Tea and Health
The ancient leaf known as tea, cha, t’e (tay), or for you latin buffs:
camellia sinensis
Black Tea | Green Tea | Oolong
Tea
1. Black Tea. Green tea was first
made and enjoyed as early as 2,737 BCE and since then it has been prized for
its medicinal qualities and stimulating effect. But it was not until 1,644
CE (over four thousand years later) that controlled fermentation was perfected
and a consistent quality of black and oolong tea was produced.
Black tea is made by first withering the leaves in special withering troughs
where they are dried until the moisture content is reduced to about 60 percent.
At this point the leaves are rolled in a process that bruises them and breaks
the cell membranes so that the phytochemicals that are contained within the
cells can interact. This begins the fermentation process. Once the polyphenols
mix with the air, the leaves darken and change, first from green to brown
or red, and then from brown or red to black. Once the fermentation process
is finished, the leaves are heated and dried until only about 3% of the original
moisture is left. Black tea can be stored in this dry state for up to two
years before taste and nutritional content begin to deteriorate.
Black tea contains less Catechins than Green Tea. Catechins are the flavonoids
that have been intensively investigated for their ability to prevent cancer
and heart disease. Catechins are antioxidants and may combat lipid peroxidation
within the cell membranes that line arterial walls and thereby reduce the
formation of arteriosclerosis plaques which are a significant factor in cardiovascular
disease. Detailed studies have been done to determine the actions of Catechins
in the human body. We know that almost 50% of radio-labeled Catechins given
to subjects as a drink were latter excreted in the a metabolized form in the
urine This means that the Catechins were absorbed by the digestive system,
were transported in the blood, interacted chemically with various oxidizing
compounds in the body, and then were finally removed from the blood and excreted
in the urine.
Though Black Tea contains less Catechins than Green Tea it contains significantly
higher levels of Theaflavins and Thearubigins. These polyphenols seem to produce
significant health benefit, although they have been less intensively studied
that Catechins. For instance An
investigation in 2001 found no published evidence of the action of Theaflavins
and Thearubigins in the human body, however researchers familiar with the
action of these compounds in the digestive tract anticipate that they would
be easily absorbed either directly or through the action of intestinal flora.
Thearubigins make up about 10 to 20 percent of the total dry weight of black
tea while theaflavins contribute another 1 and 2 percent. 
Researchers at the Burnham Institute have identified polyphenols in green
and black teas that are potent inhibitors of a family of proteins implicated
in many types of cancer. The polyphenols inhibit the over production of the
proteins that keep cancer cells from dying. Thus they allow the bodies natural
anti-cancer mechanisms to work efficiently. This epidemiological evidence
has been supported by in vitro laboratory studies. 1.
Epidemiological evidence suggests that drinking black tea reduces the risk
of coronary heart disease, but until recently little experimental evidence
existed to show teas affect on blood cholesterol concentrations. A new study
looked at a small group of subjects who ate a carefully controlled diet that
included either five servings of black tea or a placebo beverage in a blinded
randomized crossover study that took place over a three week treatment period.
It was found that five servings of tea reduced total cholesterol 6.5%, LDL
cholesterol 11.1%, apolipoprotein B 5% and lipoprotein(a) 16.4%, compared
with the placebo that contained only caffeine. The study concluded that the
inclusion of black tea in a diet moderately low in fat reduces total and LDL
cholesterol by significant amounts and may, therefore, reduce the risk of
coronary heart disease 2.
A double-blind, randomized, controlled study of 240 men and women with high
cholesterol levels was recently carried out in China. Participants in the
12 week study were already on a low-fat diet and were randomly chosen to receive
either a placebo or a 375 mg soft gel capsule containing green and black tea
extracts enriched with the antioxidant theaflavin. The participants who received
the tea supplements had an average reduction in low density lipoprotein (LDL)
cholesterol of 16%. The capsule used in this study is an extract made up of
75 mg of theaflavins, the flavonoids from black tea, 150 mg of catechins the
flavonoids from green tea, and 150 mg of other tea antioxidants called polyphenols.
It is equivalent to 35 cups of high-quality black tea and 7 cups of green
tea. The author of the study, Dr. David J. Maron, commented that unlike statins
this product has not been proven to prevent heart attacks or stroke, or to
prolong life, but such tea extracts may offer alternatives for treating heart
disease with naturally derived substances 3.
Consumption of a high fat meal can produce a chemical chain reaction within
blood vessels which can temporarily impair their ability to dilate or widen,
a normal response to increased blood flow. However, antioxidants seem to prevent
this chain reaction. A recent study done at the University of Maryland Medical
Center by cardiologist Mary Corretti, M.D. found that drinking tea reduced
the impact of a high fat meal on blood vessel function. Participants in the
study included 30 healthy, adult, non-smoking volunteers, ages 20 to 55. On
three occasions, the volunteers ate a 900-calorie, fast food meal that contained
50 grams of fat. They also drank one of three beverages. Either a cup of iced
black tea, iced green tea or an iced liquid that resembled tea. The volunteers
were people who rarely drink tea. Only the tea relieved the arteries inability
to dilate.
Data from two 2001 studies also support the health benefits of drinking black
tea. The studies were presented June 16, 2001, at the first-ever Epidemiology
Congress 2001, a joint meeting of Canadian and American scientific societies.
The first paper, a national cross-sectional study of 1,764 women in Saudi
Arabia, showed that tea drinkers were 19% less likely to suffer from cardiovascular
disease. The Saudi women who consumed black tea had total cholesterol, triglycerides,
and low-density lipoprotein (LDL) measures that were significantly lower than
non-tea drinkers. The most marked reduction in blood lipid levels was observed
in women who consumed six or more cups of tea a day.
The second paper showed that tea consumption was associated with a lower risk
of rectal cancer in Moscow women. This population-based, case-control study
of 663 patients with rectal cancer and 323 randomly selected controls supported
tea's potential in the prevention of rectal cancer. The study found that higher
levels of tea drinking were associated with lower risk of rectal cancer among
the Moscow population. This association between tea consumption and the lower
risk of rectal cancer was stronger among Moscow women than in men. "The statistical
modeling of the Moscow data suggests that this difference in risk reduction
between genders can be partially explained by the overwhelming harmful effect
of alcohol consumption among Moscow men," said the studies author4.
2. Green Tea.
Green Tea was the only tea anyone knew about for thousands of years. Originally
it was made by picking the leaves off the tree and steeping them directly
in hot water. Emperor Shen Nung is credited with discovering the medicinal
uses of green tea and down through the years many others have expanded on
his early observations.
Unlike black and oolong teas, green tea receives very little processing, but
it is not accurate to say it is 'unprocessed." Without the right kind
of processing the natural enzymes within the tea leaves themselves begin the
fermentation process. Over the years tea growers and manufacturers have come
up with different ways to insure that green tea stays green. In China freshly
picked leaves are withered briefly and then heated in the sun or by directing
hot air over them. Then the leaves are heated in large dry woks to insure
even evaporation and consistent aroma and flavor. Once flavour and aroma have
been stabilized the leaves are shaped by rolling them into needle long spears
or tight pellets or balls.
In Japan steam is used in place of withering and air drying to stop the enzyme
action. The Japanese method uses dry heat only after the leaves are shaped
and because of this the color of the leaves tend to be greener. Hojicha is
a special Japanese green tea which is made by further roasting the dryed leaves
and stems to produce a nutty flavor and brown color.
White Tea.
White tea is a form of green tea that is made with even less processing. New
leaves and buds are picked and dried without withering, steaming, rolling
or fermentation. Consequentially white tea can have the highest concentration
of the phytochemicals considered to help prevent heart disease and cancer.
It is called white because the fine leaf-hairs remain clearly visible and
are not damaged by processing.
Health Benefits.
As discussed above in the Black Tea section, Green Tea has many health benefits
due to its high levels of Catechins. Green tea is also known to be very rich
in fluoride and EGCG.
Dr. Lester Mitscher, a medicinal chemistry professor at the University of
Kansas, published a study in 1997 that showed that green tea contains high
concentrations of epigallocatechin gallate (EGCG), the strongest known antioxidant.
EGCG is over 100 times more effective in neutralizing free radicals than vitamin
C and 25 times more powerful than vitamin E. Antioxidants are the molecules
demonstrated to prevent the kind of cellular damage that leads to cancer and
heart disease. 5
Green tea is one of the most studied natural products in the world today.
Controlled scientific studies from Europe, North America, Japan, China and
Australia suggest health benefits from regular consumption of it. Green Tea
is believed to help lower cholesterol, prevent heart disease, fight oral bacteria
and dental cavities, and contribute to healthy weight loss. Many Studies suggest
potential anticancer benefits of tea while others show that it works best
as a preventative measure and is not effective with cancer in advanced stages.6
According to an Australian team of researchers, drinking green tea can protect
women from developing ovarian cancer. The study shows that women who drank
at least a cup of green tea daily had a 39 percent lower risk of getting ovarian
cancer than those who did not drink the brew daily.7
Alexa Boer Kimball, M.D., M.P.H., assistant Professor and director of clinical
trials at Sanford Hospital and Clinics commenting on a recent study of Green
Tea extracts as a topical treatment noted that, "...studies with Green Tea
have shown it to be a powerful antioxidant that can help prevent photo-damage
in the skin."
her new study which did not find visible signs of rejuvenation over an eight
week period, did, never the less, demonstrate that the the topical tea extract
promoted elastic tissue remodeling. The change in skin elasticity was significant
and demonstrates that the extract had a positive effect, if not a curative
one.8
How Green Tea Works
A variety of tumours produce abnormally high levels of a cell called 67 LR.
67 LR cells have a receptor on them that is thought to be involved in the
spread of cancer through the body. Hirofumi Tachibana and his team at Kyushu
University in Japan have recently shown9 that
EGCG inhibits tumour cell growth by binding to the receptor on 67 LRcells.
Tachibana was able to demonstrate that lung cancer cells that have the receptor
slowed significaltly when exposed to EGCG at the concentrations reached in
the body after drinking just two or three cups of green tea.
Other research suggests that the 67 LR receptor is involved in the propagation
of prion diseases such as vCJD. This research may lead to treatments for diseases
like Mad Cow disease among others.10
For the latest information on tea research visit the Tea
Health Research web site.
3. Oolong. It is said that oolong
tea first began to be produced at Mt. Wu Yi Shan in Fujian Province at the
end of the Ming Dynasty about 400 years ago. The process of making Oolong
is somewhat more delicate and involved than other teas because it interrupts
the fermentation process at a subjective point.
Large mature leaves are dried on flat bamboo mats and withered in the sun
for less than an hour. Then the leaves are withered in the shade or at room
temperature for six to eight hours. Every hour the leaves are gently shaken
so that the leaf edges bruise. during this process the leaves lose 20% of
their moisture content and the leaf edges turn a reddish colour. When the
tea master determines that the right level of fermentation has been reached
the leaves are pan heated to halt the oxidation process. The leaves are then
rolled and re-fired and then cooled, rolled, and fired again.
Most Oolong tea is grown and produced in Taiwan and large quantities are consumed
there. Harder to find than green or black tea, the flavour of the tea can
vary depending on the many factors involved in making it. If a tea master
chooses to allow the leave to oxidize extensively a fruity flavor will result.
If the leaves are fired early or for a longer time, then a more nutty and
mellow flavor will be achieved.
4. Summary.
All tea has health benefits, so consider drinking a variety every day. The
more you drink, the more you will notice the subtle flavors of each different
type, and the more discerning will be your pallet. Green tea has been in the
lime light for several years due to its verified effect on health and well
being. Black and Oolong tea offer complimentary benefits and variety. Your
sense of taste and smell will guide you to quality. Learn to brew loose tea
leaves with the help of modern easy to use filters. Once you find the right
technique you will never go back to bagged tea again.
© Richard R. Powell
- August 2004
Notes:
1. Ascribe Health & Fitness News Service; 12/3/2003
2. Journal of Nutrition; Oct 2003, Vol. 133 Issue 10,
p3298
3. Archives of Internal Medicine; June 23, 2003
4. Cancer Weekly, 7/10/2001, p14
5. Quoted in American Fitness, Jan/Feb2004, Vol. 22 Issue
1, p31
6. Cancer Weekly - November 18, 2003 - Page 45
7. Natural Health; July 2003, Vol. 33 Issue 5, p19
8. Dermatology Times; April 2003, Vol. 24 Issue 4, p73
9. Nature Structural and Molecular Biology; DOI: 10.1038/nsmb
743
10. New Scientist; March 2004, Vol. 181 No 2439, pg19
