The properties and benefits of green tea have been known for centuries
in many Asian civilizations. However, green tea has become increasingly popular
in the west only in recent times, and it is only now that mainstream science
has started to take notice of the long purported health benefits of green tea
consumption.
Several key research studies have gathered evidence in support of many
of these claims. Studies have shown that green tea consumption can have
potentially positive impacts on cardiovascular health, can help in the
reduction of stress related health conditions and may also have a role in
preventing certain types of cancer.
This short report focuses on the effects of green tea consumption on
human health, as claimed by traditional wisdom, as well as significant findings
in recent scientific studies, with a particular emphasis on its role in weight
loss. The report will also take a look at combining the effects of green tea,
with other teas, under the process known as synergy.
Introduction
Tea, whether it is black, green or white, originates from the leaves of
different varieties of the plant Camellia
Sinensis. The difference between different types of tea (green tea, black
tea, white tea, oolong tea etc.) does not lie in the species of the plant
itself, but in the way the tea leaves are processed.
Green tea leaves undergo minimal oxidation as opposed to black tea
leaves, which helps it retain a high proportion of its anti-oxidant content.
While, there are many ways in which green tea is grown as well as processed,
the common factor between all these ways is that they ensure that polyphenols
and anti-oxidants are retained to the maximum.
Green tea in particular contains a high amount of natural polyphenols
known as flavonoids, which have become increasingly interesting to researchers
the world over due to their beneficial properties. Green tea is also rich in
minerals like chromium, zinc and manganese, and a good source of vitamin C.
The Known Health Benefits of Green Tea
Green tea has a very long history, especially in China, as Camellia Sinensis is native to this
region. So long has this brew been known as an agent of good health, that it
has been an integral part of ancient Chinese culture for over 4000 years.
It has been traditionally known to improve overall health and well
being, stave off disease, and maintain youth. More specifically, green tea is
thought to improve blood circulation, and maintain good heart health. As it is
thought to improve the circulatory system of the body, it is also thought to
ward off cardio-vascular diseases like angina and stroke, as well as other
conditions such as diabetes mellitus.
According to traditional Chinese wisdom, green tea is also a stress
buster and helps calm the nerves. It is known to be generally good for mental
wellbeing and is thought to help keep the mind nimble and alert.
Green tea is traditionally thought to have anti-ageing properties, both
mentally as well as physically. By keeping the mind agile and skin supple and
youthful looking, and the body healthy, green tea is thought to promote
longevity.
Although these claims have been made for thousands of years, it is only
with the progress of modern science and medicine that we are able to test them
and understand the mechanisms which are actually at work.
Let’s look at some specific research and findings on the effects of
green tea on health.
Research Findings on the Effects of Green Tea
Green Tea is rich in naturally occurring anti-oxidants known as
salubrious polyphenols. The beneficial properties of these anti-oxidants have
been known to science for some time now: some of which include boosting
immunity, anti-ageing effects and anti-cancer properties.
With the help of research we have now come to know that the
anti-oxidants in green tea fight off harmful free radicals in the body, an
action which has numerous positive effects on health.
Effects on
Cardio Vascular Health
Research done specifically on green tea consumption suggests that
ingestion of green tea, either in the form of tea or its extract, can reduce
the risk of heart disease, and other cardio vascular problems such as angina
and stroke.
·
In a case control study conducted in Japan, subjects
who consumed one or more than one cup of green tea per day had a reduced risk
of subarachnoid hemorrhage by 26% and 44% respectively than subjects who did
not consume the green tea.
Green tea is known to improve the health and condition of the cells that
line the walls of arteries – known as endothelial cells. Studies suggest that
due to its anti-oxidation properties, it can help in keeping these cells
healthy and minimize the build-up of plaque in the blood vessels. This finding
has major implications for heart disease as well as blood pressure-related
conditions.
Findings from studies on the relationship between green tea consumption
and cholesterol levels in the body suggest that green tea may help reduce
levels of bad cholesterol (Low Density Lipo-protein Cholesterol) in humans, by
reducing the absorption of cholesterol in the gut.
·
A recent study conducted by a team from the University
of Birmingham found that the rates of fat oxidation in subjects who ingested
green tea extract were 17% higher than in subjects who were given a placebo.
This indicates that green tea consumption is linked to weight reduction and
this has implications for many illnesses, including cardiovascular diseases.
Stress
Reduction and Mental Wellbeing
Green tea consumption seems to help reduce stress and the symptoms of
stress related disorders.
·
A 2009 Japanese study published in the American Journal of Clinical Nutrition
found that increased and more frequent intake of green tea in subjects was
associated with a lower incidence of depression and symptoms related to
depression.
Several other studies have suggested that green tea may have a positive
association with mental wellbeing and may also help combat the effects of
stress. Significantly, some studies have also linked regular consumption of
green tea with a reduced risk of developing Alzheimer’s.
Green Tea
and Cancer
Green tea contains naturally occurring anti-oxidants known as flavonoids
in abundance. Naturally occurring anti-oxidants are thought to have anti-carcinogenic
properties and research is still being undertaken to understand more about
these properties. Based on current findings, flavonoids are thought to include
properties that may inhibit tumor growth and invasion.
·
A study undertaken in China studied the eating habits
of a large cohort of Chinese women. The findings showed that the regular consumption
of mushrooms in combination with green tea was linked to a staggering 90% lower
occurrence of breast cancer.
Effects on
Immunity
·
Green tea has long been associated with longevity and
improved immunity. Many recent studies have corroborated with this claim. An
important study by a team at the Linus Pauling Institute, from Oregon State
University, has shown that EGCG, a key anti-oxidant present in Green tea, has a
strong ability to boost the immune system by increasing the regulatory T cells
in the body.
Effects of
Green Tea Consumption on Weight Loss
There has been a lot of interest in scientific circles in the effect
green tea consumption can have on metabolism and fat reduction. Studies have
found that green tea can reduce the amount of bad cholesterol and increase fat
oxidation by a significant degree.
·
A study conducted in 2005 by the Division of
Cardiovascular Medicine at the Vanderbuilt University Medical Center in
Nashville, Tennessee found that subjects given enriched green tea extract for a
specific period had over 16% lower levels of LDL than the baseline as compared
to the subjects that were given a placebo drug.
·
Findings
of a 1999 study published in the American
Journal of Clinical Nutrition showed that green tea has strong thermogenic
properties. Thermogenic substances boost metabolism which causes more calories
to burn. The study found that green tea caused a much higher level of fat
oxidation than could be attributed merely to its fat content. It was found that
as much as 4% of the overall energy expenditure in 24 hours could be attributed
to green tea extract. This expenditure was observed to be taking place during
the day. Since the body’s own rate of burning calories (thermogenesis)
contributes to 8-10% of daily energy expenditure, the burning of calories
caused by green tea translated to a staggering 35-43% increase in day time
thermogenesis!
·
In a 2003 study conducted in Taiwan on 1210 subjects,
it was found that test subjects who had regularly consumed tea for more than
ten years had a smaller waist circumference and waist to hip ratio, and lower
percentage of body fat. Out of these subjects, only 4% consumed regular black
tea, and 96% consumed either green or oolong tea.
·
In a controlled study conducted in France in 2001, the
effect of green tea extract was studied on 70 overweight men for 12 weeks. The
findings showed a 4.6% decrease in overall body weight. The researchers also
observed a reduction of the waist to hip ratio by 4.5% in the test subjects.
·
In a Taiwanese study conducted in 2000, the effects of
green tea consumption on fat absorption in rats fed on a high sugar diet were
observed. It was seen that green tea lowered the levels of fat storage in the
liver and heart, and reduced apparent fat absorption.
The
significant findings of these studies, as well as other key studies suggest
that green tea has significant potential to help in fat reduction and weight
loss.
·
Different
teas such as green tea, Oolong tea, Pu-erh tea and white tea are all produced
from the tea plant. As such, all the teas possess some basic characteristics
that are similar to each other.
·
For
instance all teas contain polyphenols, which have been shown by several studies
conducted worldwide to be beneficial in weight loss and maintaining cardio vascular
health, and preventing obesity.
·
However,
each tea also has its own unique strengths and is not quite the same as the
other tea. For instance, studies have shown green tea to be very effective in
lowering fat absorption in the body, while Pu-erh tea is effective in
suppressing hunger. Both these properties can be very useful in controlling
weight gain and preventing obesity.
·
Hence,
it may be most effective to take the teas in the right blends or combinations
in order to maximize their benefits. This is what is known as synergy.
Side Effects
of Green Tea Consumption
Being a completely natural substance, green tea when consumed in
moderation or as prescribed, either in tea form or as an extract, does not have
any known harmful side effects.
Pharmacological
evidence does show that green tea anti-oxidants in very high concentrations can
cause oxidative stress and liver toxicity. It is important to be aware of this
fact, and exercise caution when using any commercial herbal products made from
green tea extract.
Summary
Green tea has quite an impressive list of health benefits, both claimed
by traditional knowledge and wisdom, as well as those that are proved and being
proved by scientific research.
Its health effects are traditionally thought to include boosting
immunity, anti-ageing, stress reduction and the promotion of overall good
health. Many claims have received scientific backing by various studies, and
the strength of evidence for the numerous benefits of green tea is increasing.
Some important findings have shown that green tea improves circulation,
helps reduce bad cholesterol levels, and significantly reduces the risk of
cardio vascular illness. Studies have also suggested green tea may have anti-carcinogenic
properties against certain cancers, and may also have a role in preventing Alzheimer’s.
Several studies have shown that green tea plays
a significant role in increased fat oxidation by stimulating metabolism, and
therefore has important implications for weight loss, and preventing obesity.
Taking green tea extract in combination with certain other herbal teas can be a
highly effective agent of weight loss and fat reduction and this is known as
synergy.
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