Primarily for those drinking green tea to heal through its active ingredient: Catechin. Tannin in green tea is mostly catechin and forms a key component in its astringent taste.
Green Teas Effects on Cancer - Green tea research has shown it has an effect on variety of cancers. Read what noted Oncologist/author Dr. Mitchell Gaynor's has to say about green tea. He recommends our tea to his patients.
From Dr. Gaynor's Cancer Prevention Program - Chapter 19 - Green Tea “Men occasionally stumble over the truth, but most then pick themselves up and hurry off as if nothing had happened.” – Winston Churchill
In 1991 a witty staff writer at Science News wrote an article entitled “Tea-Totaling Mice Gain Cancer Protection.” He was right. Your total tea intake, if it’s high enough, could put you in good company with those lucky mice. Tea, particularly green tea, is one of the most potent cancer preventive agents found in the human diet. Two to five cups a day might change your life.
Tea drinking is an ancient human invention, and tea is- next to water- the most widely consumed beverage on the glove. I do have hopes that in this country, the public will discover tea in a very big way. Already, a smattering of tea shops and tea bars are opening across America. People are discovering the wide variety of teas distributed by large importers of fine tea. I talked with the founder of one such company, John Harney and Sons Tea in Salisbury, Connecticut who stated, “Tea is going to be the coffee of the twenty-first century, the way things are going. It’s not just that a cup of tea has less than half the caffeine of a cup of coffee, but once people try a fine tea, they don’t want to go back to the supermarket teas.”
All teas come from the same tropical or semi tropical evergreen plant, the Camellia species of the Theaceae family. Thus, the leaves for both green and black teas are the same; it’s the different processing techniques that determine their color, taste, and chemical properties. Green teas, like Darjeeling and Sensia, are more delicate and mild, whereas English teas are Black-tea blends, robust enough for the addition of milk and sugar. (some studies indicate that adding dairy products to tea inactivates tea’s cancer preventive polyphenols.) More than 2.5 billion pounds of tea are produced yearly, but 80 percent of this is black, and the remaining 20 percent is largely consumed in the Orient.
Why Your Tea Should Be Green
Green tea is tea in its freshest, least processed form. The tea leaves are steamed to soften them, then rolled and dried. Black tea suffers a good deal more to make its way to your teacup. The leaves are withered by air or heat, the broken so that oxygen interacts with enzymes in the leaf. This begins a process of fermentation that darkens the tea and continues until it is heated to make your drink. Variations in technique as well as variations in the leaves lead to the almost infinite variety of black teas.
Unfortunately, all this flavorsome mistreatment produces major losses in the most nutritionally significant portion of the brew. All teas contain easily measurable quantities of antioxidants and powerful polyphenols with demonstrated anticancer effects. The levels of these items are far higher, however, when the tea is green rather than black – approximately six times as many polyphenols per cup. As for antioxidant protection, let’s simply start by noting that 2 small cups of green tea contain as much vitamin C as 1 glass of orange juice. The major polyphenol of green tea was reported at the American Chemical Society’s 1997 meeting in Las Vegas to be 200 times more potent than vitamin E and 500 times more potent than vitamin C as an antioxidant.
The real distinction of green tea, however, is in its polyphenolic compounds-flavonols, flavondiols, flavonoids, and phenolic acids-some of which are really not very widely distributed in other foods. These compounds account for up to 30 percent of the dry weight of green tealeaves. The polyphenols in green tea that appear to be most important in cancer protection are called catechins. One in particular, epigallocatechin-3-gallate (EGCG), is -- in addition to being the most potent of the green tea antioxidants -- believed to block the carcinogenic effects of a number of infamous cancer-inducing chemicals. Some of the other major catechins in green tea with apparent anticancer effects are EC2, ECG, and EGC- an alphabet soup that spells only good things for you
Cancer researchers have been hot on the trail of the catechins ever since a 1994 study in the Journal of the National Cancer Institute pointed out that green tea drinkers in Shanghai cut their risk of esophageal cancer by 60 percent if they were women and 57 percent if they were men. Most of these people were drinking 2 to 3 cups of green tea a day. This news caused many a medical brain cell to switch on, especially when combined with a presentation made a few years earlier at an American Chemical Society meeting. Then, it had been pointed out that Japanese smokers who drank green tea lowered their risk of lung cancer by 45 percent, which certainly seems to explain why the green tea- drinking Japanese have both the highest smoking rates and the lowest lung cancer rates in the developed world. Another Japanese study found significantly decreased risk of gastric cancer among people who drank more than 10 cups of green tea daily.
If you’re feeling relieved that you don’t live in a province in China where esophageal cancer rates are so high, consider the fact that incidence rates in the United States have tripled since 1970s. Esophageal cancer will claim almost 10,000 lives in 1998 in the United States alone. In 1994, a 10-year study was presented at the General Motors Cancer Research Foundation Scientific Conference held in Bethesda, Maryland. In this study, conducted by the University of Washington Medical Center in Seattle, researchers found they could predict cancer risk by examining cells for abnormal amounts of DNA(called aneuploidy) in biopsies of patients with a condition know as Barrett’s esophagus. This condition is caused by chronic indigestion and is a first step toward cancer. It is estimated that 5 million Americans have Barrett’s esophagus and 5 percent of those will go on to develop cancer within 5 years. Seventy-five percent of the patients who tested positive for abnormal amount of DNA developed cancer or pre-cancer, compared to none of those with normal amounts of DNA.
I have strongly recommended green tea to virtually all my patients who come to me looking for cancer protection. Because of the Japanese and Chinese statistics, I recommend it twice as hard when the lungs or esophagus are in question.
Here’s a case you can’t help but enjoy. Richard Dunn, a cabinetmaker from Connecticut, was 38 years old when he came to see me, referred by a chest surgeon at Cornell Medical Center in New York who had recently operated on him. Richard was a career smoker: he started his tow-pack-a-day habit when he was 15 years old. Tow month before he visited me, he had seen his doctor because of a severe cough that had lingered on in the aftermath of a cold.
Well aware of his recreational puffing, Richard’s doc had ordered up a chest X-ray. There in the middle of his left lung was an ominous spot half the size of a dime that represented a small nodule or bump. The results of a biopsy were inconclusive. The possibility of lung cancer was very real, and Richard decided to have surgeon take the mysterious object out. It turned out to be non-cancerous tissue resulting from inflammation.
Richard came to see me two weeks later, vigorously struggling after his recent fright not to resume smoking again. I found out right away that both his parents had been two-pack-a-day smokers, too, and his father had died of lung cancer at age 51. I asked him what effect that had had on him. : “Of course, it made me leery of continuing to smoke.” Richard said, “but you’ve got to remember I started pretty young. Quitting just wasn’t something I was able to do.”
In designing cancer protection for Richard, I had two goals in mind: first, to make it as easy as possible for him to maintain his present abstinence from the killer weed, and second, to load up his body with every cancer preventive agent I could think of. He already had a quarter century of smoking under his belt and, even if he never took another puff, his risk for lung cancer would always be significantly higher that a non-smoker’s.
Richard was highly motivated, and I took care of the first part of my plan by recommending that he try some of the breathing and relaxation techniques that you’ll read abut in Chapter 20. I knew that less stress not only would make him a happier person but would make it easier for him deal with the additional stress of quitting an addictive drug.
The second part of my plan was a regimen of cancer preventive agents. I asked Richard to drink 3 to 4 cups of green tea a day and to consume soy in the form of miso and tofu. Then I asked him to juice daily-a mix of tow celery stalks, two carrots, one beet, one apple, one serving of watercress, and a quarter head of cabbage. Finally, Richard began consuming algae and grass juices on a daily basis and eating a designer food that contained the various bee products you’ve read about in Chapter 10.
In the three years since Richard first saw me, his X-rays have remained clean. His exercise ability and pulmonary stamina have markedly improved, and Richard now tells me that getting that lump in his lung was the best things that ever happened to him. He’s probably right.
A Real Rodent Tea Party
Results of studies on tea conducted in humans so far are intensely suggestive but still preliminary. Results of studies conducted in animals-who wouldn’t normally be drinking green tea at all-are formidable and highly satisfying to anyone who would like to achieve phytonutrient-driven cancer prevention. They have demonstrated that the polyphenols in green tea give mice protection against all stages of cancer: tumor initiation, tumor promotion, and tumor progression.
Here is a description of a few of the most impressive animal studies:
American researchers found that in mice, green tea extract taken in water inhibited the development of skin tumors caused by ultraviolet-B(UBV) light. The extract also inhibited lung cancer caused by the consumption of a nicotine-derived nitrosamine.'
Green tea extract in water was shown to inhibit cancer in rodents in such organs as the stomach, duodenum, colon, liver, and pancreas.
Benign tumors can, of course, often become malignant, and one recent study showed that this process - at least for skin cancer – can be slowed or halted in mice by the application of green tea pholyphenols to the warts and polyps that were in the process of being converted to carcinomas.
Green tea mildly inhibits certain enzymes (Phase 1 enzymes) that serve to activated cancer-causing chemicals in our bodies. For instance, a variety of animal studies have shown that it prevents nitrosamine-induced cancer of the stomach. These are the largest single group of cancer-causing chemicals in our diet and are especially prevalent in well-cooked or smoked meat or fish, as well as in tobacco smoke.
Up From Rodents
Meanwhile, we continue to see strong hints in human-population studies that ea can only help you.
A 1995 study of cancer in postmenopausal women in Iowa revealed an inverse association between tea consumption- presumably; this would have been mostly black tea- and cancer risk for esophageal, stomach, and kidney cancers. In other words, drinking tea reduced the chance of developing these cancers.
An intriguing report came from Itaro Oguni, Ph.D., at the University of Shizuoka in Japan in 1989. He compiled statistics showing that the mortality rate from total cancers and also from stomach cancer (one of the predominant Japanese malignancies) were significantly lower in Shizuoka Prefecture, the leading tea-producing area in Japan.
Finally, I believe I have saved the best for last. If the evidence of Japanese researchers is to be believed, it may well be that the growth rates of already-developed cancers are radically slowed when green tea is consumed in sufficient quantities. Doctors at the Saitama Cancer Center in Japan made a study of the survival rates of patients with cancer relative to their green tea consumption. The astonishing results showed that patients who drank more than 10 cups per day died 4.5 years(men) to 6.5 years (women) later that did the patients who drank fewer than 3 cups per day. Relatively few conventional cancer treatments claim comparable statistical impact.
Green Tea is NOT Simply a Cancer Fighter
Green tea, the phytonutrient champ, has also been shown to lower cholesterol levels and reduce the rate of stroke, perhaps because some of the catechins make the platelets in your bloodstream less sticky. Platelets are the little saucer-shaped cells involved in blood clotting, and if they clump together excessively they can block up an artery, causing a heart attack or stroke. Another benefit is green tea’s antioxidant power, which is so great that lab work has shown that it is 200 times more effective than vitamin E. Tea pholyphenols have also been found to be strong inhibitors of the acquired immunodeficiency syndrome(AIDS) virus replication system. In addition, they possess antibacterial and antifungal properties. In experimental studies, for example, tea polyphenols have been found to enhance B-cells, a key part of our immune system. In Japan, a study was done in which tea was given to the students at one school who gargled with it in an attempt to counteract an influenza outbreak that was then raging. The researchers concluded that it was quite effective and noted that no class in the school was closed during the outbreak.
What’s the bottom line here? We recommend that you drink green tea without reservation.
Pharmacist’s Corner
Studies show that adding milk to green tea decreases the antioxidant activity of the tea catechins. Epidemiologic studies show that there is not much difference between tea drinkers and non-tea drinkers in countries where it is customary to add milk to tea.
Drink at least one cup of green tea three times daily. From Dr. Gaynor's Cancer Prevention Program
by Mitchell L. Gaynor, Jerry Hickey, William Fryer
Publisher: Kensington Pub Corp; (January 1999)
Dr. Mitchell Gaynor has directed medical oncology at the renowned Strang Cancer Prevention Center in New York City. His mother died of breast cancer when he was 9, and he's made it his mission to spare other people the pain his family endured. Gaynor is concerned with the ubiquitousness of pesticides, herbicides, and other environmental toxins linked to cancer (the U.S. has made the use of DDT illegal, but regularly exports it to Third World countries for use on crops that are harvested and imported back to the States). He says, "even those of us who don't smoke, eat a high-fat diet, and don't work in a chemical plant are still living, at work and at play, on a profoundly soiled an carcinogenic planet." The best defense against this, says Gaynor, is a diet high in phytonutrients and antioxidants, from catechin in green tea to carotenoids in carrots and cantaloupe, to resveratrol found in red grapes, and zeaxanthin in tomatoes.
Green Tea & Cancer - Epidemiological observations have shown that people in green-tea consuming countries-mainly Japan and China-have very low rates of cancer.
In Japan, the women who teach the tea ceremony, and thus drink more than the average amount of extra-strong green tea, are noted for their very low mortality rate and longevity; deaths from cancer are especially rare in this group.
The rates of breast, colon, skin, pancreatic, esophageal and stomach cancer have been found to be lower among drinkers of green tea. If those who consumed more than ten cups of green tea a day got cancer, it was at considerably older age, especially in women. Likewise, it has been noted that those Japanese smokers who consume a lot of green tea seem to enjoy protection against lung cancer. In fact, the Japanese have both the highest smoking rate and the lowest lung cancer rate in the industrialized world.
Western epidemiological studies have also tended to confirm that higher consumption of tea and coffee is associated with a lower risk of breast cancer. On the basis of a number of such epidemiological studies, it could be tentatively asserted that the higher the consumption of tea in general, and perhaps of green tea in particular, the lower the incidence of breast, prostate and lung cancer. The same probably holds true for colon, stomach, pancreatic and skin cancer. In vitro or animal research indicates that green tea may be effective against an even wider variety of types of cancer, including leukemia and glioma.
While green tea, and possibly black tea as well, show great promise mainly as chemopreventive agents, there is now mounting evidence that the active compounds in tea are an effective adjuvant therapy for the treatment of cancer, particularly when combined with other natural anti-cancer agents such as curcumin, or with conventional drugs such as tamoxifen or chemotherapy. Finally, tea and green tea extract can also be used for prevention of recurrence and metastasis.
Obviously, the anti-cancer mechanisms of green tea polyphenols are complex, and not yet completely understood. Research at the level of molecular genetics is particularly promising. We already do know enough to state with certainty that green tea is an effective chemopreventive agent. And we also know that it is best to use several anti-cancer agents (including all the major antioxidants) for synergistic prevention along all the possible pathways. Green tea works along so many pathways that it is simply an indispensable part of any serious cancer-prevention program.
Green tea catechins are among the phenolic compounds known to suppress the formation of tetracycline amines and antihistamines, known to be potent carcinogens. Antihistamines have been tentatively linked to brain cancer and leukemia. Drinking green tea with or after a meal containing meat cooked at a high temperature or treated with nitrites seems to offer a degree of protection.
Many other carcinogens are likewise rendered less harmful thanks to the action of green tea polyphenols on inducing enzymes that detoxify various undesirable compounds, and inhibiting those enzymes that would make certain carcinogens bioactive. Glycerolize (conjugation with luxuriance acid) is another detoxifying mechanism that is enhanced by catechins.
Yet another study suggested that tea polyphenols (including black tea theaflavins) induce the release of hydrogen peroxide as the mechanism of causing cancer cell apoptosis. Purified polyphenols were more powerful apoptosis inducers than green tea extract and decaffeinated green tea.
It has been also postulated that green tea catechins inhibit the activation of protein kinase C, and interfere with the binding of growth factors to their receptors. (In the case of breast cancer, catechins were in fact shown to interfere with the binding of estrogen to estrogen receptors.) Catechins were also found to inhibit the release of tumor necrosis factor alpha (TNF-alpha), a highly inflammatory cytosine, and of nitric oxide syntheses, an enzyme necessary for the production of nitric oxide (nitric oxide plays an important role in inflammation and carcinogens).
A particularly exciting study, done at the Cancer Chemotherapy Center in Tokyo, Japan, and using leukemia and colon cancer cell cultures, demonstrated that "epigallocatechin gallate strongly and directly inhibits ateliers." Ateliers. is the enzyme that "immortalizes" cancer cells by maintaining the end portions of the tumor cell chromosomes. Even in the presence of non-toxic concentrations of epigallocatechin gallate, cancer cells exhibited telomere shortening and senescence. Thus, inhibition of ateliers. could be one of the main anti-carcinogenic mechanisms of catechins.
Green Tea & Tumor Growth (tNOX) -
The most recent study, done at Purdue University and presented at the 1998 meeting of the American Society for Cell Biology, discovered another major mechanism.
The authors, the husband and wife team of Dorothy and James Morre, claim that the main tumor-inhibitory mechanism of green tea may stem from its ability to interfere with the enzyme quinol oxidase, generally referred to as NOX. This enzyme is required for growth by both normal and malignant cells. While normal cells express NOX only when dividing, tumor cells express it all the time. The tumor form of the enzyme is called t-NOX, or tumor-associated NOX. Drugs that inhibit tNOX also inhibit tumor growth.
While both black and green tea infusions inhibited tNOX in various cancer lines, green tea was able to achieve these results at much greater dilutions, indicating higher concentrations of the active compound or compounds. By selectively testing for active compounds, the authors of the study concluded that epigallocatechin gallate was the active agent responsible for inhibiting tNOX - while sparing the NOX of healthy cells. Dr. Dorothy Morre stated, "In the presence of epigallocatechin gallate, the cancer cells literally failed to grow or enlarge after division. Then, presumably because they failed to reach the minimum size needed to divide, they underwent programmed cell death, or apoptosis."
While the inhibition of ateliers. and of tNOX may be the chief anti-carcinogenic mechanisms of green tea polyphenols, or at least two very important ones, there is little doubt that green tea catechins act along several different pathways and interact with a variety of enzymes to produce their anti-cancer effects.
It should also be noted that green tea lowers serum glucose and consequently insulin (this will be discussed in detail in the second article on green tea). Since elevated insulin is a potent growth factor for many kinds of tumors, as well as a pro-inflammatory and immunosuppressive hormone, the lowering of insulin in itself should help prevent cancer or, in cases of existing cancer, slow down its growth.
Green Tea, Angiogenesis & Metastasis Prevention - The latest good news about green tea comes from a study done at the Karolinska Institute in Stockholm. A team of researchers headed by Dr. Yihai Cao found that green tea can
block angiogenesis-the development of new blood vessels that tumors need in order to grow and metastasize. The authors gave mice the equivalent of two-to-three cups of green tea a day. When lung cancer was induced, the mice supplemented with green tea showed significantly less tumor growth. The scientists found that green tea suppressed the development of new blood vessels and prevented metastasis. They hypothesize the epigallocatechin gallate is the compound responsible for the suppression of angiogenesis.
In an interview, Dr. Cao explained that all solid tumors depend on angiogenesis for their growth. If green tea polyphenols can prevent angiogenesis, then this would go a long way toward explaining why green tea is effective in preventing so many kinds of cancer. Dr. Cao stressed that it takes long-term consumption of green tea in order to obtain these chemopreventive benefits.
The anti-angiogenic potential of green tea could also be used for the prevention and possibly even the treatment of degenerative eye disorders, such as diabetic retinopathy, that also depend on the development of new blood vessels. Studies done by the Molecular Biology Laboratory, National Cancer Research Institute (IST), Genova, Italy demonsatrted that epigallocatechin gallate (EGCG), a flavonoid from green tea that possesses chemopreventive activity in experimental and epidemiological studies, is a potent inhibitor of MMP-2 and MMP-9. In addition, inhibition of angiogenesis may be another mechanism in which green tea helps prevent heart disease, since atherosclerotic plaque also needs to develop microcirculation to keep growing. (Note the recent news about how the anti-angiogenetic drug endostatin slows the development of atherosclerosis.)
Green tea has also been shown to help prevent metastasis. Cancer cells secrete special enzymes called collagenases in order to penetrate and colonize various tissues. It is the metastatic process that is lethal, not the primary tumor. Hence finding substances that can prevent metastasis is of prime importance in fighting cancer. A study done at the University of Shizuoka in Japan found that epigallocatechin gallate does in fact inhibit the secretion of collagenases by tumor cells (in this study, highly metastatic lung cancer cells), thus arresting their ability to invade normal tissue. Black tea theaflavins were also effective. There is also additional evidence that green tea polyphenols help inhibit angiogenesis, or the growth of new blood vessels that nourish the tumor.
Two of the green tea polyphenols, epigallocatechin-3-gallate and epicatechin-3-gallate, have been found to be effective inhibitors of 5 alpha-reductase type I, reducing the synthesis of DHT, a potent form of testosterone implicated in causing prostate enlargement and prostate cancer. Epigallocatechin gallate has also been found to be the most potent catechin in inducing apoptosis in human prostate cancer cells when tested on various cell lines. Together with lycopene and selenium, green tea should be considered as a special prostate-protective agent.
Green Tea & Radiation Damage - Protection against radiation-induced DNA damage is yet another area where green tea has had positive effects. A recent National Cancer Institute study found that green tea catechins can
protect cells against radiation damage. Using chromatid breaks as a marker for unrepaired DNA strand breaks, it was found that all catechins except, interestingly, epigallocatechin gallate, significantly reduced DNA radiation damage. Curcumin had a similar effect. The authors speculate that the protective mechanism is due to the ability of polyphenols to scavenge the particularly dangerous hydroxyl radical. They conclude that catechins and other plant polyphenols can protect human cells against radiation damage.
Green Tea & Breast Cancer
- A recent Japanese study of 472 women with various stages of breast cancer explored in greater detail the epidemiological findings on green tea's protection against breast cancer.
In this case, women with stage I, II and III breast cancer were assessed in terms of their green tea consumption. It was found that "premenopausal women who consumed more green tea had a lower number of lymph node metastases. In postmenopausal women greater consumption of green tea correlated with increased expression of the estrogen and progesterone receptor, which implies more differentiated tumor cells and better prognosis." Finally, in a seven-year follow it was found that "women with stage I or II cancer who consumed five or more cups of green tea a day had approximately half the recurrence rate of those women who consumed four cups or less." Researchers at the Department of Surgery, Division of Oncology and. Center for Human Nutrition, University of California found that Inhibition of VEGF transcription appeared to be one of the molecular mechanism(s) involved in the antiangiogenic effects of green tea, which may contribute to its potential use for breast cancer treatment and/or prevention.
One way in which green tea helps protect against breast cancer is by enhancing glucuronization of estrogens in the liver, a process through which estrogens are rendered inactive by being conjugated with glucuronic acid, a form in which they are excreted from the body. Perhaps it is mainly this mechanism that also accounts for lower estradiol levels found in those Japanese women who consume a significant amount of green tea. (Another mechanism might involve higher levels of sex hormone binding globulin found in women who consume green tea; the authors caution, however, that this might be due to caffeine.)Besides human epidemiological studies, we also have experimental animal studies showing that green tea catechins provide significant protection against breast cancer. One study found that after exposure to a strong mammary carcinogen (DMBA), the survival rate in the group of rats fed a diet enriched with 1% green tea catechins was 93.8%, compared with only 33.3% in the control group. The tumors in the green tea group were also significantly smaller.
Epigallocatechin gallate alone was also found to inhibit tumor growth of human mammary cancer transplanted into mice. A study done at the College of Pharmacy at the University of Arizona likewise singled out epigallocatechin gallate as the most effective of the green tea catechins in its anticancer effects in regard to breast cancer, colon cancer and melanoma.
A team of scientists led by Dr. Radha Maheshwari, professor of Pathology at the Uniformed Services University of the Health Sciences (USU) and Rajesh Loganathan Thangapazham, a graduate student, have shown that green tea has antitumor effect in breast cancer cells. The recently concluded study will be published in the Journal of Cancer Biology and Therapy, December 2007, Volume 6, Issue 12.
Dr. Maheshwari’s study observed that green tea can inhibit the invading capacity of these breast cancer cells and have also identified the mechanisms involved in death inducing and invasion inhibiting effects of green tea.A study by Dr. Maheshwari that was published earlier this year in Cancer Letters showed that green tea is effective in delaying tumor incidence as well as in reducing the tumor burden. Green tea was found to inhibit growth of tumors as well as induce death of breast cancer cells.
Green Tea & Ovarian Cancer - Recent results in Dec 2005 from a study conducted at the Karolinska Institute in Stockholm, Sweden, show a relationship between the amounts
of tea a middle-age woman drinks and her risk for ovarian cancer.
The study, was published in the Dec. 12 issue of Archives of Internal Medicine. The researchers studied medical records of more than 61,000 women ages 40 to 76 who were part of a cancer survey. The women were also asked about their diets between 1987 and 1990. Fifteen years later, far fewer tea drinkers had been diagnosed with ovarian cancer. "We observed a 46 percent lower risk of ovarian cancer in women who drank two or more cups of tea per day compared with nondrinkers," the researchers reported.
Also, women who drank one cup of tea per day had a 24-percent decrease in the incidence of ovarian cancer. The researchers contend a link between tea drinking and decreased ovarian cancer incidence is present as each additional cup of tea per day was associated with an 18 percent lower risk of ovarian cancer. The chemical specifically linked to protection from ovarian cancer has not been determined. Green tea has also shown promise in other areas. For one, it enhances the effectiveness of chemotherapy in ovarian cancer. A study done at the University of Shizuoka, Japan, discovered that oral administration of green tea or theanine, an amino acid found in the leaves of green tea, synergized with the chemotherapy drug Adriamycin in lowering tumor weight. Adriamycin alone was ineffective. Theanine nearly tripled the concentration of adriamycin in the tumor tissue, while decreasing adriamycin levels in healthy tissue. In a more recent study, the same authors showed that theanine also synergizes with Adriamycin to inhibit liver metastases of ovarian cancer. This adds to the growing evidence that natural agents such as green tea can greatly enhance the effectiveness of conventional therapies.
In a study conducted on ovarian cancer patients in China, researchers found that women who drank at least one cup of green tea per day survived longer with the disease than those who didn’t drink green tea. In fact, those who drank the most tea, lived the longest.
Green Tea & Prostate Cancer
- In the first known study of the absorption and anti-tumor effects of green and black tea polyphenols in human tissue, researchers at the University of California at Los Angeles were able
to detect tea polyphenols in prostate tissue after a very limited consumption of tea. The study was reported at Experimental Biology 2004, in Washington, D.C., as part of the scientific program of the American Society of Nutritional Sciences, one of the six sponsoring scientific societies of this large multi-disciplinary meeting.The scientists found that prostate cancer cells grew more slowly when placed in a medium containing blood serum of men who had consumed either green or black tea for five days compared to serum collected before the men began their tea-drinking regimen. Serum from men who drank comparable amounts of diet or regular soda showed no such slowing in cancer cell proliferation.
Research by Curtin University in Perth Western Australia has shown Green tea drinking over a long period of time helps prevent prostate cancer. Professor Colin Binns studied long time drinkers in China. The big sippers who'd been imbibing for 20 years were 2/3 less likely to develop the cancer than the control group.
Laboratory studies have found that green tea extracts prevent the growth of prostate cancer cells in test tubes. In a large study conducted in Southeast China researchers found that the risk of prostate cancer declined with increasing frequency, duration and quantity of green tea consumption.
Green Tea & Leukemia - Leukemia is yet another disease where green tea may prove effective as an adjuvant therapy for treatment. The particularly bioactive catechins in green tea, epigallocatechin gallate, was found
to inhibit the proliferation of human and mouse leukemic cells in vitro.
The Drug Discovery Program, of the H. Lee Moffitt Cancer Center and Research Institute reported that the tea polyphenol (-)-epigallocatechin (EGC) inhibits DNA replication in three leukemia cancer cell lines, Jurkat T, HL-60 and K562. Among all the tested tea polyphenols, EGC was found to be the most potent in accumulation of S phase cells and inhibition of the S-G2 progression. In addition, EGC-mediated inhibition of S phase progression results in induction of apoptosis, as determined by sub-G1 cell population, breakage of endonuclear DNA, cleavage of poly(ADP-ribose) polymerase and loss of cell viability. Even at the lower concentration, DNA synthesis by leukemic cells was reduced by more than 50%, while normal cells were unharmed. Another study, using the leukemic blast cells from patients with acute myeloblastic leukemia, a particularly aggressive and often deadly form of leukemia, found that epigallocatechin gallate inhibited the effect of tumor necrosis factor alpha and other growth factors. Consistent with the putative role of green tea in cancer prevention, tea polyphenols have been shown to inhibit tumor cell proliferation by inducing G1 or G2/M cell cycle arrests, also documented is their ability to induce apoptosis (programmed cell death).
Preliminary research released by the Mayo Clinic in Dec 2005 showed that four patients with CLL appeared to have an improvement in the clinical state of their disease after beginning a regimen of products containing epigallocatechin gallate (EGCG), an extract of green tea sold in drugstores.The Mayo Clinic scientists say they are building on data they had previously gathered showing that EGCG kills leukemia cells from patients with CLL in the test tube by interrupting the communication signals they need to survive."The experience of these individuals provides some suggestion that our previously published laboratory findings may actually translate into clinical effects for patients with this disease," said lead study author Tait Shanafelt, a Mayo Clinic hematologist. The latest findings are published online in Leukemia Research. CLL is a blood and bone-marrow cancer that affects 8,000 to 15,000 new patients each year in the United States, the researchers said.
Yet another study found that green tea extract is a potent nucleoside transport inhibitor, interfering with tumor cells' repair of DNA after chemotherapy. Thus green tea extract "markedly potentiated" the effectiveness of chemotherapy. These findings suggest that epigallocatechin gallate and green tea extract could be used as a nontoxic adjuvant therapy for leukemia. It would also be interesting to examine how green tea polyphenols synergize with such established anti-leukemic alternative treatments as retinoic acid, Vitamin D3, DMSO, curcumin and esculetin.
A study by the Division of Hematology, Department of Medicine, Mayo Clinic, studied the impact of epigallocatechin-3-gallate (EGCG), a known receptor tyrosine kinase (RTK) inhibitor, on VEGF receptor status. Chronic lymphocytic leukemia (CLL) cells synthesize and release vascular endothelial growth factor (VEGF) under normoxic and hypoxic conditions. EGCG significantly increased apoptosis/cell death in 8 of 10 CLL samples measured by annexin V/propidium iodide (PI) staining. EGCG (3-25 microg/mL) suppressed VEGF-R1 and VEGF-R2 phosphorylation, albeit incompletely. Thus, these results suggest that VEGF signaling regulates survival signals in CLL cells and that interruption of this autocrine pathway results in caspase activation and subsequent leukemic cell death.
Green tea may also have a positive effect on chromosome damage in bone marrow. Aflatoxin, a carcinogenic mold-produced toxin commonly found in peanut butter and grain products, is known to cause damage to chromosomes in rat bone marrow cells. One study discovered that giving rats aqueous green tea extract 24 hours before inoculation with aflatoxin gained considerable protection from this damage. Black tea and coffee were not effective, although caffeine helped prevent damage if given 2 hours before the inoculation. The authors concluded that green tea "potently suppressed" chromosome damage in the bone marrow.
Green Tea & Liver Cancer - Another type of cancer where high consumption of green tea seems to make a difference is stomach cancer. Men who consumed 7 cups or more of green tea a day had a 31% lower risk of stomach cancer.
Men who consumed 7 cups or more of green tea a day had a 31% lower risk of stomach cancer. A Japanese in vitro study found that both green tea extract and epigallocatechin gallate caused a concentration- and time-dependent growth inhibition and apoptosis (programmed cell death) in a line of human stomach cancer cells.
Animal studies have shown that green tea helps protect against the development of liver tumors in mice. A recent animal study done at the Alabama A&M University discovered that phytic acid (found in beans and grains) and green tea synergize to significantly reduce the number of preneoplastic lesions. Again, this points to the general principle that two or more natural agents are more effective together.
Green Tea & Pancreatic Cancer - In one large-scale study researchers compared green tea drinkers with non-drinkers and found that those who drank the most tea were significantly less likely to develop pancreatic cancer.
This was particularly true for women -- those who drank the most green tea were half as likely to develop pancreatic cancer as those who drank less tea. Men who drank the most tea were 37% less likely to develop pancreatic cancer. However, it is not clear from this population-based study whether green tea is solely responsible for reducing pancreatic cancer risk. Further studies in animals and people are needed before researchers can recommend green tea for the prevention of pancreatic cancer.
Green Tea & Stomach Cancer - Another type of cancer where high consumption of green tea seems to make a difference is stomach cancer. Men who consumed 7 cups or more of green tea a day had a 31% lower risk of stomach cancer.
A Japanese in vitro study found that both green tea extract and epigallocatechin gallate caused a concentration- and time-dependent growth inhibition and apoptosis (programmed cell death) in a line of human stomach cancer cells.
A recent animal study done at the Alabama A&M University discovered that phytic acid (found in beans and grains) and green tea synergize to significantly reduce the number of preneoplastic lesions. Again, this points to the general principle that two or more natural agents are more effective together.
Laboratory studies have found that green tea polyphenols inhibit the growth of stomach cancer cells in test tubes, but studies in people have been less conclusive. In two studies that compared green tea drinkers with non-drinkers, researchers found that people who drank tea were about half as likely to develop stomach cancer and gastritis (inflammation of the stomach) as those who did not drink green tea. However, a study including more than 26,000 men and women in Japan found no association between green tea consumption and stomach cancer risk.
Green Tea & Colo-Rectal Cancer - Department of Medicine, Case Western Reserve University reserachers found that green tea constituent epigallocatechin-3-gallate inhibits topoisomerase I activity in colon carcinoma cells.
DNA topoisomerases I and II are essential for cell survival and play critical roles in DNA metabolism and structure. Inhibitors of topoisomerase constitute a novel family of antitumor agents with demonstrated clinical activity in human malignancies. The clinical use of these agents is limited due to severe toxic effects on normal cells. Therefore, there is a need to develop novel, nontoxic topoisomerase inhibitors that have the ability to spare normal cells. Recent studies have shown that green tea and its major polyphenolic constituent, epigallocatechin-3-gallate (EGCG), impart growth inhibitory responses to cancer cells but not to normal cells. Based on the knowledge that EGCG induces DNA damage, cell cycle arrest, and apoptosis, the reserachers considered the possibility of the involvement of topoisomerase in the antiproliferative response of EGCG. Here, for the first time, we show that EGCG inhibits topoisomerase I, but not topoisomerase II in several human colon carcinoma cell lines. Based on this study it is tempting to suggest that combination of EGCG with other conventional topoisomerase inhibitors could be an improved strategy for treatment of colon cancer. They concluded the role of EGCG as a chemotherapeutic agent needed to be investigated.
The Laboratory for Cancer Research at the College of Pharmacy of, Rutgers University studied the effects of green and black tea polyphenols on normal human colon mucosa and colon cancers were investigated. The results indicated that tea polyphenols can affect arachidonic acid metabolism in human colon mucosa and colon tumors, and this action may alter the risk for colon cancer in humans.
Elucidating a decade’s worth of conflicting studies of the cancer-fighting benefits of green tea, researchers at Rutgers University have conclusively demonstrated that a standardized green tea polyphenol preparation can prevent the growth of colorectal tumors in a rat model of human colorectal cancer. The researchers believe their findings will pave the way for clinical trials with green tea polyphenols in humans. “Our findings show that rats fed a diet containing Polyphenon E, a standardized green tea polyphenol preparation, are less than half as likely to develop colon cancer,” said Hang Xiao, Ph.D., research associate at the Department of Chemical Biology in Ernest Mario School of Pharmacy of Rutgers University. According to Xiao, these results are consistent with previously published results by the project’s primary investigator, C.S. Yang, Ph.D., professor and chair of the Department of Chemical Biology at Rutgers, which showed that green tea consumption was associated with lower colon cancer rates in Shanghai, China.
Green Tea & Bladder Cancer - Only a few studies have examined the relationship between bladder cancer and green tea consumption. In one study that compared people with and without bladder cancer, researchers
found that women who drank black tea and powdered green tea were less likely to develop bladder cancer. A follow-up study by the same group of researchers revealed that bladder cancer patients (particularly men) who drank green tea had a substantially better 5-year survival rate than those who did not.
Green Tea & Lung Cancer - A study using human lung cancer cell culture found that a combination of catechins rather than epigallocatechin gallate alone was more effective at producing apoptosis (programmed cell death), and the effect was
synergistically increased when catechins were combined with other anti-cancer agents such as tamoxifen (a protein kinase antagonist). This provides additional support for the multi-agent approach to cancer.
Smoking may cause damage to the DNA of various cells, including lymphocytes. One type of damage is sister-chromatid exchange (SCE). SCE rates were found to be elevated in smokers who did not consume green tea. Those smokers who did consume green tea had SCE rates comparable to those of nonsmokers, in spite of the fact that their average daily intake was only 3 cups per day. Coffee failed to show a protective effect.
An animal study, however, did show that caffeine is an important chemopreventive agent in lung cancer protection, and that black tea also has an effect.
While green tea polyphenols have been shown to inhibit the growth of human lung cancer cells in test tubes, few studies have investigated the link between green tea consumption and lung cancer in people and even these studies have been conflicting. One population-based study found that Okinawan tea (similar to green tea but partially fermented) was associated with decreased lung cancer risk, particularly among women.
Green Tea & Oral Cancer - Green tea polyphenols are found to induce apoptosis (programmed cell death) in many types of tumor cells, including oral cancer cells. In a study done by the Department of Oral Biology and Maxillofacial
Pathology, School of Dentistry, Medical College of Georgia, cell growth and invasion assays combined with apoptosis assays were used to examine the effects of green tea extracts, green tea polyphenols, and the most potent green tea polyphenol, (-)-epigallocatechin-3-gallate (EGCG), on normal human keratinocytes and oral carcinoma cells. The results showed that green tea and its constituents selectively induce apoptosis only in oral carcinoma cells, while EGCG was able to inhibit the growth and invasion of oral carcinoma cells. These differential responses to green tea and its constituents between normal and malignant cells were correlated with the induction of p57, a cell cycle regulator. These data suggest that the chemopreventive effects of green tea polyphenols may involve a p57 mediated survival pathway in normal epithelial cells, while oral carcinoma cells undergo an apoptotic pathway. Therefore, regular consumption of green tea could be beneficial in the prevention of oral cancer.
One interesting recent study compared the effects of epigallocatechin gallate, curcumin (a powerful ant-carcinogenic compound from the curry spice turmeric), and the combination of both on an in-vitro model of oral cancer. It was found that epigallocatechin gallate helped arrest tumor cell growth in a different cell-cycle stage than curcumin. When the two compounds were combined, growth inhibition was enhanced, suggesting a synergistic effect.
Green Tea & Esophageal Cancer - Experimental studies have shown that tea and tea polyphenols have anticarcinogenic properties. In the study by University of Southern California Keck School of Medicine, a nested
case-control study design was used to investigate the association between prediagnostic urinary tea polyphenol markers and subsequent risk of gastric and esophageal cancers. One hundred and ninety incident cases of gastric cancer and 42 cases of esophageal cancer occurring in members of the Shanghai Cohort (18 244 men aged 45-64 years at recruitment with up to 12 years of follow-up) were compared with 772 cohort control subjects. After exclusion of cases diagnosed under 4 years follow-up, urinary EGC positivity showed a statistically significant inverse association with gastric cancer was found. The protective effect was primarily seen among subjects with low (below population median) serum carotenes. Similar tea polyphenol-cancer risk associations were observed when the gastric cancer and esophageal cancer sites were combined. The study provides direct evidence that tea polyphenols may act as chemopreventive agents against gastric and esophageal cancer development.
A study done by the College of Pharmacy, Rutgers, The State University of New Jersey, suggest that EGCG was converted to EGC in the oral cavity, and both catechins were absorbed through the oral mucosa through drinking green tea rather than using extracts. Because of the possible application of tea in the prevention of oral and esophageal cancers, the salivary levels of tea catechins were determined in six human volunteers after drinking tea. Saliva samples were collected after thoroughly rinsing the mouth with water. After drinking green tea preparations equivalent to two to three cups of tea, peak saliva levels of (-)-epigallocatechin (EGC; 11.7-43.9 microg/ml), EGC-3-gallate (EGCG; 4.8-22 microg/ml), and (-)-epicatechin (EC; 1.8-7.5 microg/ml) were observed after a few minutes. These levels were 2 orders of magnitude higher than those in the plasma. Taking tea solids in capsules resulted in no detectable salivary catechin level. Holding an EGCG solution in the mouth resulted in EGCG and EGC in the saliva and, subsequently, EGC in the urine. The present results suggest that slowly drinking tea is a very effective way of delivering rather high concentrations of catechins to the oral cavity and then the esophagus.
Studies in laboratory animals have found that green tea polyphenols inhibit the growth of esophageal cancer cells. However, studies in people have produced conflicting findings. One large-scale population-based study found that green tea offered significant protection against the development of esophageal cancer (particularly among women). Another population-based study revealed green tea consumption was associated with an increased risk of esophageal cancer related to stronger and hotter tea. Note that green teas are best prepared and consumed below boiling points at around 175F.
Green Tea & Skin Cancer - Skin cancer, and the protective effects of catechins on the skin, have been studied extensively. Ultraviolet radiation is known to cause inflammation, making the skin more susceptible to cancer.
High doses of epigallocatechin gallate and other catechins are particularly effective in preventing inflammation and skin cancer, especially if delivered in the topical form. Topical epigallocatechin gallate was found to reduce the release of inflammatory prostaglandin's (the E2 series), which play a crucial role in generating free radicals and promoting tumor growth.
Due to its antimutagenic and antitumor activities, green tea is a promising candidate for use in topical formulations for skin cancer prevention. Epigallocatechin gallate (EGCG) is a potent polyphenolic antioxidant extracted from green tea. Cima Labs did a study to determine the influence of several factors on the stability of EGCG in solution to obtain information that would facilitate the subsequent development of topical formulations. A second objective was to determine the stability of EGCG in various solvents in the presence and absence of different antioxidants. It was concluded that glycerin-based vehicles are suitable for stabilizing EGCG as a topical formula.
In a study done by USC/Norris Comprehensive Cancer Center, University of Southern California Keck School of Medicine, 10 separate experiments, mice with established chemically induced or UV light-induced skin papillomas were treated continuously with green tea in the drinking water or with i.p. injections of a green tea polyphenol fraction or (-)-epigallocatechin gallate three times a week for 4-10 weeks. Partial tumor regression or > 90% inhibition of tumor growth, as measured by changes in tumor volume per mouse, was observed in 5 experiments, and marked inhibition of tumor growth (46-89%) was observed in 5 additional experiments. Treatment of the mice with green tea or green tea constituents had an inhibitory effect on body weight increases in several but not all of the studies. Examination of the data from all ten experiments revealed that complete tumor regression occurred in 14 of 346 papilloma-bearing mice (4%) that were treated with green tea in the drinking water or with i.p. injections of green tea constituents, whereas none of the 220 papilloma-bearing control mice treated with only vehicle exhibited complete tumor regression. These observations indicate that oral administration of green tea, i.p. administration of a green tea polyphenol fraction, or i.p. administration of (-)-epigallocatechin gallate inhibited the growth and/or caused the regression of established experimentally induced skin papillomas.
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