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Green Tea and Weight Loss

 

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.
The Green Tea (Catechin) Ingredient May Promote Healthy Weight Loss
Aside from fighting heart disease, cancer, and other diseases, a new study shows that drinking green tea may also fight fat.
The study showed that people who drank a bottle of tea fortified with green tea extract every day for three months lost more body fat than those who drank a bottle of regular oolong tea.  Researchers say the results indicate that substances found in green tea known as catechins may trigger weight loss by stimulating the body to burn calories and decreasing body fat.  The findings appear in the January issue of the American Journal of Clinical Nutrition.
Green Tea: Fat Fighter?
Black tea, oolong tea, and green tea come from the same Camellia sinensis plant. But unlike the other two varieties, green tea leaves are not fermented before steaming and drying.

Most teas contain large amounts of polyphenols, which are plant-based substances that have been shown to have antioxidant, anticancer, and antiviral properties.

However, green tea is particularly rich in a type of polyphenols called catechins. These substances have also been shown to have anti-inflammatory and anticancer properties, but recent research in animals show that catechins may also affect body fat accumulation and cholesterol levels.

In this study, researchers looked at the effects of catechins on body fat reduction and weight loss in a group of 35 Japanese men. The men had similar weights based on their BMI (body mass index, an indicator of body fat) and waist sizes.

The men were divided into two groups. For three months, the first group drank a bottle of oolong tea fortified with green tea extract containing 690 milligrams of catechins, and the other group drank a bottle of oolong tea with 22 milligrams of catechins.

During this time, the men ate identical breakfasts and dinners and were instructed to control their calorie and fat intake at all times so that overall total diets were similar.

After three months, the study showed that the men who drank the green tea extract lost more weight (5.3 pounds vs. 2.9 pounds) and experienced a significantly greater decrease in BMI, waist size, and total body fat.

In addition, LDL "bad" cholesterol went down in the men who drank the green tea extract.

The catechin content varies by amount of green tea used and steeping time. But general recommendations, based on previous studies on the benefits of green tea, are at least 4 cups a day. Green tea extract supplements are also available.

Researchers say the results indicate that catechins in green tea not only help burn calories and lower LDL cholesterol but may also be able to mildly reduce body fat.

"These results suggest that catechins contribute to the prevention of and improvement in various lifestyle-related diseases, particularly obesity," write researcher Tomonori Nagao of Health Care Products Research Laboratories in Tokyo, and colleagues.

Reference
By Jennifer Warner
WebMD Medical News
Reviewed By Michael Smith, MD
on Wednesday, January 26, 2005
http://my.webmd.com/content/article/99/
105398.htm