| Tea's Role in Cancer Risk Reduction |
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Preliminary research suggests that the flavonoids in tea could play a role in
human cancer risk reduction possibly by combating free radical damage,
inhibiting uncontrolled cell growth (cell proliferation), by promoting
programmed cell death (apoptosis) and boosting the immune system to help
fend off the development and promotion of cancer cells. Leading scientists
worldwide are actively studying these potential mechanisms and clinical trials
and population studies are underway. More evidence is needed before any
definitive conclusions can be drawn. Recent findings include:
DNA Damage
* A recent study found that smokers who drank four cups of decaffeinated
Green Tea per day demonstrated a 31 percent decrease in biomarkers of
oxidative DNA damage in white blood cells compared to those who drank four
cups of water. Oxidative DNA damage is implicated in the development of
various forms of cancer.
*Epigallocatechin gallate (EGCG) may protect normal cells from cancer-causing
hazards as well eliminate cancer cells through apoptosis. Researchers tested the
potential anti-cancer benefits of Green Tea polyphenol, EGCG, in hamster cells
and discovered that EGCG suppressed DNA changes and damage from
carcinogens. EGCG also protected from further damage from the carcinogens
and inhibited growth and multiplication of cancer cells.
* An animal study identified beneficial changes in immune function after Black
Tea ingestion in cancer-bearing animal. Black Tea beneficially altered immune
responses that helped protect immune cells against harmful cancerous cells. The
study found Black Tea acted like anti-cancer drugs that help boost the immune
system without promoting the proliferation of cancerous cells.
Digestive Cancers
*An epidemiological study conducted by the University of North Carolina found
consumption of the equivalent of 2.5 cups of tea per day or more was
associated with a 60 percent drop in rectal cancer risk among Russian women
from Moscow, as compared to women who drank relatively less than 1.2 cups of
tea per day. Those women who drank approximately 1.2 to 2.5 cups of tea per
day had a 52 percent reduction in the risk of rectal cancer.
*Based on data from the NHANES I Follow-up study (NHEFS), researchers found
that tea drinkers had about a 42 percent reduced risk of colon cancer as
compared to non-tea drinkers. Men who drank more than 1.5 cups of tea per
day were found to have a 70 percent lower colon cancer risk.
* Researchers who followed a group of over 34,000 post menopausal women
between 55-69 years of age for 12 years found that those consuming high levels
of catechins experienced up to a 45 percent decrease in the instances of rectal
cancer. Catechins are a class of flavonoids found in tea, fruits and vegetables.
Catechins derived from tea were most strongly linked to a decrease in rectal
cancer.
*The Iowa Women's Study, which followed post-menopausal women between
the ages off 55 and 69 for eight years, found that participants who drank two or
more cups of tea per day had a 32 and 60 percent reduced risk of developing
digestive and urinary tract cancers, respectively.
A study conducted with members of the Shanghai Cohort (18,244 men aged
45-64 years at recruitment with up to 12 years of follow-up) discovered a
statistically inverse relationship between positive tea polyphenol levels (as
measured in urine) and gastric cancer.
*A large population-based case-control study found an inverse relationship
between Green Tea consumption and the risk of colon, rectal and pancreatic
cancer. Male participants, who drank the equivalent of 4.5 servings of tea per
day, had an 18 percent decrease in colon cancer risk and 28 percent decrease
risk of rectal cancer. Female participants, who drank 3 servings of tea per day,
were observed to have a decreased risk of colon and rectal cancer by 33 percent
and 43 percent, respectively. Risk of pancreatic cancer was also reduced in both
men and women by 37 percent and 47 percent respectively.
*Researchers examined whether a combination of two compounds known to
exhibit anti-cancer activity, Green Tea polyphenol, EGCG, and sunlindac
(a non-steroidal anti-inflammatory drug), would work synergistically to prevent
colon cancer carcinogenesis in rats. Findings suggested that EGCG and sulidac
worked together to suppress pre-cancerous lesion formation by enahncing
programmed cell death, or apoptosis.
*Researchers sought to investigate the effect of Black Tea polyphenols (BTP) on
induced DNA damage to colon mucosa is prevented by consumption of Black
Tea polyphenols.
* Major compounds of Green and Black Tea, EGCG and theaflavins respectively,
are known to inhibit proteins which are closely associated with tumor growth
and metastasis. These polyphenols exhibited apoptosis-inducing activity for
human colon caner cell lines.
*Researchers in Taiwan discovered a link between EGCG and cancer risk
reduction. The researchers found that the Green Tea polyphenol inhibited
proliferation of the caner cells by inducing cell death and blocking cell cycle
progression.
Skin Cancer
According to a study conducted by the University of Arizona, participants who
drank iced Black Tea and citrus peel had a 42 percent reduced risk of skin cancer.
*Hot Black Tea consumption is associated with a significantly lower risk of
squamous cell carcinoma (SCC), a form of skin cancer; tea concentration
(strength), brewing time and temperature all influence the potential protective
effects of hot Black Tea on SCC.
*Oral consumption of Green or Black Tea decreased the number of tumors in
mice following exposure to UV radiation.
*Green Tea polyphenols may have cancer preventive potential, especially in the
case of solar UV-induced cancer.
*Research suggests that compounds in Green Tea may protect skin from
ultraviolet (UV) radiation-induced damage when applied topically.
*Topical treatment of Green Tea polyphenols on human skin prior to UV
exposure inhibited indicators of DNA damage, thus inhibiting
phtocarcinogenesis, or UV-induced skin cancer.
*Experiments that show that administration of Green Tea, Black Tea or specific
flavonoids in tea inhibited the growth of established nonmalignant and
malignant skin tumors in tumor-bearing mice. In addition, oral administration of
Black Tea inhibited DNA synthesis and enhanced cell death (apoptosis) in both
nonmalignant and malignant tumors in tumor-bearing mice.
Oral Cancers
*A human intervention trial examined the effect of treating superficial
precancerous lesions (leukoplakia) in the mucosal lining of the mouth with a
mixed tea product. After the six-month trial, partial regression of the lesions was
observed in 37.9 percent of the group treated with tea as compared to only 10
percent of those treated with a placebo.
*Researchers examined the effects of tea and curcumin, a spice and
food-coloring agent, on oral cancer in hamsters. Hamsters were treated with a
cancer-causing solution topically inside the cheek three times a week for six
weeks. Two days after the last treatment of the solution, the hamsters were
given Green Tea as drinking fluid or curcumin applied topically three times per
week, the combination of Green Tea and curcumin treatment, or no treatment
for 18 weeks. At the end of this period, the scientists observed that the
combination of tea and curcumin, tea alone and in combination with curcumin
increased cancer cell death, or apoptosis.
Lung Cancer
* Studies comparing groups of mice treated with a tobacco-specific carinogen
and receiving either water or water enriched with tea-derived antioxidants
found that the tea-fed mice developed 24 percent fewer lung tumors and the
average size of the tumors was 38 percent smaller as compared to the water-fed
mice.
*Tea catechins were evaluated for their effects on cell proliferation, apoptosis
and associated gene expression in highly metastatic human lung cancer cells.
A significant reduction in cell proliferation after exposure to tea catechins was
noted. It is suggested that tea compounds can influence genetic alteration to
reduce the grown and survival of human lung cancer cells.
Tea's Role in Cancer Risk Reduction Page 2