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Tea to Combat Cancer: Good News Comes in Threes
1/16/2006
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1) Green tea may reduce breast cancer risk; 2) Black tea may cut risk of ovarian cancer; 3) Research reveals more anti-cancer effects from tea

by Craig Weatherby



It’s clear that tea is a very healthful drink. Thanks to their polyphenol antioxidants, all three types of tea—white, green, and black—confer impressive preventive health benefits with regard to America’s epidemic of obesity and its two top killers: cardiovascular disease and cancer.

Tea enhances cardiovascular health in many ways: it lowers blood cholesterol and pressure, blocks oxidation of LDL cholesterol, reduces unhealthful blood stickiness and clotting, improves endothelial (blood vessel wall) function, and inhibits vascular inflammation.


And the new research results described below strengthen the case that tea cuts the risk of cancer.


Tea versus cancer: new findings build on ample prior evidence

The introduction of our new Vital Choice Organic Teas prompted us to take a closer look at the state of the evidence that tea can help prevent or hinder cancer.

Coincidentally, several new reports landed in our inbox, bringing to our attention research results that appear to expand the already considerable anti-cancer potential of tea.


Tea displays strong anti-cancer properties in cell-culture and animal tests, where it protects against artificially induced cancers of the stomach, lung, esophagus, duodenum, pancreas, liver, breast, and colon. And most epidemiological (population) studies link regular consumption of tea—especially green tea—with reduced rates of certain common cancers.

The anti-cancer potential of green tea was first uncovered by population studies in Japan, whose results indicated that drinking ample amounts—about five 4-oz cups or three 6-oz cups a day—might cut the average green tea consumers’ overall risk of cancer.

White tea is not as well studied for cancer prevention, but it contains even more of the catechin-class polyphenol antioxidants that give green tea its anti-cancer powers.  Black tea contains a different mix of antioxidants but still appears to offer substantial cancer-blocking benefits.


1) Green tea reduces breast cancer risk, according to two U.S. studies

The results of two recent studies offer strong evidence that green tea can help prevent breast cancer.


2003 USC report

Three years ago, researchers at the University of Southern California’s Keck School of Medicine published the results of a “case-control” study of breast cancer conducted among Chinese, Japanese and Filipino women in Los Angeles County.


The scientists interviewed 501 breast cancer patients and 594 “control” subjects without breast cancer, collecting detailed information on menstrual and reproductive factors; dietary habits—including intake of black and green tea—and other lifestyle factors.


They found that while regular consumption of black tea did not raise or reduce the risk of breast cancer, drinking green tea reduced risk of breast cancer significantly.  Crucially, this apparent advantage persisted after adjusting for possible confounding factors such as the participants’ age, Asian ethnicity, birthplace, age at onset of menstruation, menopausal status, use of menopausal hormones, body size and intake of total calories and black tea.


The data revealed the risk or breast cancer declined significantly risk as green tea intake increased. This significant inverse association between risk of breast cancer and green tea intake remained after the researchers made further adjustments to account for other potential results confounders, including smoking, alcohol and coffee intake, family history of breast cancer; physical activity, and intake of soy and dark green vegetables.


As the team concluded, regular consumption of either green tea or soy foods both appeared to reduce the risk of breast cancer, independently: “While both green tea and soy intake had significant, independent protective effects on breast cancer risk, the benefit of green tea was primarily observed among subjects who were low soy consumers.”


2005 University of Minnesota report

Last November, a research team at the University of Minnesota’s Cancer Center published their statistical analysis of all of the 13 extant research studies whose data sets included participants’ level of green or black tea consumption and health status, including diagnoses of breast cancer.


This type of investigation—called a meta-analysis—is considered the most reliable kind of scientific study, since it pools the results of all relevant studies.


Their findings with regard to green tea were very positive, if unsurprising, given the strong beneficial effects seen in cell and animal studies of the effects of green tea’s antioxidant polyphenols on cancer initiation and growth:


“For green tea, the combined results from the four studies indicated a reduced risk of breast cancer for highest versus non/lowest intake… The results of this meta-analysis indicate a lower risk for breast cancer with green tea consumption…”


Their findings on black tea were not as clear, since some studies showed a preventive effect while others did not.


FDA label-claim ruling appears obsolete on arrival

Unfortunately, the U.S. Food and Drug Administration (FDA) issued its ruling on tea marketers’ petition to allow an anti-cancer health claim on tea labels last June, before publication of the landmark meta-analysis from the University of Minnesota team.


The label claim language FDA issued—which says that it is “highly unlikely” that green tea reduces the risk of breast or prostate cancer —is worse than useless, since it appears highly biased and inaccurate, and would only discourage consumers from using tea to combat cancer, despite the large body of evidence—including the two U.S. studies described above—whose results indicate that tea inhibits cancers in many ways.


We suggest that FDA reexamine the issue immediately, in light of the positive outcomes of the USC study and especially in light of the University of Minnesota team’s landmark meta-analysis.


2) Black tea may reduce risk of ovarian cancer

Every year, more than 20,000 American women are diagnosed with ovarian cancer, which means that the average American woman faces about a 1-in-58 chance of developing the disease.  Ovarian cancer is hard to detect early because its symptoms—e.g., abdominal bloating, indigestion and urinary urgency—resemble those of less serious conditions.


According the results of a newly-published Swedish study, drinking two cups of tea daily may cut women’s risk of ovarian cancer. The Scandinavian researchers tracked 61,057 women for an average of 15 years, and gathered information about their daily diets.


About two percent (301) of the women developed ovarian cancer during the study, and those who reported drinking two or more cups of tea a day were 46 percent less likely to develop the disease than women who drank no tea. Drinking less than two cups of tea daily also reduced the risk of ovarian cancer, but to a lesser degree.


Most of the tea drinkers were imbibing black tea. Unlike the phenols in green and white tea—known as catechins—the dominant polyphenol antioxidants in black tea are theaflavins.  These closely related polyphenols get created when the oxidation that turns green tea leaves black also converts 70 to 90 percent of their catechins to theaflavins and other phenolic compounds (e.g., thearubigens and bisflavanols).


More research is needed to confirm these findings, since similar population studies have produced conflicting results. And, women who drink tea might simply have healthier lifestyles than non-tea drinkers.


3) New findings reveal more of tea’s anti-cancer secrets

Tests in cell cultures and animals have long since proven that tea can strongly inhibit the formation or growth of malignant tumors, but it’s been unclear how it does this.


New research results published during the last two years has further lifted the fog surrounding tea’s anti-cancer effects.


The flavon-3-ol polyphenol antioxidants in tea—especially epigallo-catechin-gallate (EGCG)— inhibit tumors in several ways:

  • Inhibit a number of tumor cell proliferation- and survival-related proteins.
  • Inhibit processes and compounds essential for tumor growth, metastasis, and invasion of organs (e.g., angiogenesis and key proteases).
  • Block the activity of specific cell receptors called tyrosine kinases, and related cell-signaling pathways (i.e., signal-transduction paths).
  • Inhibit the activity of two “genetic switches” made famous in the bestselling anti-aging books by Dr. Nicholas Perricone (AP-1 and NF-kappaB). This has the effect of inhibiting excessive cell proliferation, which is a key factor in creation of cancers.
  • Promote the “suicide” of cells beginning to turn cancerous: a process known as apoptosis.

Now, thanks to research results published in 2004 and 2005, it appears that green tea may protect against cancer in three additional ways:

  • In late 2005, University of Rochester researchers published their discovery that the key anti-cancer polyphenol in green tea—epigallo-catechin-gallate or EGCG—binds to a protein called HSP90, which is found at higher levels in cancer cells than in healthy cells, and which drug companies have been targeting. This binding effect prevents the problematic protein from activating the aryl hydrocarbon receptor on human cell membranes, thereby preventing a cascade of cellular processes that would lead to the activation of several harmful genes.
  • Green tea polyphenols reduce levels of IGF-1 in mouse prostate tumor cells that resemble closely those occurring in human prostate cancer, according to a 2004 research paper from the University of Wisconsin and Case Western Reserve University. Increased levels of insulin-like growth factor-1 (IGF-1) are associated with higher risk of prostate, breast, lung and colon cancer.
  • Finally, researchers at Japan’s Kyushu University reported late last year that EGCG inhibits tumor growth by binding to a cell receptor called 67-kDa laminin, which is believed to promote the spread of cancer cells through the body.

Even though tea’s active compounds are generally considered antioxidants, new research suggests that, ironically, they may exert some of their anti-cancer effects—i.e., promotion of spontaneous cancer cell “suicide” (apoptosis)—through their role as pro-oxidants, which occurs in certain contexts.



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