Green Tea & Cancer - Read what noted Oncologist Dr. Mitchell Gaynor's has to say about green tea. Select from our updated articles database for specific cancers:
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.
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.
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 Recommends Our Tea to His Patients
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.