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Mechanism found for green tea in cancer fight
In research conducted at H. Lee Moffitt Cancer Center & Research Institute in Tampa Florida, a mechanism of green tea polyphenols' ability to cause the death of cancer cells was elucidated. By testing green tea polyphenols effect on prostate cancer cell lines, varying concentrations of the polyphenols were found to diminish a protein called Bcl-XL which protects cancer cells from apoptosis, which is programmed cell death.
Green tea has been shown to prevent several types of cancer in animal models. Human populations who consume green tea have lower rates of stomach, liver, pancreatic, breast, lung, esophageal and skin cancers.
Aslamuzzaman Kazi, PhD, research fellow in the Drug Discovery Program at Moffitt Cancer Center, described the finding: "The higher the concentration, the better the response - meaning more apoptosis, or programming that tells cells to die -- apparently occurring as a result of a greater decrease in Bcl-XL, a protein that protects cancer cells from apoptosis. At all concentrations, response was apparent within three hours."
Pin Dou, PhD, associate professor of oncology, biochemistry, and molecular biology at Moffitt further explained, "Because Bcl-XL is overexpressed in many cancers, it could be a key target in all these cancers and explain why green tea polyphenols (are) able to prevent human cancers in mouse models . . . Data from our laboratory suggests that at least one enzyme may modify Bcl-XL and that it is the actual target of tea. We also want to see if that target is present in all human cancers or just some of them."
Green tea has been shown to lower "bad" LDL cholesterol and serum triglyceride levels. Further, green tea's potent antioxidant effects inhibit the oxidation of LDL cholesterol in the arteries, which plays a major contributory role in the formation of atherosclerosis. "There is considerable epidemiological evidence that tea drinking lowers the risk of heart disease" (FEBS Lett., Aug. 1998, 433(1-2):44-46).
The cholesterol-lowering (hypocholesterolemic) effects of green tea (as well as black tea) have been confirmed by both animal and human epidemiological studies. High consumption of green tea by humans, especially more than 10 cups a day, was found to be associated with higher HDLs and lower LDL and VLDL cholesterol, as well as with various biomarkers indicating better liver health. Lower levels of lipid peroxides in the liver are one well-confirmed benefit of green-tea supplementation found in study after study.
A Japanese study relates, "Green tea catechin acts to limit the excessive rise in blood cholesterol" based on a series of studies reported in 1996 (Journal Nutritional Science Vitaminol., 32:613).
Additionally, some very exciting results were found when rats were fed 2.5% green tea leaves in their diet. The experimental group showed a drop in total cholesterol, low-density cholesterol, and triglycerides. The body weight of green tea-fed rats was 10 to 18% lower than that of rats not consuming green tea. In addition, the activity of antioxidant enzymes superoxide dismutase (SOD) and catalase, and of anticarcinogenic phase-II enzyme glutathione S-transferase (GST), were significantly higher in the green tea group, as was the glutathione level in the liver. There was no liver or kidney toxicity. Thus, the study demonstrated combined cardiovascular and anticancer effects of green tea.
The relation between green tea consumption and serum lipid concentrations were examined using cross-sectional data on 1306 males in Japan. Results indicated that total cholesterol levels were found to be inversely related to the consumption of green tea. "Adjusted mean concentrations of total cholesterol were significantly lower in men drinking nine cups or more a day than in those consuming zero to two cups a day" (Prev. Med. July 1992, 21(4):526-31). No wonder the Japanese people have the longest life span. Most Japanese sip tea all day long.
Green tea also has been shown to elevate levels of HDL, the good cholesterol that helps remove atherosclerotic plaque from arterial walls. Green tea is a natural ACE inhibitor. This is an extra benefit for those with high cholesterol and blood pressure, as published studies show lowered blood pressure in animals and humans given green tea extracts. We recommend one capsule (350 mg) of green tea 95% extract daily, or drinking one to ten cups of green or black tea a day
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Calorie burning properties:
A study has found: "Subjects spent 24 hours in a respiratory chamber designed to measure the rate calories were burned and energy expenditure. Those receiving the green tea experienced what researchers consider a significant increase in both tests. Tea extract subjects burned 4 percent more calories, and overall energy expenditure rose 4.5 percent."
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BELTSVILLE, Md., Oct 10, 2002 (United Press International via COMTEX) -- Common tea can be an effective weapon in the fight against diabetes because it boosts insulin activity in the body by more than 15-fold, scientists at the U.S. Department of Agriculture said Thursday.
Insulin problems lie at the root of the potentially fatal illness diabetes, so researchers hope tea-based treatments will help treat or prevent the disease, which affects 17 million Americans. Not only that, this insulin-boosting phenomenon may explain why tea can help fight heart disease and high blood pressure as well.
"This is just one of the many well-established benefits that tea may have," researcher Richard Anderson, a biochemist at the USDA's Beltsville Human Nutrition Research Center in Maryland, told United Press International.
Tea has a long history as a folk remedy for diabetes in China, the West Indies and central Africa. Over the past 20 years scientists also have uncovered potential benefits from tea against cancer, high blood pressure and infection.
"Tea wasn't the only factor we looked at, but it was the best," Anderson said.
Anderson and his colleague Marilyn Polansky analyzed a host of herbs, spices and plants for any beneficial effect involving insulin, the hormone the body needs to convert sugar into energy. They took fat cells from rats and grew them in test tubes because fat cells are highly sensitive to insulin, Anderson explained. Then, they gave the cells mildly radioactive sugar, insulin, and various tea extracts. The radioactive sugar is easy to track and the more the extracts aided insulin activity, the more sugar the cells would convert.
The scientists found black, green and oolong teas boosted insulin activity the most. This insulin-augmenting effect was seen with both caffeinated and non-caffeinated teas, but not with herbal teas, which do not use leaves from tea bushes.
They also identified tea's most insulin-enhancing chemical, called epigallocatechin gallate. Adding whole or skim milk, nondairy creamers or soy milk appears to soak up tea's insulin-augmenting compounds and inhibit the insulin boost, although these milky sponges may release the tea extracts in the stomach, Anderson said. No absorption problem was seen with lemon juice.
"Hopefully people can get better simply by drinking tea," Anderson said. "These compounds clear from the body quite quickly, some in less than six hours, some less than four. The effects are not going to be that large, so you're going to need to continue drinking tea."
Anderson said his team also found cinnamon showed similar insulin-enhancing power. He suggests tea and cinnamon affects the cell proteins insulin binds to.
Diabetes is a disease where the body either does not make insulin or does not properly use it when it does produce it. The scientists think tea increases the body's sensitivity to insulin by setting off a chain reaction. As a result, the body attaches chemicals to insulin-binding proteins that enhance their activity.
Tea's insulin-boosting activity also might explain why tea seems to help prevent heart disease and high blood pressure, Anderson said. Medical investigators think high blood sugar damages blood vessels, and increasing insulin activity lowers blood sugar levels.
"This work seems to be truly new and extremely exciting," biochemist Anne-Marie Roussel at the Universite Joseph Fourier in Grenoble, France, told UPI. "This work is well done, and the data is promising not only to treat diabetes but perhaps also in preventing it." Roussel and Anderson added more tea studies need to be conducted with patients, not in lab models.
The scientists described their findings in a report published online by the Journal of Agricultural and Food Chemistry.
(Reported by Charles Choi, UPI Science News, in New York)
Copyright: Copyright 2002 by United Press International.
---------------------------------------------------------------------------------
By K.L. CAPOZZA, UPI Science News
SAN FRANCISCO, Mar 24, 2003 (United Press International via COMTEX) -- Long touted for its health-promoting properties, green tea might be an effective treatment for acne, a study suggests.
Green tea has been shown to fight bacteria, reduce inflammation and decrease hormone activity -- three characteristics that make the ancient tea an excellent candidate for an acne therapy.
"This study showed that 3 percent green tea cream is comparable to 4 percent benzoyl peroxide in the treatment of moderate to severe acne," said lead author, Dr. Jennifer Gan-Wong, with the Memorial Medical Center in the Philippines.
Gan-Wong presented her team's findings at the American Academy of Dermatology Annual Meeting. Researchers from tested the promising candidate -- in the form of a 3 percent green tea extract cream -- vs. the leading treatment for acne, 4 percent benzoyl peroxide cream.
A computer randomized a group of 108 subjects into one of two treatment groups. One applied benzoyl peroxide cream twice daily for 12 weeks and the other used green tea extract cream twice daily for the same period. Patients received identical bottles of cream and were unaware of the type of treatment they were assigned.
Subjects were examined and photographed each week by dermatologists, who also were unaware which treatment each patient had been given.
The researchers noted the green tea cream seemed to lighten patients' skin color and improve the overall appearance of their complexion.
Green tea therapy might be appealing to consumers because conventional wisdom holds that natural products are less toxic and have fewer side effects than other drug products, the researchers said.
The preliminary data suggest green tea extract cream causes fewer side effects than benzoyl peroxide treatment. Patients in the green tea group reported fewer cases of dry skin, itching and allergic responses.
The findings, while promising, are not yet substantial enough to change clinical practice, Dr. Azucena Arguelles, a private practice dermatologist from Mountain View, Calif., told United Press International.
"My sense is that for this to be out on the market and adopted by the medical community the results will need to be repeated," she said.
The finding could be relevant to the millions of Americans who suffer from acne breakouts, a condition which affects nearly 85 percent of the U.S. population and has a detrimental affect on self-esteem and well-being
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Green tea extract and aromatase activity
Green tea extract has been found to inhibit aromatase activity in male rats. (Aromatase is an enzyme that converts androgens to estrogens.) A recent study administered green tea extract catechins to male rats for two, four and eight weeks, starting at age five weeks. It was found that a 5% dose to male rats for two to eight weeks induced goiters and decreased weights of the body, testis and prostate gland. The treatment elevated circulating thyroid stimulating hormone (TSH), luteinizing hormone (LH) and testosterone levels, and decreased tri-iodothyronine and thyroxine levels (hormones secreted by the thymus gland). Green tea exhibited inhibitory effects on human placental aromatase activity. The endocrinological changes in the body were anti-thyroid effects and aromatase inhibition due to the effects of green tea extract and its components.
FOOD AND CHEMICAL TOXICOLOGY, 2002, Vol 40, Iss 7, pp 925-933
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Green tea benefits digestive tract
Tea catechins undergo various metabolic changes after they are taken orally, though a large percentage is excreted intact with the feces. Epidemiological studies suggest a protective effect of tea against various human cancers, including colon and rectum. The bactericidal property of tea catechins plays several roles in the digestive tract. In the small intestine, catechins inhibit alpha-amylase activity, and a certain amount is absorbed into the portal vein. Although catechins are bactericidal, they do not affect lactic acid bacteria. Including tea catechins in the diet for several weeks decreases putrefactive products and increases organic acids by lowering pH. These changes were achieved with 100 mg of tea catechins (equivalent to two to five cups of green tea) three times daily with meals for three weeks. When catechin administration ceased, the effects reversed after one week. Catechins should be considered further in colon carcinogenesis studies.
JOURNAL OF CELLULAR BIOCHEMISTRY, 1997, Suppl. 27, pp 52-58
The inhibitory action of tea polyphenols towards the development and growth of bacterial spores was examined. The heat resistance of B stearothermophilus spores (a thermophilic spore-forming bacterium) was reduced by the addition of tea polyphenols. Clostridium thermoaceticum, an anaerobic spore-forming bacterium, also exhibited reduced heat resistance of its spores in the presence of tea polyphenols. Epigallocatechin gallate, the main component of tea polyphenols, showed strong activity against both B stearothermophilus and C thermoaceticum. The heat resistance of these bacterial spores was more rapidly decreased by the addition of tea polyphenols at high temperatures.
JOURNAL OF BIOSCIENCE AND BIOENGINEERING, 2000, Vol 90, Iss 1, pp 81-85
Green tea protects against alcohol-induced liver injury
A study examined the antioxidant polyphenolic extract of green tea against early alcohol-induced liver injury. Rats were fed high-fat liquid diets with or without alcohol and green tea (300 mg kg/day) continuously for four weeks. After four weeks, the blood ALT (sign of liver damage) levels were increased significantly from 35 to 114 (four-fold over placebo group values). However, the inclusion of green tea extract in the diet significantly blunted the increase to 65. The alcohol also caused severe fatty accumulation, mild inflammation and tissue death in the liver. However, with green tea extract, the increase in tissue death caused by alcohol were significantly reduced, while not affecting fat accumulation or inflammation. Alcohol also significantly increased the accumulation of protein adducts (products of lipid peroxidation and an indication of oxidative stress). However, green tea extract blocked this effect almost completely. Green tea extract also blunted the increase of TNFalpha (causes inflammation) protein levels in the liver by alcohol. The results indicate that dietary antioxidants, such as those found in green tea, prevent early alcohol-induced liver injury, most likely by preventing free radical stress.
BIOLOGICAL CHEMISTRY 2002;383(3-4):663-70
Green tea, grape juice, and colon cancer
Full source: BIOLOGICAL & PHARMACEUTICAL BULLETIN, 2000, Vol 23, Iss 6, pp 695-699
A study reported the effects of tea and juice on the activity of the intestines. Green tea strongly inhibited the E. coli-expressed mouse intestinal phenol sulfotransferases (P-STs) activity in vitro. The active component of green tea, (-)-Epigallocatechin gallate (EGCG), was found to be the most potent inhibitor among the catechins tested. (-)EGCG also inhibited the P-ST activity of the human colon cancer cells. Among fruit juices examined (apple, grape, grapefruit and orange), grape juice exhibited the most potent inhibitory action on the P-ST activity of mouse intestines and human colon cancer cells. The inhibitory activity of grape juice was located mainly in the skin and seeds. Flavonols, such as quercetin and kaempferol, inhibited the P-ST activity at low concentrations. The results suggest the possible inhibition of P-ST activity in human intestines by green tea or grape juice.
Curr Med Chem Anti-Canc Agents 2002 Jul;2(4):441-63 Related Articles, Links
Green tea catechins as novel antitumor and antiangiogenic compounds.
Demeule M, Michaud-Levesque J, Annabi B, Gingras D, Boivin D, Jodoin J, Lamy S, Bertrand Y, Beliveau R.
Laboratoire de Medecine Moleculaire, UQAM-Hocric;pital Sainte-Justine, Montreal, Canada. [email protected]
The concept of cancer prevention by use of naturally occuring substances that could be included in the diet is under investigation as a practical approach towards reducing cancer incidence, and therefore the mortality and morbidity associated with this disease. Tea, which is the most popularly consumed beverage aside from water, has been particularly associated with decreased risk of various proliferative diseases such as cancer and atherosclerosis in humans. Various studies have provided evidence that polyphenols are the strongest biologically active agents in green tea. Green tea polyphenols (GTPs) mainly consist of catechins (3-flavanols), of which (-)-epigallocatechin gallate is the most abundant and the most extensively studied. Recent observations have raised the possibility that green tea catechins, in addition to their antioxidative properties, also affect the molecular mechanisms involved in angiogenesis, extracellular matrix degradation, regulation of cell death and multidrug resistance. This article will review the effects and the biological activities of green tea catechins in relation to these mechanisms, each of which plays a crucial role in the development of cancer in humans. The extraction of polyphenols from green tea, as well as their bioavailability, are also discussed since these two important parameters affect blood and tissue levels of the GTPs and consequently their biological activities. In addition, general perspectives on the application of dietary GTPs as novel antiangiogenic and antitumor compounds are also presented.
PMID: 12678730 [PubMed - in process]
Kidney Int 2003 May;63(5):1785-1790 Related Articles, Links
Effect of green tea extract on cardiac hypertrophy following 5/6 nephrectomy in the rat.
Priyadarshi S, Valentine B, Han C, Fedorova OV, Bagrov AY, Liu J, Periyasamy SM, Kennedy D, Malhotra D, Xie Z, Shapiro JI.
The Departments of Medicine and Pharmacology Medical College of Ohio, Toledo, Ohio; The Institute of Nutrition and Food Hygiene, Chinese Academy of Preventive Medical Sciences, Beijing, China; and Laboratory of Cardiovascular Science,National Institute on Aging, National Institutes of Health, Baltimore, Maryland.
Effect of green tea extract on cardiac hypertrophy following 5/6 nephrectomy in the rat. BACKGROUND: Left ventricular hypertrophy commonly complicates chronic renal failure. We have observed that at least one pathway of left ventricular hypertrophy appears to involve signaling through reactive oxygen species (ROS). Green tea is a substance that appears to have substantial antioxidant activity, yet is safe and is currently widely used. We, therefore, studied whether green tea supplementation could attenuate the development of left ventricular hypertrophy in an animal model of chronic renal failure. METHODS: Male Sprague-Dawley rats were subjected to sham or remnant kidney surgery and given green tea extract (0.1% and 0.25%) or plain drinking water for the next 4 weeks. Heart weight, body weight, and cardiac Na-K-ATPase activity were measured at the end of this period. To further test our hypothesis, we performed studies in cardiac myocytes isolated from adult male Sprague-Dawley rats. We measured the generation of ROS using the oxidant sensitive dye dichlorofluorescein (DCF) as well as (3H)phenylalanine incorporation following exposure to cardiac glycosides with and without green tea extract. RESULTS: Administration of green tea extract at 0.25% resulted in attenuation of left ventricular hypertrophy, hypertension, and preserved cardiac Na-K-ATPase activity in rats subjected to remnant kidney surgery (all P < 0.01). In subsequent studies performed in isolated cardiac myocytes, both ouabain and marinobu***enin (MBG) were both found to increase ROS production and (3H)phenylalanine incorporation at concentrations substantially below their inhibitor concentration (IC) 50 for the sodium pump. Addition of green tea extract prevented increases in ROS production as well as (3H)phenylalanine incorporation in these isolated cardiac myocytes. CONCLUSION: Green tea extract appears to block the development of cardiac hypertrophy in experimental renal failure. Some of this effect may be related to the attenuation of hypertension, but a direct effect on cardiac myocyte ROS production and growth was also identified. Clinical studies of green tea extract in chronic renal failure patients may be warranted.
PMID: 12675854 [PubMed - as supplied by publisher]
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To Freshen Breath
In the first study, conducted at Pace University, green tea extracts were mixed with several different kinds of bacteria, including those that cause strep throat and tooth decay. The researchers found that green tea was effective at fighting bacteria by inhibiting their growth.
"Our research shows tea extracts can destroy the organism that causes disease," says lead researcher Milton Schiffenbauer, PhD, a microbiologist and biology professor at Pace University in New York City, in a news release.
In fact, the same study suggests that green tea boosts the effectiveness of toothpaste and mouthwash in fighting viruses. Toothpaste and mouthwash had very little virus-fighting effect when mixed with bacteria; however, when green tea extract was added, 99% to 100% of the bacteria disappeared.
What's responsible for the health benefits of tea? Teas contain polyphenols, which are antioxidants that protect human cells from damage. Flavonids are a group of polyphenols that occur naturally in tea. It is suspected that high levels of these polyphenols in the body can fight viruses as well as cancer, including pancreas, colon, bladder, prostate, and breast cancer.
In the "bad breath" study, researchers combined black tea extracts with three species of bacteria (all linked with bad breath) in petri dishes for 48 hours. They compared the results with bacteria that sat alone.
In all cases, tea polyphenols inhibited the growth of bacteria by 30% and reduced the production of compounds that cause bad breath.
The study suggests that rinsing with black tea keeps plaque from forming and destroys acids that cause tooth decay.
"Besides inhibiting the growth of pathogens in the mouth, black tea and its polyphenols may benefit human oral health by suppressing the bad-smelling compounds that these pathogens produce," says lead researcher Christine D. Wu, PhD, professor of periodontics at the University of Illinois, Chicago, in a news release.
Both studies detailing health benefits of tea were presented at the annual American Society for Microbiology General Meeting held in Washington, D.C., this week
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Mechanism found for green tea in cancer fight
In research conducted at H. Lee Moffitt Cancer Center & Research Institute in Tampa Florida, a mechanism of green tea polyphenols' ability to cause the death of cancer cells was elucidated. By testing green tea polyphenols effect on prostate cancer cell lines, varying concentrations of the polyphenols were found to diminish a protein called Bcl-XL which protects cancer cells from apoptosis, which is programmed cell death.
Green tea has been shown to prevent several types of cancer in animal models. Human populations who consume green tea have lower rates of stomach, liver, pancreatic, breast, lung, esophageal and skin cancers.
Aslamuzzaman Kazi, PhD, research fellow in the Drug Discovery Program at Moffitt Cancer Center, described the finding: "The higher the concentration, the better the response - meaning more apoptosis, or programming that tells cells to die -- apparently occurring as a result of a greater decrease in Bcl-XL, a protein that protects cancer cells from apoptosis. At all concentrations, response was apparent within three hours."
Pin Dou, PhD, associate professor of oncology, biochemistry, and molecular biology at Moffitt further explained, "Because Bcl-XL is overexpressed in many cancers, it could be a key target in all these cancers and explain why green tea polyphenols (are) able to prevent human cancers in mouse models . . . Data from our laboratory suggests that at least one enzyme may modify Bcl-XL and that it is the actual target of tea. We also want to see if that target is present in all human cancers or just some of them."
Green tea has been shown to lower "bad" LDL cholesterol and serum triglyceride levels. Further, green tea's potent antioxidant effects inhibit the oxidation of LDL cholesterol in the arteries, which plays a major contributory role in the formation of atherosclerosis. "There is considerable epidemiological evidence that tea drinking lowers the risk of heart disease" (FEBS Lett., Aug. 1998, 433(1-2):44-46).
The cholesterol-lowering (hypocholesterolemic) effects of green tea (as well as black tea) have been confirmed by both animal and human epidemiological studies. High consumption of green tea by humans, especially more than 10 cups a day, was found to be associated with higher HDLs and lower LDL and VLDL cholesterol, as well as with various biomarkers indicating better liver health. Lower levels of lipid peroxides in the liver are one well-confirmed benefit of green-tea supplementation found in study after study.
A Japanese study relates, "Green tea catechin acts to limit the excessive rise in blood cholesterol" based on a series of studies reported in 1996 (Journal Nutritional Science Vitaminol., 32:613).
Additionally, some very exciting results were found when rats were fed 2.5% green tea leaves in their diet. The experimental group showed a drop in total cholesterol, low-density cholesterol, and triglycerides. The body weight of green tea-fed rats was 10 to 18% lower than that of rats not consuming green tea. In addition, the activity of antioxidant enzymes superoxide dismutase (SOD) and catalase, and of anticarcinogenic phase-II enzyme glutathione S-transferase (GST), were significantly higher in the green tea group, as was the glutathione level in the liver. There was no liver or kidney toxicity. Thus, the study demonstrated combined cardiovascular and anticancer effects of green tea.
The relation between green tea consumption and serum lipid concentrations were examined using cross-sectional data on 1306 males in Japan. Results indicated that total cholesterol levels were found to be inversely related to the consumption of green tea. "Adjusted mean concentrations of total cholesterol were significantly lower in men drinking nine cups or more a day than in those consuming zero to two cups a day" (Prev. Med. July 1992, 21(4):526-31). No wonder the Japanese people have the longest life span. Most Japanese sip tea all day long.
Green tea also has been shown to elevate levels of HDL, the good cholesterol that helps remove atherosclerotic plaque from arterial walls. Green tea is a natural ACE inhibitor. This is an extra benefit for those with high cholesterol and blood pressure, as published studies show lowered blood pressure in animals and humans given green tea extracts. We recommend one capsule (350 mg) of green tea 95% extract daily, or drinking one to ten cups of green or black tea a day
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Calorie burning properties:
A study has found: "Subjects spent 24 hours in a respiratory chamber designed to measure the rate calories were burned and energy expenditure. Those receiving the green tea experienced what researchers consider a significant increase in both tests. Tea extract subjects burned 4 percent more calories, and overall energy expenditure rose 4.5 percent."
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BELTSVILLE, Md., Oct 10, 2002 (United Press International via COMTEX) -- Common tea can be an effective weapon in the fight against diabetes because it boosts insulin activity in the body by more than 15-fold, scientists at the U.S. Department of Agriculture said Thursday.
Insulin problems lie at the root of the potentially fatal illness diabetes, so researchers hope tea-based treatments will help treat or prevent the disease, which affects 17 million Americans. Not only that, this insulin-boosting phenomenon may explain why tea can help fight heart disease and high blood pressure as well.
"This is just one of the many well-established benefits that tea may have," researcher Richard Anderson, a biochemist at the USDA's Beltsville Human Nutrition Research Center in Maryland, told United Press International.
Tea has a long history as a folk remedy for diabetes in China, the West Indies and central Africa. Over the past 20 years scientists also have uncovered potential benefits from tea against cancer, high blood pressure and infection.
"Tea wasn't the only factor we looked at, but it was the best," Anderson said.
Anderson and his colleague Marilyn Polansky analyzed a host of herbs, spices and plants for any beneficial effect involving insulin, the hormone the body needs to convert sugar into energy. They took fat cells from rats and grew them in test tubes because fat cells are highly sensitive to insulin, Anderson explained. Then, they gave the cells mildly radioactive sugar, insulin, and various tea extracts. The radioactive sugar is easy to track and the more the extracts aided insulin activity, the more sugar the cells would convert.
The scientists found black, green and oolong teas boosted insulin activity the most. This insulin-augmenting effect was seen with both caffeinated and non-caffeinated teas, but not with herbal teas, which do not use leaves from tea bushes.
They also identified tea's most insulin-enhancing chemical, called epigallocatechin gallate. Adding whole or skim milk, nondairy creamers or soy milk appears to soak up tea's insulin-augmenting compounds and inhibit the insulin boost, although these milky sponges may release the tea extracts in the stomach, Anderson said. No absorption problem was seen with lemon juice.
"Hopefully people can get better simply by drinking tea," Anderson said. "These compounds clear from the body quite quickly, some in less than six hours, some less than four. The effects are not going to be that large, so you're going to need to continue drinking tea."
Anderson said his team also found cinnamon showed similar insulin-enhancing power. He suggests tea and cinnamon affects the cell proteins insulin binds to.
Diabetes is a disease where the body either does not make insulin or does not properly use it when it does produce it. The scientists think tea increases the body's sensitivity to insulin by setting off a chain reaction. As a result, the body attaches chemicals to insulin-binding proteins that enhance their activity.
Tea's insulin-boosting activity also might explain why tea seems to help prevent heart disease and high blood pressure, Anderson said. Medical investigators think high blood sugar damages blood vessels, and increasing insulin activity lowers blood sugar levels.
"This work seems to be truly new and extremely exciting," biochemist Anne-Marie Roussel at the Universite Joseph Fourier in Grenoble, France, told UPI. "This work is well done, and the data is promising not only to treat diabetes but perhaps also in preventing it." Roussel and Anderson added more tea studies need to be conducted with patients, not in lab models.
The scientists described their findings in a report published online by the Journal of Agricultural and Food Chemistry.
(Reported by Charles Choi, UPI Science News, in New York)
Copyright: Copyright 2002 by United Press International.
---------------------------------------------------------------------------------
By K.L. CAPOZZA, UPI Science News
SAN FRANCISCO, Mar 24, 2003 (United Press International via COMTEX) -- Long touted for its health-promoting properties, green tea might be an effective treatment for acne, a study suggests.
Green tea has been shown to fight bacteria, reduce inflammation and decrease hormone activity -- three characteristics that make the ancient tea an excellent candidate for an acne therapy.
"This study showed that 3 percent green tea cream is comparable to 4 percent benzoyl peroxide in the treatment of moderate to severe acne," said lead author, Dr. Jennifer Gan-Wong, with the Memorial Medical Center in the Philippines.
Gan-Wong presented her team's findings at the American Academy of Dermatology Annual Meeting. Researchers from tested the promising candidate -- in the form of a 3 percent green tea extract cream -- vs. the leading treatment for acne, 4 percent benzoyl peroxide cream.
A computer randomized a group of 108 subjects into one of two treatment groups. One applied benzoyl peroxide cream twice daily for 12 weeks and the other used green tea extract cream twice daily for the same period. Patients received identical bottles of cream and were unaware of the type of treatment they were assigned.
Subjects were examined and photographed each week by dermatologists, who also were unaware which treatment each patient had been given.
The researchers noted the green tea cream seemed to lighten patients' skin color and improve the overall appearance of their complexion.
Green tea therapy might be appealing to consumers because conventional wisdom holds that natural products are less toxic and have fewer side effects than other drug products, the researchers said.
The preliminary data suggest green tea extract cream causes fewer side effects than benzoyl peroxide treatment. Patients in the green tea group reported fewer cases of dry skin, itching and allergic responses.
The findings, while promising, are not yet substantial enough to change clinical practice, Dr. Azucena Arguelles, a private practice dermatologist from Mountain View, Calif., told United Press International.
"My sense is that for this to be out on the market and adopted by the medical community the results will need to be repeated," she said.
The finding could be relevant to the millions of Americans who suffer from acne breakouts, a condition which affects nearly 85 percent of the U.S. population and has a detrimental affect on self-esteem and well-being
------------------------------------------------------------------------------
Green tea extract and aromatase activity
Green tea extract has been found to inhibit aromatase activity in male rats. (Aromatase is an enzyme that converts androgens to estrogens.) A recent study administered green tea extract catechins to male rats for two, four and eight weeks, starting at age five weeks. It was found that a 5% dose to male rats for two to eight weeks induced goiters and decreased weights of the body, testis and prostate gland. The treatment elevated circulating thyroid stimulating hormone (TSH), luteinizing hormone (LH) and testosterone levels, and decreased tri-iodothyronine and thyroxine levels (hormones secreted by the thymus gland). Green tea exhibited inhibitory effects on human placental aromatase activity. The endocrinological changes in the body were anti-thyroid effects and aromatase inhibition due to the effects of green tea extract and its components.
FOOD AND CHEMICAL TOXICOLOGY, 2002, Vol 40, Iss 7, pp 925-933
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Green tea benefits digestive tract
Tea catechins undergo various metabolic changes after they are taken orally, though a large percentage is excreted intact with the feces. Epidemiological studies suggest a protective effect of tea against various human cancers, including colon and rectum. The bactericidal property of tea catechins plays several roles in the digestive tract. In the small intestine, catechins inhibit alpha-amylase activity, and a certain amount is absorbed into the portal vein. Although catechins are bactericidal, they do not affect lactic acid bacteria. Including tea catechins in the diet for several weeks decreases putrefactive products and increases organic acids by lowering pH. These changes were achieved with 100 mg of tea catechins (equivalent to two to five cups of green tea) three times daily with meals for three weeks. When catechin administration ceased, the effects reversed after one week. Catechins should be considered further in colon carcinogenesis studies.
JOURNAL OF CELLULAR BIOCHEMISTRY, 1997, Suppl. 27, pp 52-58
The inhibitory action of tea polyphenols towards the development and growth of bacterial spores was examined. The heat resistance of B stearothermophilus spores (a thermophilic spore-forming bacterium) was reduced by the addition of tea polyphenols. Clostridium thermoaceticum, an anaerobic spore-forming bacterium, also exhibited reduced heat resistance of its spores in the presence of tea polyphenols. Epigallocatechin gallate, the main component of tea polyphenols, showed strong activity against both B stearothermophilus and C thermoaceticum. The heat resistance of these bacterial spores was more rapidly decreased by the addition of tea polyphenols at high temperatures.
JOURNAL OF BIOSCIENCE AND BIOENGINEERING, 2000, Vol 90, Iss 1, pp 81-85
Green tea protects against alcohol-induced liver injury
A study examined the antioxidant polyphenolic extract of green tea against early alcohol-induced liver injury. Rats were fed high-fat liquid diets with or without alcohol and green tea (300 mg kg/day) continuously for four weeks. After four weeks, the blood ALT (sign of liver damage) levels were increased significantly from 35 to 114 (four-fold over placebo group values). However, the inclusion of green tea extract in the diet significantly blunted the increase to 65. The alcohol also caused severe fatty accumulation, mild inflammation and tissue death in the liver. However, with green tea extract, the increase in tissue death caused by alcohol were significantly reduced, while not affecting fat accumulation or inflammation. Alcohol also significantly increased the accumulation of protein adducts (products of lipid peroxidation and an indication of oxidative stress). However, green tea extract blocked this effect almost completely. Green tea extract also blunted the increase of TNFalpha (causes inflammation) protein levels in the liver by alcohol. The results indicate that dietary antioxidants, such as those found in green tea, prevent early alcohol-induced liver injury, most likely by preventing free radical stress.
BIOLOGICAL CHEMISTRY 2002;383(3-4):663-70
Green tea, grape juice, and colon cancer
Full source: BIOLOGICAL & PHARMACEUTICAL BULLETIN, 2000, Vol 23, Iss 6, pp 695-699
A study reported the effects of tea and juice on the activity of the intestines. Green tea strongly inhibited the E. coli-expressed mouse intestinal phenol sulfotransferases (P-STs) activity in vitro. The active component of green tea, (-)-Epigallocatechin gallate (EGCG), was found to be the most potent inhibitor among the catechins tested. (-)EGCG also inhibited the P-ST activity of the human colon cancer cells. Among fruit juices examined (apple, grape, grapefruit and orange), grape juice exhibited the most potent inhibitory action on the P-ST activity of mouse intestines and human colon cancer cells. The inhibitory activity of grape juice was located mainly in the skin and seeds. Flavonols, such as quercetin and kaempferol, inhibited the P-ST activity at low concentrations. The results suggest the possible inhibition of P-ST activity in human intestines by green tea or grape juice.
Curr Med Chem Anti-Canc Agents 2002 Jul;2(4):441-63 Related Articles, Links
Green tea catechins as novel antitumor and antiangiogenic compounds.
Demeule M, Michaud-Levesque J, Annabi B, Gingras D, Boivin D, Jodoin J, Lamy S, Bertrand Y, Beliveau R.
Laboratoire de Medecine Moleculaire, UQAM-Hocric;pital Sainte-Justine, Montreal, Canada. [email protected]
The concept of cancer prevention by use of naturally occuring substances that could be included in the diet is under investigation as a practical approach towards reducing cancer incidence, and therefore the mortality and morbidity associated with this disease. Tea, which is the most popularly consumed beverage aside from water, has been particularly associated with decreased risk of various proliferative diseases such as cancer and atherosclerosis in humans. Various studies have provided evidence that polyphenols are the strongest biologically active agents in green tea. Green tea polyphenols (GTPs) mainly consist of catechins (3-flavanols), of which (-)-epigallocatechin gallate is the most abundant and the most extensively studied. Recent observations have raised the possibility that green tea catechins, in addition to their antioxidative properties, also affect the molecular mechanisms involved in angiogenesis, extracellular matrix degradation, regulation of cell death and multidrug resistance. This article will review the effects and the biological activities of green tea catechins in relation to these mechanisms, each of which plays a crucial role in the development of cancer in humans. The extraction of polyphenols from green tea, as well as their bioavailability, are also discussed since these two important parameters affect blood and tissue levels of the GTPs and consequently their biological activities. In addition, general perspectives on the application of dietary GTPs as novel antiangiogenic and antitumor compounds are also presented.
PMID: 12678730 [PubMed - in process]
Kidney Int 2003 May;63(5):1785-1790 Related Articles, Links
Effect of green tea extract on cardiac hypertrophy following 5/6 nephrectomy in the rat.
Priyadarshi S, Valentine B, Han C, Fedorova OV, Bagrov AY, Liu J, Periyasamy SM, Kennedy D, Malhotra D, Xie Z, Shapiro JI.
The Departments of Medicine and Pharmacology Medical College of Ohio, Toledo, Ohio; The Institute of Nutrition and Food Hygiene, Chinese Academy of Preventive Medical Sciences, Beijing, China; and Laboratory of Cardiovascular Science,National Institute on Aging, National Institutes of Health, Baltimore, Maryland.
Effect of green tea extract on cardiac hypertrophy following 5/6 nephrectomy in the rat. BACKGROUND: Left ventricular hypertrophy commonly complicates chronic renal failure. We have observed that at least one pathway of left ventricular hypertrophy appears to involve signaling through reactive oxygen species (ROS). Green tea is a substance that appears to have substantial antioxidant activity, yet is safe and is currently widely used. We, therefore, studied whether green tea supplementation could attenuate the development of left ventricular hypertrophy in an animal model of chronic renal failure. METHODS: Male Sprague-Dawley rats were subjected to sham or remnant kidney surgery and given green tea extract (0.1% and 0.25%) or plain drinking water for the next 4 weeks. Heart weight, body weight, and cardiac Na-K-ATPase activity were measured at the end of this period. To further test our hypothesis, we performed studies in cardiac myocytes isolated from adult male Sprague-Dawley rats. We measured the generation of ROS using the oxidant sensitive dye dichlorofluorescein (DCF) as well as (3H)phenylalanine incorporation following exposure to cardiac glycosides with and without green tea extract. RESULTS: Administration of green tea extract at 0.25% resulted in attenuation of left ventricular hypertrophy, hypertension, and preserved cardiac Na-K-ATPase activity in rats subjected to remnant kidney surgery (all P < 0.01). In subsequent studies performed in isolated cardiac myocytes, both ouabain and marinobu***enin (MBG) were both found to increase ROS production and (3H)phenylalanine incorporation at concentrations substantially below their inhibitor concentration (IC) 50 for the sodium pump. Addition of green tea extract prevented increases in ROS production as well as (3H)phenylalanine incorporation in these isolated cardiac myocytes. CONCLUSION: Green tea extract appears to block the development of cardiac hypertrophy in experimental renal failure. Some of this effect may be related to the attenuation of hypertension, but a direct effect on cardiac myocyte ROS production and growth was also identified. Clinical studies of green tea extract in chronic renal failure patients may be warranted.
PMID: 12675854 [PubMed - as supplied by publisher]
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To Freshen Breath
In the first study, conducted at Pace University, green tea extracts were mixed with several different kinds of bacteria, including those that cause strep throat and tooth decay. The researchers found that green tea was effective at fighting bacteria by inhibiting their growth.
"Our research shows tea extracts can destroy the organism that causes disease," says lead researcher Milton Schiffenbauer, PhD, a microbiologist and biology professor at Pace University in New York City, in a news release.
In fact, the same study suggests that green tea boosts the effectiveness of toothpaste and mouthwash in fighting viruses. Toothpaste and mouthwash had very little virus-fighting effect when mixed with bacteria; however, when green tea extract was added, 99% to 100% of the bacteria disappeared.
What's responsible for the health benefits of tea? Teas contain polyphenols, which are antioxidants that protect human cells from damage. Flavonids are a group of polyphenols that occur naturally in tea. It is suspected that high levels of these polyphenols in the body can fight viruses as well as cancer, including pancreas, colon, bladder, prostate, and breast cancer.
In the "bad breath" study, researchers combined black tea extracts with three species of bacteria (all linked with bad breath) in petri dishes for 48 hours. They compared the results with bacteria that sat alone.
In all cases, tea polyphenols inhibited the growth of bacteria by 30% and reduced the production of compounds that cause bad breath.
The study suggests that rinsing with black tea keeps plaque from forming and destroys acids that cause tooth decay.
"Besides inhibiting the growth of pathogens in the mouth, black tea and its polyphenols may benefit human oral health by suppressing the bad-smelling compounds that these pathogens produce," says lead researcher Christine D. Wu, PhD, professor of periodontics at the University of Illinois, Chicago, in a news release.
Both studies detailing health benefits of tea were presented at the annual American Society for Microbiology General Meeting held in Washington, D.C., this week
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