Tea
Tea's
history is nearly 5,000 years old. Legend has it that it was discovered
in 2737 B.C. by a Chinese emperor when some tea leaves accidentally blew
into a pot of boiling water. In the 1600s tea became popular throughout
Europe and the American colonies. In 1908, Thomas Sullivan of New York developed
the concept of tea in a bag.
Kinds of Tea
Tea can be broken down in to 2 categories:
non-herbal teas and herbal teas. Non-herbal tea can be further
broken down into three basic categories: black, green and oolong. Black
tea is the most popular, being consumed by over 90 percent of the tea consumed
in U.S. Black tea has been fully oxidized or fermented and yields a
hearty-flavored, amber brew. Some of the popular black teas include English
Breakfast (a popular choice for breakfast due to its hearty flavor that
mixes well with milk), Darjeeling (a blend of Himalayan teas with a flowery
bouquet suited for lunch and snacks) and Orange Pekoe (a blend of Ceylon
teas that is the most widely used of the tea blends).
Green tea, unlike black tea, is not oxidized. It has a more delicate
taste and is light green/golden in color. Green tea, a staple in the Japan,
is gaining popularity in the U.S. due in part to recent scientific studies
linking green tea drinking with reduced cancer risk.
Oolong tea, popular in China, is partly oxidized and is a cross between
black and green tea in color and taste.
All regular non-herbal teas contain varying
amounts of antioxidants and caffeine.
While flavored teas evolve from these three basic teas, herbal
teas contain no true tea leaves. Herbal and "medicinal" teas are
created from the flowers, berries, peels, seeds, leaves and roots of many
different plants. Detox herbal teas are special teas made from a blend of
herbs with special detoxification and cleansing properties. These two do
not contain any caffeine. They are best for our body.
Benefits
of Tea
Non-herbal Tea is rich in antioxidant
polyphenols (catechins, flavonols, theaflavins and thearubigins).
These antioxidants are believed to be the
active ingredients behind the beneficial effects of tea. Antioxidants
help repair damage to cells and blood vessel walls from free radicals. They
also help reduce blood clots which could lessen the risk of a heart attack.
Flavonoids are also found in varying amounts of fruits and vegetables as
well.
While drinking non-herbal tea has been
promoted to cure everything from cancer to reduced heart attack, scientific
studies are not conclusive.
Experts at King's College, London studied 340 men and women who had suffered
heart attacks and matched them by age, gender and neighborhood residence
with people who had no history of heart attacks. They then compared the
two groups' coffee and tea drinking habits for a year. The tea drinkers
drank black tea as opposed to green tea (which contains fewer flavonoids)
or herbal teas (which contain none).
Findings revealed that the tea drinkers' risk of a heart attack approached
half of the non-tea drinkers. Scientists speculate that tea's beneficial
cardio effects are due to the beverage's large amounts of flavonoids.
Two cups of tea also have the equivalent antioxidant activity of one
and a half glasses of red wine, 12 glasses of white wine, seven glasses
of orange juice and 12 glasses of beer.
Tea consumption tended to reduce the development of aortic atherosclerosis
in rabbits when studied in a laboratory setting. Tea polyphenols exert marked
effects on cells, and inhibit neutrophil migration and inflammatory responses,
sometimes at low concentrations. Other studies have shown no significant
difference. Unfortunately epidemiological evidence relating regular
consumption of tea or related polyphenols to cardiovascular heart disease
is equivocal. Specifically, catechins are absorbed from tea, but low plasma
concentrations are attained and whether such low plasma level have therapeutic
effect remains to be validated. Also, the bioavailability of theaflavins
and thearubigins is unknown at this time. Tea does not reduce blood pressure
or plasma lipids in well-controlled human trials, although sporadic case
reports have been positive. Tea polyphenols inhibit LDL lipid peroxidation
in vitro, but the effect ex vivo is small.
Antioxidant
Content of Tea
The antioxidant content of various types of tea has been well studied. An
analysis on 20 common brands of tea has shown that they contain widely varying
amounts of antioxidants, which are known to help fight off cancer and heart
disease among other illnesses.
The following teas were brewed for 3 minutes each and the antioxidant
level is shown below:
Brand of Tea | Catechin content (in milligrams) |
Celestial Seasonings Green Tea | 217 |
Lipton Green Tea | 201 |
Bigelow Darjeeling Blend (black tea) | 164 |
Uncle Lee's Green Tea | 157 |
Stash Premium Green Tea Decaf | 53 |
Twinings Earl Grey Black Tea | 46 |
Bigelow Constant Comment (black tea) | 38 |
Bigelow Constant Comment Decaf | 10 |
Lipton Lemon Iced Tea | 0 |
Snapple Peach Iced Tea | 0 |
The overwhelming of all tea consumed in the U.S. is
black tea. The processing method of tea may account for some of the differences
in antioxidant levels. Green tea is commonly thought to have more antioxidants
than black tea. This was often, but not always
the case. Most scientists that have really studied this have
found that the number of antioxidants in black tea is actually higher than
what is found in green tea.
Tea
and Caffeine
Caffeine
was first discovered in tea in 1827, and was named theine. It was later
found in mate and various other plants. Eventually it was shown that the
theine of tea was identical with the caffeine of coffee, and the term theine
was then dropped.
Caffeine is the most widely used drug
in the world today. Found in beverages like coffee, tea and soft drinks,
it is consumed by 8 out of 10 adults in the Western world today. Its toxic
effect is without doubt.
In the study, a group of 10 healthy volunteers were given either inactive
placebo capsules or capsules containing 100 milligrams of caffeine--a quantity
equivalent to one cup of coffee or 2-3 cups of tea. The volunteers were
then given the opposite capsule from the previous dosage on another day.
The results showed that caffeine consumption caused an increase in wave
reflection -- a measure of arterial stiffness -- for at least 2 hours.
Just one cup of coffee or two cups of
tea is enough to harden a person's arteries for several hours afterwards.
This puts extra pressure on the heart, thus increasing the risk
of heart attack or stroke. The same amount of caffeine can raise the blood
pressure by 5 to 10 millimeters of mercury. If this increase is on a regular
basis, it could have negative repercussions on a person's long-term prognosis.
It is evident today that many of our cancers are related to a dominance
of estrogen. In a world flooded with estrogen and estrogen-like compounds,
it is important for our body to have as low an estrogen load as possible.
Studies have shown that drinking more
than two cups of coffee (400 mg of caffeine) a day may increase estrogen
levels in women. It could also lead to problems such as endometriosis and
breast pain.
Having high levels of estrogen for women in such cases can be detrimental
as it can lead to breast cancer in women and prostate cancer in men. Those
who have a family history of cancer also have a higher risk.
In a clinical trial conducted, about 500 women between the ages of 36 to
45 were studied. These women were not pregnant, not breast-feeding or having
hormonal treatment. They were interviewed regarding their diets, smoking
habits, height and weight. Their hormone levels during the first five days
of their menstrual cycle was also measured.
The results showed that women who consumed more than one cup of coffee (
or two cups of tea) a day had significantly higher levels of estrogen during
the early follicular phase of their menstrual cycle.
Those who consumed at least 500 mg of caffeine daily, the equivalent of
four or five cups of coffee (or 10 cups of tea in caffeine equivalent) had
nearly 70% more estrogen than women who consumed less than 100 mg of caffeine
daily.
Caffeine intake from all sources was associated with higher estrogen levels regardless of the women's age, body mass index (BMI), caloric intake,
smoking habits, alcohol and cholesterol intake. Caffeine consumption
increases estradiol levels. There are three different forms of estrogen
in the body - estrone, estradiol, and estriol. Estradiol is the form that
is pro-cancerous. Women should limit their intake of coffee to not more
than one to two cups daily to decrease their risk of having more serious
health problems.
Chronic high caffeine intake can also
lead to adrenal gland exhaustion and the reduction of production of progesterone.
The proper progesterone to estrogen ratio is therefore not maintained, resulting
in further estrogen dominance.
In summary, chronic long term caffeine
consumption from non-herbal tea can lead to increased cardiac stimulation,
estrogen dominance, and adrenal gland exhaustion.
Additional
Facts on Caffeine
Decaffeinated tea is not caffeine free. It still contains up to .4% by
dry weight caffeine content.
The longer the tea leaves have fermented, the greater their caffeine content.
The shorter the brewing time, the less caffeine ends up in the cup.
The smaller the tea leaf, the stronger the extraction of caffeine.
The first and second leaves of the tea plant are believed to contain the
largest amount of caffeine at 3.4 %.
How
much caffeine is in Tea?
Other
than herbal tea such as chamomile tea, all non-herbal tea contain caffeine,
though less than coffee.
The amounts of caffeine in any single serving of these beverages vary significantly.
The amount of caffeine in coffee or tea depends on a number of factors,
including the variety of coffee bean or tea leaf, where it is grown, particle
size used, (the particular coffee "grind" or tea leaf cut), and
the method and length of brewing or steeping. Also with tea, studies show
that leaf location on the tea plant, affects content of caffeine in that
leaf.
On the average, coffee contains the most
caffeine, and tea provides only 1/2 to 1/3 as much. One of the
more confusing aspects of caffeine content is the fact that coffee contains
less caffeine than tea when measured in its dry form. The caffeine content
of a prepared cup of coffee is significantly higher than the caffeine content
of a prepared cup of tea.
The length of the infusion in water also
affects caffeine content. Black tea infused for 5 minutes yields 40-100
milligrams, whereas a 3-minute infusion produces 20-40 milligrams, or half
as much.
Caffeine
Content Comparison
Caffeine Content Comparisons | ||
The following
is the approximate caffeine content of various beverages |
Milligrams of Caffeine | |
Item | Average
per serving |
Range |
Coffee (5 oz. cup) | 90 | 40 - 170 |
Cola (12 oz. can) | 45 | 30 - 60 |
Black Tea (one tea bag) | 40 | 25 - 110 |
Oolong Tea (one tea bag in 8 oz) | 30 | 15 - 55 |
Green Tea (one tea bag in 8 oz) | 20 | 10 - 30 |
Decaf Coffee | 5 | 3-10 |
Decaf Tea (one tea bag in 8 oz) | 2 | 1 - 4 |
Herbal Tea (one tea bag in 8 oz) | 0 | 0 |
Decaffeinated tea
may be the way to go if you have to drink non-herbal tea. There
are 2 usual ways to decaffeinate tea, the more common one utilizing a chemical
called ethyl acetate. This process, however, also diminishes the healthy
effects of the tea by eliminating up to 70% of the polyphenols found in
the tea. The other method of decaffeinating is by using carbon dioxide and
water. This will retain about 95% of the healthy substances.
How
do I know if I can tolerate the caffeine in Tea?
Caffeine tolerance varies greatly among
individuals. Any natural compound, when taken in excess, can
be toxic. Studies have shown a possibility that caffeine can interfere with
fetal development, including lowering birth weight and contributing to skeletal
and other abnormalities. Until they reach the age of seven or eight months,
babies cannot get rid of caffeine metabolites, and traces of caffeine can
appear in breast milk as well. Pregnant or nursing mothers should refrain
from any caffeinated beverage, including tea (other than herbal tea).
For normal adults, your body will tell you if you listen carefully. Some
people find it hard to fall asleep
after drinking tea. Others may have palpitations
or fast heart rate. Others may have sweaty
palms. The individual reaction may vary. The stimulatory
effect of tea can last for up to 36 hours in highly sensitive individuals,
although the norm is somewhere between 2-8 hours.
Green
Tea - As Good as It Sounds?
Hundreds
of research studies over the past decade shows health enhancing effect of
green tea - from cancer prevention to reduction in blood pressure. Widespread
marketing and promotional campaign has made green tea a household word.
Key ingredients for these benefits appear to be the polyphenols found in
green tea that have strong antioxidant properties.
Experts at the University of Kansas have proclaimed that green tea is equal
to 100 times of the antioxidant strength of Vitamin C and 25 times that
of Vitamin E. A USDA study found that the antioxidant strength of green
tea is better than that of 22 fruits and vegetables. The USDA Human Nutrition
Research Center on Aging discovered that one cup of green tea brewed for
up to three to five minutes contains about the same amount of antioxidants
as one serving of vegetables.
The antioxidants in green tea help prevent
or delay damage to body cells and tissues. They also reduce the risk of
heart attack and protect blood vessels that feed the heart and brain. Green
tea also appears to speed up calorie burning including fat-calorie burning.
Green
Tea May Prevent Cancer
Green tea could prevent cancer due to its special ingredient, epigallocatechin
gallate, which is found mainly in (670 g/kg) in green tea extract, in addition
to the cateclins with antioxidant properties. To explore this claim, scientists
treated cells grown with or without green tea extract with iron as an oxidative
stimulus for two hours. Supplementation with green tea extract significantly
decreased malondialdehyde production and DNA damage after iron oxidative
treatment. Malondialdehyde is a lipid peroxidative product, which is believed
to be a marker of radical generation and tissue damage. There was no effect
on membrane distribution of n-3 fatty acids due to iron treatment in cells
that were not treated with green tea
Research has revealed that nearly all tea components strongly inhibit adduct
formation with human DNA, as well as artificially induced free radicals.
Beneficial enzyme such as glutathione-S-transferase is enhanced by nearly
all tea components.
Green tea main components (hot aqueous, polyphenols, epicatechin, epicatechin
gallate, epigallocatechin gallate) and black tea extracts (hot aqueous,
polyphenols and theaflavins) also also been shown to strongly inhibited
tumour transformation in rodent breast tissue cultures and epithelial cells
as well as human lung epithelial cells in laboratory studieds. Ornithine
decarboxylase activity (involved in the synthesis of urea, an end product
of protein metabolism) was suppressed by nearly all the green tea extracts
but none from black tea.
Hence the results show that black and
green tea extracts helped reduce genetic mutation, anti-proliferation and
anti-cancer incidences.
Green
Tea Good for Brain
Chemicals found in green tea and other plants may prevent the brain damage
that occurs after strokes and other brain injuries, say researchers from
the University of California, San Francisco (UCSF). Researchers tested the
effects in the laboratory of two plant-derived chemicals on brain cells
under stress - gallotannin and nobotanin B. Gallotannin is found in green
tea and other plants. Nobotanin B, a similar chemical, comes from the Brazilian
glory bush. Both chemicals block PARG activity. Both gallotannin and nobotanin
B also block brain cell death from chemicals that normally overly stimulate
the cells.
The PARP/PARG system is activated by the release of cell-damaging oxygen
radicals, a phenomenon called oxidative stress, and when cells become overexcited
by various toxins. Blockers of PARP activity have already been used to prevent
brain cell death but as PARG blockers, gallotannin and nobotanin B were
10 to 1,000 times more potent in preventing brain cell death caused by oxygen
radicals. Gallotannin was 100 times more effective than antioxidants, which
are chemicals that can soak up the toxic oxygen molecules.
Green
Tea - Drink Only If You Have To
While numerous studies continue to show green tea's anti carcinogenic effect, intake of more than 1 cup a day is not
warranted because there are simply many better ways to get the antioxidant
from sources other than green tea without the caffeine. For example,
Vitamin C and E are strong antioxidants that can be easily obtained from
whole fruits and vegetables. Green tea is the best of all non-herbal tea.
Unfortunately, it also contains caffeine and there is no apparent escape
from this toxin. Caffeine is a stimulant and is not recommended for those
with cardiovascular disease, adrenal compromised conditions.
It is unlikely that moderate consumption
of green tea (one cup a day) will have any negative effect if the body is
in optimum condition. Over indulgence should be avoided.
Herbal
Tea
Herbs are found mainly in the form of teas, powders or extracts. Herbal
teas can be made and consumed readily throughout the day, as they are
mild and gentle. In contrast to non-herbal tea such as black or green tea,
they contain no caffeine and are excellent
detoxification tools and digestive aids. Herbal ingredients and
commonly used ingredients that enhance intestinal motility include:
senna leaf, peppermint leaf, stevia leaf, buckthorn bark, damiana leaf,
RED peel, chamomile flower, and uva ursi leaf.
Detox
Herbal Tea
This is a special group herbal tea that
uses a blend of herbal tea and natural compounds that help with the digestive
system, promote bowl movement, enhance weight loss, and detoxify the body.
They are available in tea bags or raw tea that can be brewed.
Detox tea are best taken after the evening
meal. (It is always good to eat your regular meal fortified with
digestive enzymes to enhance breakdown of food in the gastro intestinal
tract as a routine practice). Bear in mind that detox teas usually have
a laxative effect. Start slowly if you are new to detox teas. You should
begin by steeping the tea just 2 minutes (in 1-2 cups of water) for the
first 3-5 days. As your system adjusts, you may increase steeping to 5 minutes.
Most individuals will experience increased bowel movements or slight cramping
sensation during the first few days. This is due to the initial cleansing
of the body system and is normal.
A
good detox tea will help produce a good bowl movement that is soft, smooth,
and easy to pass, but not watery.
It is not uncommon, however, to have experience of watery stool, especially
during the initial cleansing process.
It should be noted that the consistency of the bowl movement varies greatly
depending on the person. Adjust the amount of herbal tea you need to achieve
the desired result. Suffice to say that the bowl movement should not
be too watery on an on going basis, which can lead to dehydration and electrolyte
imbalance if one is not careful. It is always a good habit to drink more
water than normal during a detoxification and cleansing state.
Tea
Tips:
Drink only herbal teas that contain
no caffeine for general well-being.
Drink detox herbal tea after meals and
during the day for detoxification and weight reduction.
If you have to drink regular non-herbal
tea, green tea is the best. One cup a day should pose no negative
effect.
The temperature of the tea does not matter.
Tea, whether cold or hot, contains the same polyphenols and caffeine. (Polyphenols
are a class of flavonoids that function as powerful antioxidants.) Iced
tea is more dilute than hot tea; therefore the same amount of iced tea may
contain less antioxidants than hot tea.
Avoid Ready-to-drink tea. It
would be nice if you could the gain the health benefits of green tea in
a ready-to-drink beverage, but the only truly healthy option is to brew
your own. The problem with ready-to-drink, processed teas is that they tend
to be high in calories and sugar. The companies that produce them have found
a good tagline -- that green tea is good for you - and to make it more pleasing
to the taste buds, they have loaded it with sugar or artificial sweeteners.
Check the food label and avoid drinks or foods that contain high-fructose
corn syrup. Although when in its natural state, which is in fruits, fructose
is fine, high- fructose corn syrup will dramatically increase the blood
sugar level when broken down in the body. This will, in turn, raise the
insulin levels, which can lead to insulin resistance in the long run. For
people who do not fancy the taste of traditional green tea, one variation
is to steep it with ginger or mix it with ginger tea and some honey.
Conclusion
Tea comes in many varieties. Common tea such as black tea contains little
antioxidant and about 1/3 the amount of caffeine compared to coffee. Green
tea has about 1/5 to 1/3 the caffeine content, but contains a good amount
of antioxidants. Decaf tea also contains caffeine, although much less than
regular tea and also less than decaf coffee. Caffeine is a known stimulant
and a pro-aging compound. The negative effect of caffeine in tea outweighs
any health benefits. While researchers continue to point to the cancer prevention
effect of tea, we continue to caution the fact that for cancer prevention,
there are better ways. Non-herbal tea contains caffeine, which we
all know are potent stimulants and can, and do, upset the autonomous nervous
system. For anti-cancer properties of tea, you should consider taking antioxidants
from whole foods and supplement with nutritional factors like grape seed
extract. There are many other ways to obtain antioxidants other than from
non-herbal tea. Herbal tea is an exception because it
does not contain caffeine. Detox herbal tea should be taken regularly to
detoxify and tonify the body.
Anyone with high blood pressure or weak cardiovascular system should
avoid caffeine, which rules out both green and black tea. Other than
herbal tea and herbal detox tea, both of which contain no caffeine, the
only other liquid to be consumed is pure filtered water. Another option,
however, is to purchase the decaffeinated varieties of tea. Even so, it
is to be noted that even decaf tea contains up to 2.5% of caffeine, about
half of what can be found in regular tea.
© 2006 Michael Lam, M.D. All Rights Reserved.