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GREEN TEA FREQUENTLY ASKED
QUESTIONS
1) What is tea?
Tea is a hot water infusion made from leaves of the
Camellia sinensis bush, a cousin of the flowering camellia. Green tea, black
tea, white tea and oolong tea all come from the Camellia sinensis bush
and are the only "true teas."
2) Is herbal tea also tea?
Tea made from herbs or anything other than the eaves of the Camellia sinensis
bush are not true tea, strictly speaking.
3) What's the difference between green tea, black
tea, oolong tea and white tea?
The way the Camellia
sinensis leaves are processed determines whether the tea is green, white,
black or oolong.
- For green tea - The leaves are plucked
then rushed to the processing plant where they are steamed or pan-fired
immediately to prevent them from fermenting. Unfermented leaves contain large
amounts of catechins, which are powerful disease fighters a potent
antioxidants.
- For white tea - White tea is the same
thing as green tea except that it's made up of only the bud and (sometimes)
the newest leaf or two. It contains even larger amounts of catechins than
regular green tea and is processed the same way.
- For black tea - The leaves are picked
then purposely crushed and left to wither for a day or two to encourage
fermentation. This changes the catechins into substances called thearubigens and theaflavins,
which have some health benefits but not nearly as many as the catechins.
- For oolong tea - The leaves are
crushed and left to wither, but for a shorter period of time than black tea.
This partial fermentation of the leaves converts some but not all catechins to
thearubigens and theaflavins.
4) What are catechins?
Catechins (pronounced CAT-i-kins) are
powerful antioxidants and potent disease fighters that are found primarily in
green tea. While you can find some catechins in black and oolong tea, wine,
ginkgo biloba leaves and pine bark, they're found in much larger quantities in
green tea. Weight-wise, catechins account for 15-30% of green tea, but only
8-20% of oolong tea and 3-10% of black tea.
Catechins are a sub-group of the
flavonoids, which give flowers and fruits their yellow, red and
blue colors and have vitamin-like activity. Both catechins and flavonoids belong
to a larger group called the polyphenols,
compounds that have strong antioxidant, anti-bacterial and anti-cancer activity.
5) What are the different types of catechins?
There are five types of catechins:
- gallocatechin (GC)
- epicatechin (EC)
- epigallocatechin (EGC)
- epicatechin gallate (ECg)
- epigallocatechin gallate (EGCg)
6) Are all catechins the same?
Although they're closely related chemically, the catechins
have slightly different properties and potencies. EGCg is believed to be the most
potent of the group.
7) What can the catechins do for your health?
Study after study has show that the catechins
(especially EGCg) can:
- lower total cholesterol
- lower LDL cholesterol
- increase HDL cholesterol
- fight atherosclerosis
- interfere with the cancer process at several stages
- destroy certain powerful bacteria (including
salmonella and cholera)
- assist in weight loss
- fight tooth decay
- act as an effective food and cosmetic preservative
Findings From Some Recent Studies on Green Tea
Scientists analyzing the eating and drinking habits of 1,000 Asian
women in Los Angeles found that those who drank green tea had a 43%
lower risk of getting breast cancer compared to those who drank no tea.
And the more tea they drank, the lower the risk.1
Test tube studies confirm that EGCg promotes the death of existing
melanoma cells (deadly skin cancer) while slowing the production of new
cells.2
In mice, green tea extract improves physical endurance, increases the
rate of fat-burning and decreases the concentration of lactic acid in
their blood.3
Green tea enhanced the survival time of women with ovarian
cancer. Scientists enrolled 254 women with epithelial ovarian cancer in
their study, then followed up three years later. Of those who habitually
drank green tea, 78% survived until the time of the interview, compared
to only 48% of the non-tea drinkers.4
Test-tube and animal studies have shown that green tea helps fight
Kaposi’s sarcoma (the rare form of cancer seen in AIDS patients) by
inhibiting the growth of cancer cells and prompting existing cancer cells
to "commit suicide."5
In lab animals, the antioxidant effects of green tea diminished
calcification and, as a result, inhibited the formation of kidney
stones.6
A study of 1,900 people who had had heart attacks found that four
years after the attack those who consumed tea (green or black) in moderate amounts
(about 2 cups a day) had a 28% lower death rate than those who drank no
tea. And those who drank more than 2 cups a day had a 44% lower death
rate.7
8) How many catechins are in a cup of green tea?
The average 6-ounce cup of green tea contains
between 50 and 100 mg
catechins.
9) How much green tea
do you need each day to get the health benefits?
Most studies have concluded that you
need 3-10 cups of green tea per day, or up to 1,000 mg. of catechins.
10) What other helpful substances are in green tea?
Green tea also contains:
- flavonols, which combat free radicals.
- vitamin C, needed to keep the immune system strong
- various
B vitamins that help the body metabolize carbohydrates,
manufacture fatty acids and amino acids.
- vitamin E, a powerful antioxidants.
- fluoride, which strengthens tooth enamel
11) What's the difference between green tea and green
tea extract?
To make green tea extract, the catechins (most
often EGCg) are isolated and drawn out, using water or steam, then condensed
before spray drying. The resulting powder can be put into a tablet or capsule or
made into a liquid. Green tea extract contains many times more catechins than
could be found in a cup of green tea and is swallowed in pill form or added to a
drink.
12) Did the FDA say that green tea had no health
benefits?
No, the FDA simply said that in their opinion
there was not enough scientific evidence available to allow food manufacturers
to make health claims regarding green tea's actions against cancer or heart disease.
13) Have the benefits been demonstrated in
scientific studies?
Yes, there are literally hundreds of studies
performed by top scientists at leading universities and research centers that
show that green tea promotes good health in many, many ways. These studies have
been published in prestigious medical journals including the American Journal
of Clinical Nutrition, Archives of Internal Medicine, the British
Medical Journal and the Lancet.
Footnotes:
1 Wu AH, Yu MC, Tseng CC, et al. Green
tea and risk of breast cancer in Asian Americans. International Journal of Cancer
2003;106(4): 574-9.
2 Nihal M, Ahmad N, Mukhtar H, Wood GS. Anti-proliferative and proapoptotic
effects of (-)-epigallocatchin-3-gallate on human melanoma: possible
implications for the chemoprevention of melanoma. International Journal of
Cancer 2005;114(4):513-21.
3 Murase
T, Haramizu S Shimotoyodome A, et al. Green tea extract mproves
running endurance in mice by stimulating lipid utilization during
exercise. Am J Physiol Regul Integ Comp Physiol, 2006;290(6):R1150-6.
4 Zhang
M, Lee AH, Binns CW, Xie X. Green tea consumption enhances survival of
epithelial ovarian cancer. Int J Cancer, 2004;112(3):465-69.
5 Fassina
G, Vene R, Morini M, et al. Mechanisms of inhibition of tumor
angiogenesis and vascular tumor growth by epigallocatechin-3-gallate. Clin Cancer Res, 2004;10(14):4865-73.
6 Itoh
Y, Yasui T, Okada A, et al. Preventive effects of green tea on renal
stone formation and the role of oxidative stress in nephrolithiasis.
J Urol 2005;173(1):271-75.
7 Mukamal
KJ, Maclure M, Muller JE, et al. Tea consumption and mortality after
acute myocardial infarction. Circulation, 2002;105(21):2476-81.
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Nadine Taylor, M.S., R.D. presents
GreenTeaLibrary.com,
the most comprehensive collection of scientific information
describing the health benefits of green tea.
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