The
Properties of Green Tea: Dietary and Health Benefits
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.
Using Tea in Synergy
·
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.
