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By Daniel Gastelu Section 5. Green Tea Green Tea-a bioflavonoid-containing plant product-has been enjoyed as a hot beverage and an herbal remedy in China and Japan for thousands of years. Recently, researchers have investigated green tea's healing properties and have discovered some interesting health benefits, which include protection against certain infections; improved cardiovascular health; better dental hygiene; and protection from developing some types of cancer. Q. What exactly is green tea? A. There are many different types of teas available these days. Some are sold as herbal teas to distinguish them from black tea. Green tea and regular tea come from the same plant-the Camellia sinensis shrub, which is native to Asia. The leaves of Camellia sinensis are dried and cured in different ways to yield different types of tea. Black varieties of tea, which are very popular in European countries and the United States, are prepared by processing, fermenting, and drying the tealeaves. Green tea does not undergo fermentation. Instead, the leaves are steamed, dried, and ready for use. The steaming inactivates enzymes present in the tealeaves that can slowly break down the bioflavonoids. Therefore, the green tea process preserves much of the beneficial nutrient content found in the fresh tealeaves. The black tea varieties undergo chemical changes during the fermentation process, destroying most of the bioflavonoid content. Q. Does green tea contain caffeine? A. Green tea does contain caffeine, but only roughly half as much as a cup of coffee or cola soft drink. Specifically, a 6-ounce cup of green tea can contain 15 to 60mg of caffeine. There are decaffeinated green tea beverages and supplements available for people who want to avoid caffeine. Q. What are the health benefits of green tea? A. Based on experimental studies and research conducted on green-tea consumption in human populations, some of the major beneficial effects of green tea include a reduced risk of many diseases such as heart disease; a reduction of dental problems; a reduced cancer risk, especially gastrointestinal cancer; the maintenance of healthy cholesterol levels; and anti-hypertensive effects. Q. What effect does green tea have on gastric cancer? A. Japanese researchers documented a reduced risk of gastric cancers in populations drinking several cups of green tea per day. According to vital health statistics, the death rate from cancer in both men and women in the Shizuoka region of Japan was found to be much lower than the national average. This epidemiological study led researchers to conduct animal experiments to see if feeding green tealeaves to mice would suppress cancer cell growth. They found that tumor growth in experimental mice fed green tea was indeed suppressed. These results led researchers to take a closer look at the dynamics of green tea in reducing the risk of gastric cancers. They explored which components of green tea were causing the reduction, and what other health effects green tea has on people. In 1998, in the Japanese Journal of Cancer Research, researcher Suminori Kono and coworkers reported their work on the relationship of gastric cancer and diet in the Northern Kyushu region of Japan. Their research supported the findings of other researchers: A decreased risk of gastric cancer was observed among those people with high green-tea consumption-ten or more cups a day. Q. How does green tea produce this anti-gastric cancer effect? A. One way researchers believe that green tea reduces the risk of gastric cancer is that the bioflavonoids it contains has the ability to inhibit the activity of a mutagen-causing chemical called N-methyl-nitro-N-nitroguanidine. In laboratory studies, this chemical as been shown to cause stomach cancer in animals. Upon investigation, researchers determined that the major group of bioflavonoids primarily responsible for this protective action against gastric cancer is the catechins. It's important to note, however, that the other bioflavonoids present in green tea also contribute to green tea's health benefits. Usually, all the phytonutrients contained in any plant work together for maximum benefit. This is known as synergism-a complementary, effect. It means that while certain activities of individual types of bioflavonoids or other phytonutrients can be determined, they seem to work better in the body when the entire phytonutrient family is present. In 1992, Dr. Hans Stich reported his research findings in Preventative Medicine, supporting the notion that the phytonutrients in green tea cause a chemo protective effect, or offer protection against cancer-causing chemicals, in the digestive system by inhibiting the formation or action of carcinogens in the diet. He found that green tea inhibited the formation of mutagenic nitrosamine products, which are suspected of causing gastric cancers. Their inhibition can be beneficial, possibly reducing the risk of gastric cancers. Q. Can drinking a lot of tea increase the risk of cancer in certain circumstances? A. As Dr. Stich points out, there are contradictory results reported in the research concerning the consumption of black tea, not green tea. High consumption of black tea, which has a lower amount of nutrients than green tea, has been linked to an elevated risk of cancer in populations that have high intakes of potent black teas. One of the components in black tea often suspected of having beneficial effects at low dosages, and possible toxic effects at high dosages, is the tannins. That is one of the reasons why many cultures add milk to the various varieties of black tea. Certain substances in milk bind to tannins, reducing their possible detrimental health effects. Remember, these potential adverse effects are from drinking black tea, not green tea. Furthermore, many studies have documented the beneficial health effects derived from drinking black tea. Q. What about the cardiovascular benefits associated with drinking green tea? A. There is some evidence that consumption of green tea can reduce the risk of cardiovascular diseases, such as heart attack and stroke. This can be accomplished by keeping the levels of cholesterol in the blood within a normal range. Dr. Suminori Kono conducted a study on 1,306 men who drank nine or more cups of green tea daily. He found them to have lower total cholesterol levels than non-green tea drinkers. He further determined that increased consumption of green tea raises the so-called "good" high-density lipoprotein cholesterol (HDL), while lowering the so-called "bad" low-density lipoprotein cholesterol (LDL) and the very-low-density lipoprotein cholesterol (VLDL). Other studies on animals and humans confirm these cardiovascular benefits. In particular, one study conducted on adult males and females consuming 500mg of green tea catechins-equivalent to five cups of normal green tea brew-reported the following results: lower blood pressure; increased HDL-cholesterol; and an improvement in bowel movements, promoting regularity. Finally, a health survey conducted by Yoshikazu Sato and coworkers reported that among the 9,510 non-alcohol drinking, nonsmoking women over forty years of age, the incidence of stroke and cerebral hemorrhage was significantly lower in those women who drank five or more cups of green tea a day. Q. What other health benefits does green tea have? A. Due to the naturally occurring amount of fluoride in green tea, as well as the anti-bacterial action of its tannins, studies on animals have confirmed the dental-caries-inhibiting effect of green tea. Thus, green tea may be used as a preventative of dental cavities. Other benefits of drinking green tea before, during, and after meals includes antibacterial action, antioxidant effects, reduction of blood-glucose levels, as well as the anti-gastric cancer effects mentioned previously. Researchers believe that the glucose-suppressing effect of green tea may benefit people on weight management programs and may be useful in treating or even preventing diabetes. Topping all of these health benefits is the research conducted by Shoichi Sadakata and coworkers, who examined the longevity effects experienced among female practitioners of chanoyu-Japan's traditional tea ceremony. The 3,380 female practitioners of chanoyu were followed over an eight year period. Sadakata found that the women who drank green tea had a lesser risk of death from all causes than compared to the population norm. Q. What's the best way to take green tea in order to get all these health benefits? A. In general, people benefit most from drinking some green tea and taking supplements containing green-tea extracts. When selecting dietary supplements, look for brands with green-tea extracts standardized to 25-percent or more polyphenols. As part of a total dietary supplement plan, green-tea extract intake of 50mg or higher will be beneficial, with amounts of 300 to 500mg yielding therapeutic results. Take green tea supplements before or with your meals and enjoy a cup of green tea often.
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