green tea had a substantially better 5-year survival rate than those
who did not.
Breast cancer
Clinical studies in
animals and test tubes suggest that polyphenols in green tea inhibit the growth
of breast cancer cells. In one study of 472 women with various stages of breast
cancer, researchers found that women who consumed the most green tea
experienced the least spread of cancer (particularly premenopausal women in the
early stages of breast cancer). They also found that women with early stages of
the disease who drank at least 5 cups of tea every day before being diagnosed
with cancer were less likely to suffer recurrences of the disease after
completion of treatment. However, women with late stages of breast cancer
experienced little or no improvement from drinking green tea. In terms of
breast cancer prevention, the studies are inconclusive.
Ovarian cancer
In a clinical study conducted on ovarian
cancer patients in China, researchers found that women who drank at least one
cup of green tea per day survived longer with the disease than those who didn’t
drink green tea. In fact, those who drank the most tea, lived the longest.
Prostate cancer
Laboratory studies have found that green tea
extracts prevent the growth of prostate cancer cells in test tubes. In a large
clinical study conducted in Southeast China researchers found that the risk of
prostate cancer declined with increasing frequency, duration and quantity of
green tea consumption.
Skin cancer
The main polyphenol
in green tea is epigallocatechin gallate (EGCG). Scientific studies suggest
that EGCG and green tea polyphenols have anti-inflammatory and anti-cancer
properties that may help prevent the onset and growth of skin tumors.
Inflammatory Bowel Disease (IBD)
Green tea may help
reduce inflammation associated with Crohn’s disease and ulcerative colitis, the
two types of IBD. If green tea proves to be helpful for preventing colon
cancer, this would be an added benefit for those with IBD because they are at
risk for colon cancer.
Diabetes
Green tea has been
used traditionally to control blood sugar in the body. Animal studies suggest
that green tea may help prevent the development of type 1 diabetes and slow the
progression once it has developed. People with type 1 diabetes produce little
or no insulin, a hormone that converts glucose (sugar), starches, and other
foods into energy needed for daily life. Green tea may help regulate glucose in
the body. A few small clinical studies have found that daily supplementation of
the diet with green tea-extract powder lowered the hemoglobin A1c level in
individuals with borderline diabetes.
Liver disease
Population-based
clinical studies have shown that men who drink more than 10 cups of green tea
per day are less likely to develop disorders of the liver. Green tea also seems
to protect the liver from the damaging effects of toxic substances such as
alcohol. Animal studies have shown that green tea helps protect against the
development of liver tumors in mice.
Results from several
animal and human studies suggest that one of the polyphenols present in green
tea, known as catechin, may help treat viral hepatitis (inflammation of the
liver from a virus). In these studies, catechin was isolated from green tea and
used in very high concentrations. It is not clear whether green tea (which
contains a lower concentration of catechins) confers these same benefits to
people with hepatitis.
Heart Disease
Green tea also
benefits your heart. A Japanese study found that drinking four cups of green
tea may reduce the severity of coronary heart disease. A similar Dutch study
found that green tea consumption correlated with less clogging of the coronary
arteries. Because the antioxidants in green tea are dilators, consuming more
green tea improves the flexibility of blood vessels and may make them less
likely to become clogged.
Weight loss
Clinical studies
suggest that green tea extract may boost metabolism and help burn fat. One
study confirmed that the combination of green tea and caffeine improved weight
loss and maintenance in overweight and moderately obese individuals. Some
researchers speculate that substances in green tea known as polyphenols,
specifically the catechins, are responsible for the herb’s fat-burning effect. Studies
in Japan and the Netherlands have supported this claim. Participants in the
Dutch study who drank the most green tea lost the most weight and body fat, had
lower blood pressure, and had lower “bad” cholesterol.
Dosage
Depending on the brand, 2 - 3 cups of green tea per day (for
a total of 240 - 320 mg polyphenols) or 100 - 750 mg per day of standardized
green tea extract is recommended. Caffeine-free products are available and
recommended.
Precautions
The use of herbs is a time-honored approach to strengthening
the body and treating disease. However, herbs contain active substances that
can trigger side effects and interact with other herbs, supplements, or
medications. For these reasons, people should take herbs with care, under the
supervision of a practitioner knowledgeable in the field of botanical medicine.
People who drink excessive amounts of caffeine (including
caffeine from green tea) for prolonged periods of time may experience
irritability, insomnia, heart palpitations, and dizziness. Caffeine overdose
can cause nausea, vomiting, diarrhea, headaches, and loss of appetite. If you
are drinking a lot of tea and start to vomit or have abdominal spasms, you may
have caffeine poisoning. If your symptoms are severe, lower your caffeine intake
and see your health care provider.
Possible Interactions
If you are being treated with any of the following
medications, you should not drink green tea or take green tea extract without
first talking to your health care provider:
Adenosine -- Green tea may inhibit the actions
of adenosine, a medication given in the hospital for an irregular (and usually
unstable) heart rhythm.
Antibiotics, Beta-lactam -- Green tea may
increase the effectiveness of beta-lactam antibiotics by reducing bacterial resistance
to treatment.
Benzodiazepines -- Caffeine (including caffeine
from green tea) has been shown to reduce the sedative effects of
benzodiazepines (medications commonly used to treat anxiety, such as diazepam
and lorazepam).
Beta-blockers, Propranolol, and Metoprolol --
Caffeine (including caffeine from green tea) may increase blood pressure in
people taking propranolol and metoprolol (medications used to treat high blood
pressure and heart disease).
Blood Thinning Medications (Including Aspirin) --
People who take warfarin, a blood thinning medication, should not drink green
tea. Since green tea contains vitamin K, it can make warfarin ineffective.
Meanwhile, you should not mix green tea and aspirin because they both prevent
platelets from clotting. Using the two together may increase your risk of
bleeding.
Chemotherapy -- The combination of green tea and
chemotherapy medications, specifically doxorubicin and tamoxifen, increased the
effectiveness of these medications in laboratory tests. However, these results
have not yet been demonstrated in studies on people. On the other hand, there
have been reports of both green and black tea extracts stimulating a gene in
prostate cancer cells that may cause them to be less sensitive to chemotherapy
drugs. Given this potential interaction, people should not drink black and
green tea (as well as extracts of these teas) while receiving chemotherapy for
prostate cancer in particular.
Clozapine -- The antipsychotic effects of the
medication clozapine may be reduced if taken fewer than 40 minutes after
drinking green tea.
Ephedrine -- When taken together with ephedrine,
green tea may cause agitation, tremors, insomnia, and weight loss.
Lithium -- Green tea has been shown to reduce
blood levels of lithium (a medication used to treat manic/depression).
Monoamine Oxidase Inhibitors (MAOIs) -- Green
tea may cause a severe increase in blood pressure (called a "hypertensive
crisis") when taken together with MAOIs, which are used to treat
depression. Examples of MAOIs include phenelzine and tranylcypromine.
Oral Contraceptives -- Oral contraceptives can
prolong the amount of time caffeine stays in the body and may increase its
stimulating effects.
Phenylpropanolamine -- A combination of caffeine
(including caffeine from green tea) and phenylpropanolamine (an ingredient used
in many over-the-counter and prescription cough and cold medications and weight
loss products) can cause mania and a severe increase in blood pressure. The FDA
issued a public health advisory in November 2000 to warn people of the risk of
bleeding in the brain from use of this medication and has strongly urged all
manufacturers of this drug to remove it from the market.
Useful Tips
- Allow tea to steep for three to five minutes to bring out its catechins.
- The best way to get the catechins and other flavonoids in tea is to drink it freshly brewed. Decaffeinated, bottled ready-to-drink tea preparations, and instant teas have less of these compounds.
- Tea can impede the absorption of iron from fruits and vegetables. Adding lemon or milk or drinking tea between meals will counteract this problem.
Sources and Additional
Information:
