Wednesday, December 28, 2011

Green tea prevents reinfection in Hepatitis C liver transplants

A flavonoid found in green tea—inhibits the hepatitis C virus (HCV) from entering liver cells, according to German researchers. The flavonoid, epigallocatechin-3-gallate (EGCG), may offer an antiviral strategy to prevent HCV reinfection following liver transplantation.

HCV infection can lead to chronic hepatitis, cirrhosis, and hepatocellular carcinoma (HCC) or primary liver cancer. HCV is one of the most common causes of chronic liver disease and a primary indication for liver transplantation, affecting up to 170 million individuals worldwide according to estimates from the World Health Organization (WHO). Prior studies report that nearly 2% of the world population is infected with chronic HCV and up to 20% of the population in some countries.
While standard treatment with interferon with ribavirin and newer protease inhibitors may clear infection in some individuals, a substantial number of patients still may not respond to these therapies. For individuals receiving liver transplants due to complications from HCV, reinfection of the healthy donor liver remains a significant concern. Antiviral strategies that target HCV in its early stages are urgently needed to prevent graft 
reinfection and improve long-term outcomes for patients.
To address this critical issue, Dr. Sandra Ciesek and Dr. Eike Steinmann from the Hannover Medical School in Germany investigated the effect of the EGCG molecule, which is a major component of green tea, in preventing HCV from attaching to liver cells. "Green tea catechins such as EGCG and its derivatives epigallocatechin (EGC), epicatechingallate (ECG), and epicatechin (EC) have been shown to exhibit antiviral and anti-oncogenic properties," explains Dr. Ciesek. "Our study further explores the potential effect these flavonoids have in preventing HCV reinfection following liver transplantation."

Results showed that unlike its derivatives, EGCG inhibits entry of HCV into liver cells. The authors suggest that EGCG may impede HCV cell entry by acting on the host cell as the green tea catechin was not found to alter the density of virus particles. Pretreatment of cells with EGCG before HCV inoculation did not reduce the infection; however application during inoculation inhibited the rapid spread of the HCV. Lastly, researchers showed that EGCG inhibits viral attachment—the initial step in the HCV infection process. "The green tea antioxidant EGCG inhibits HCV cell entry by blocking viral attachment and may offer a new approach to prevent HCV infection, particularly reinfection following liver transplantation." concludes Dr. Ciesek.

by VR Sreeraman on  December 02, 2011

Monday, December 26, 2011

The Science of brewing tea

The Chinese attach great importance to water for a good brew. Since ancient times, "The tea of Longjing (Dragon Well) and the water of Hupao (Tiger Running S pring)," and "The water from the midstream of the Yangtze River and the tea from the top of Mount Mengshan" have been regarded as the best pairs for making tea. It is generally believed that "water is the mother of tea," and that it takes the incorporation of the right leaves and the right water to fully bring out the potential flavor of tea.
The second rule is that tea wares are also of great importance to the quality of tea. Different teas should go with different types of tea wares. People generally tend to steep gteen tea in glasses, oolong tea in kungfu tea in kungfu tea vessels, and red tea in purple clay pots. The utensil called gaiwan, literally "lidded bowl," is what the northern Chinese prefer when it comes to steeping scented tea.
One must first be equipped with an understanding of the characteristics of all types of tea. The inherent character of tea will be able to be fully released if scientific methods are applied. In general, the three most impotant things one should bear in mind are the proportion of leaves to water, the water temperature and the period of steeping.
By Explore Cultural China

Green tea and obesity

Green tea has recently become the latest weapon in the war on weight. But does it really work? The results of some new studies are promising, indicating that green tea can increase the rate of calorie burning, reduce body fat levels and even prevent excess weight gain. And although most tests have been performed on laboratory animals, at least one with humans showed that taking in the equivalent of 3 cups of green tea per day helped the body burn a significant amount of additional calories.
*        A 1999 study published in the American Journal of Clinical Nutrition looked at the effects of green tea extract on energy "burning" in humans.1 Men who took daily doses of green tea extract containing EGCg plus caffeine in an amount equivalent to that found in about 3 cups of green tea, burned about 80 more calories per day than those who didn’t take the extract. (Just taking caffeine without EGCg didn’t have the same effect.) And while 80 calories per day may not seem like much, over the course of a year that adds up to 29,200 calories, or a little more than 8 pounds lost – without making any other changes!
*      In a study involving animals, green tea extract actually helped prevent obesity. Two groups of mice were placed on a high-fat diet designed to ensure weight gain. At the same time, one group received green tea extract while the other did not. The mice that were given green tea extract ended up gaining 47% less weight than those who didn’t get the extract.2 
*      In another animal study, green tea extract actually helped to reverse established obesity. In a 2005 study published in the Annals of Nutrition and Metabolism, rats were deliberately overfed to make them obese. Then they were given supplemental EGCg, which markedly decreased the amount of fat tissue in their bodies, reversing their obesity.3 
Why would green tea make a difference in the amount of fatty tissue one carries? The EGCg contained in the tea is believed to rev up the fat-burning effects of brown fat, send glucose to muscle tissue where it is more likely to be burned (rather than to fat tissue, where it’s more likely to be stored), and inhibit the action of fat-digesting enzymes, so that ingested fat is less likely to be broken down and absorbed by the body.

Dulloo AG, Duret C, Rohrer D, et al. Efficacy of a green tea extract rich in catechin polyphenols and caffeine in increasing 24-h energy expenditure and fat oxidation in humans. Am J Clin Nutr 1999;70(6):1040-50.
Shimotoyodome A, Haramizu S, Inaba M, et al. Exercise and green tea extract stimulate fat oxidation and prevent obesity in mice. Med Sci Sports Exerc 2005;37(11):1884-92.
Wolfram S, Raederstorff D, Wang Y, et al. TEAVIGO (epigallocatechin gallate) supplementation prevents obesity in rodents by reducing adipose tissue mass. Ann Nutr Metab 2005;49(1):54-63. Epub 2005 Feb 25.

Wednesday, December 21, 2011

Drinking tea makes your mouth clean

Asians have long been in the habit of drinking tea after eating meals or sweets, and scientific research shows that this makes sense. Dental caries (cavities) are the result of bacteria called S. mutans, which use sugars in the mouth to produce a sticky substance called plaque. The plaque coats the teeth and gives the bacteria something to cling to, so more and more bacteria can gather. And while they’re producing plaque, the S. mutans bacteria also produce an unfortunate byproduct called lactic acid, which eats into the tooth enamel. This combination of plaque buildup and lactic acid is responsible for the decay that occurs in our nearly indestructible tooth enamel.

Research has shown that green tea catechins can help fight tooth decay in several ways: by making it harder for the bacteria to cling to the teeth, inhibiting the production of plaque, and destroying some of the S. mutans bacteria -- and these effects can occur with as little as one cup of green tea!
In addition, a recent study published in Caries Research has found that green tea’s EGCg helps reduce the ability of S. mutans to produce the enamel-destroying acid. In this study, volunteers either rinsed their mouths with an EGCg solution or with plain water, then rinsed their mouths again 30 minutes later with a sucrose solution to give S. mutans something to work on. Later, plaque samples were taken and the acidity of the samples was measured.
When the volunteers had pre-rinsed with the EGCg solution, the acidity of the plaque was significantly lower than it was when they had pre-rinsed with plain water. Less acid means less tooth decay. So having a cup of green tea after you eat that candy bar might not be a bad idea…

Monday, December 19, 2011

Bringing down the sugar

Elevated blood glucose can devastate the body, causing heart disease, stroke, kidney failure, nerve damage, gangrene (especially of the feet) and blindness. And while drinking green tea has been associated with a decrease in the absorption of carbohydrate and a reduced risk of developing type 2 diabetes, it’s still uncertain whether or not tea drinking can actually lower blood glucose.  
To find out, researchers gathered dietary information (including consumption of black or green tea) from 300 elderly men and women living in the Mediterranean area. They also measured their fasting blood glucose levels, body mass index (BMI) and other factors. 
The results? Tea intake was associated with lower blood glucose levels, but only in non-obese people. And moderate tea consumption (1-2 cups per day) reduced the risk of having diabetes by 88%, no matter what the participant’s age, sex, dietary and exercise habits, or smoking status -- but again, only in the non-obese.

(Polychronopoulos E, Zeimbekis A, Kastorini CM, et al. Effects of black and green tea consumption on blood glucose levels in non-obese elderly men and women from Mediterranean Islands (MEDIS epidemiological study). Eur J Nutr 2008;47(1):10-6.)

Saturday, December 17, 2011

Green tea and skin toxicity

Skin toxicity is a common side effect of radiation for solid tumors. Besides damaged skin, radiation that leads to skin toxicity can cause gaps in treatment while the skin heals. Researchers from UCLA and the University of Freiburg, Germany wanted to find out if green and black tea extracts, with their anti-inflammatory properties, could protect against skin toxicity and reduce its duration. 
The volunteers, 60 patients with cancer of the head and neck or pelvic region, were given topical skin treatments of green or black tea extracts before radiation. The tea extracts, which in “test tube” studies reduced the release of pro-inflammatory cytokines, decreased the duration of skin toxicity after radiation by 5-10 days in the cancer patients. These effects were seen with both green and black tea extracts, although green tea extract was more effective. 

Friday, December 16, 2011

Puer tea and diabetes

A sip of Pu'er tea can be as helpful as drugs in lowering blood sugar and preventing diabetes, says a recent press briefing by the Pu'er city government. That is the finding of scientists at Jilin University and the Changchun Science and Technology University, after two years of studies organized by Pu'er city, Yunnan province.
The provincial government's Science and Technology Department also organized a forum for health experts to discuss the health benefits of Pu'er.
"Owing to Pu'er tea's obvious effect in restraining some enzymes related to diabetes, the experts believe drinking the right amounts of Pu'er tea can help lower blood sugar levels and prevent diabetes to some extent," says Sheng Jun, deputy mayor of Pu'er city.

The first phase of the study involved 20 genetically obese lab rats with very high blood sugar levels. Researchers fed 10 of them with regular amounts of mature Pu'er tea while the other 10 rats were not given any.
"Only two rats of the group not fed any tea, survived after 11 months. The others became infected and had sores before dying," says Sheng. "Meanwhile, all the 10 rats that drank Pu'er tea survived, and showed no trace of sores or infection."
The research team also compared Pu'er tea with Rosiglitazone, a widely used medicine to lower blood sugar levels. After two weeks, they found that the rats that were fed Rosiglitazone had 36.5 percent less blood sugar, while the figure was 42 percent for the group that was fed Pu'er tea. Also, those on puer lost weight while those on the drug showed no evidence of any weight loss.
The researchers carried out a test among 120 diabetic volunteers. They were asked to drink Pu'er regularly and stop their medicines, while making no change to their dietary habits. Seventy percent reported blood sugar levels lowered to below 7 mmol/L, with an average decrease of 35 percent.
Although all teas are believed to be capable of lowering blood sugar levels, Pu'er and oolong are thought to be the most effective. In fact, they sometimes lower blood sugar level so fast that some people feel weak in the limbs, experience a faster heartbeat and even feel dizzy - all signs of too low a blood sugar level. The Chinese refer to such people as zui cha, or tea drunk.
Sheng Jun reveals that Yunnan has one of China's best longevity rates and attributes this to tea drinking. "Moreover, as Yunnan has the lowest incidence of cancer, Pu'er city has the lowest number of cancer patients in Yunnan."
The city has applied for a patent for its research into the health benefits of Pu'er, and will continue with its tests.

Article by Explore Cultural China

Wednesday, December 14, 2011

Green Tea - Bacteria Killer

One of the amazing effects of tea polyphenols is their ability to destroy pathogenic (disease-causing) bacteria like E. coli, Salmonella, Staphylococcus aureus and Clostridium inside the body, particularly in the digestive tract. But if tea polyphenols are strong enough to kill major pathogens, do they also kill the “friendly” bacteria in your intestinal tract – the ones you need to digest and absorb your food properly?
To find out, scientists from the National University of Singapore looked at the effects of different tea polyphenols extracted from Yunnan Chinese tea on the growth of 28 kinds of bacteria, both “friendly” and pathogenic, found in the intestines.  
As expected, the polyphenols inhibited the growth of pathogenic bacteria, especially Clostridium perfringens (a common cause of food poisoning), Clostridium difficile (linked to colitis), and Bacteroides (a cause of abscesses if the bacteria manage to escape from the intestines). However the gut’s “friendly” bacteria, including Bifidobacterium and Lactobacillus, were relatively unaffected by the tea polyphenols.
In short, tea was able to increase the "friendly" bacteria while decreasing the "unfriendly" bacteria, thus changing the balance of bacteria in the gut for the better. 

(Lee HC, Jenner AM, Low CS, Lee YK. Effect of tea phenolics and their aromatic fecal bacterial metabolites on intestinal microbiota. Research in Microbiology 2006;157(9):876-84.

Thursday, December 8, 2011

Brewing Up the Latest Tea Research

Leaves from the plant Camellia sinensis are processed three different ways to produce the three major classes of tea, known as black (left), green (center), and oolong.
Tea is the most-consumed beverage worldwide next to water. For some 5,000 years, people have been getting a lift from brewing tea leaves. But it's only been in the last three decades that researchers have immersed themselves in the science behind tea's purported health benefits.

Several ARS scientists at various laboratories are studying the bioactivity of tea compounds. Some have studied the relationship between tea and metabolism, and some have looked at the effect of tea on blood glucose and cholesterol levels. Others are studying tea's impact on the ability of the body's cells to handle oxidative stress. And some are looking at the effect of green tea on slowing development of abnormal blood vessels in lab mice. In certain diseases, including cancer, angiogenesis—growth of new blood vessels—becomes excessive. These new vessels not only provide nourishment to tumors, but they also serve as portals through which tumor cells can escape into the body's circulatory system and spread to other organs. Compounds found to be anti-angiogenic may prove therapeutic by "starving" the tumors.

Differences in Tea Types
The age-old Camellia sinensis plant is the source of all nonherbal teas. Manufacturers process C. sinensis leaves three different ways to produce the three major classes of teas known as green, black, and oolong. Today, about 75 percent of the tea produced worldwide is black; about 23 percent is green; and about 2 percent is oolong.

Next to water, tea is the most consumed beverage worldwide. The source of all non herbal teas is Camellia sinensi. (K10695-2)   
Consider that coffee beans are green before roasting turns them brown and ready for market. Tea leaves are also green at harvest. To achieve a variety of taste profiles, manufacturers carefully control whether, and for how long, tea leaves are exposed to air, a process called fermentation. When fermentation is completely arrested, the tea stays "green" or yellowish brown. When fermentation time is long, the leaves darken and become "black" tea. Somewhere in between these two extremes, "oolong" tea is created.
Over the centuries, as C. sinensis plants grew in the sun, they protected themselves against photosynthetic stressors by forming chemicals known as polyphenols. This group of beneficial compounds includes flavonoids—the same class of compounds that give many fruits and vegetables their antioxidant boost. It is perhaps because of tea's high antioxidant activity that tea research is taking such a variety of turns.

The Metabolics of Tea
Physiologist William Rumpler is investigating the ancient Chinese belief that oolong tea is effective in controlling body weight. Rumpler is with ARS' Diet and Human Performance Laboratory (DHPL), one of seven laboratories that make up the Beltsville Human Nutrition Research Center (BHNRC), Beltsville, Maryland.
To measure how tea influences energy expenditure (EE), Rumpler and colleagues gave each of 12 male volunteers 4 separate beverage formulas for 3 consecutive days. Before the study, the volunteers refrained from consuming caffeine and had their 24-hour EE measured. EE was measured again on the third day of each formula treatment. The treatments consisted of full-strength tea, colored water with caffeine equal to full-strength tea, half-strength tea, and colored water.
The results showed that the EE of volunteers was about 3 percent higher after they drank either the caffeinated water or the full-strength tea than after they drank the colored water. On average, the volunteers burned an additional 67 calories a day when they drank tea instead of an equal amount of water. Perhaps most interesting was that fat oxidation was a significant 12 percent higher after the full-strength tea treatment than after the water treatment.
"Our data suggested that a component of tea other than caffeine might have promoted preferential use of fat as an energy source," says Beverly Clevidence, a study coauthor and head of the DHPL. "But the information is tentative, and we need more studies to confirm it," she adds.  
It is universally accepted that caffeinated tea raises metabolic rate because caffeine is a stimulant. "The interesting part of our study, which agreed with findings from a similar study in England, was that when you drink tea you turn on the fat-burning spigot a little bit more than when you drink caffeinated water," says Rumpler. Some scientists speculate that caffeine and EGCG—a highly active catechin in tea—may act together to increase fat oxidation.
"Anecdotal evidence over time, particularly in China, points to a relationship between green tea consumption and weight loss," says Rumpler. "But until we do a really comprehensive study in which we have humans drink tea and see whether they lose weight, we can't actually say that green tea makes people lose weight. What we can say is that it raises metabolic rates and increases fat oxidation rates. Those are two things that are predictive of weight loss."
Coping with Confounding Variables
In September 2002, ARS and other researchers met at the U.S. Department of Agriculture in Washington, D.C., for the Third International Scientific Symposium on Tea and Human Health. The symposium was hosted by organizer Jeffrey B. Blumberg, associate director of the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University in Boston, Massachusetts. Blumberg is also director of HNRCA's Antioxidants Research Laboratory.
One issue discussed there was inconsistency among early studies of tea. "Confounding"—a situation in which findings are affected by a variety of uncontrolled factors—can occur. "Some studies are simply not sensitive enough to eliminate confounding factors," says ARS chemist Joseph T. Judd, who is with DHPL. In the case of tea studies, it could be as simple as a volunteer's getting the same flavonoids that are in tea from other foods consumed during the study.
Blumberg notes that flavonoid concentrations differ in tea beverages, depending on whether the preparation was blended, decaffeinated, brewed, or iced. Milk protein, for example, when added to tea, had previously been reported to possibly bind to, and therefore reduce, the flavonoid concentrations.
"There has been only one study that showed that adding milk decreased the bioavailability of catechins in tea," says Blumberg. "Those results were not replicated in any of several subsequent studies." Many factors can affect the way tea compounds are absorbed, metabolized, and excreted, according to Blumberg.
A Low-Down on Lipids
Judd, who is with the DHPL, is the lead author of a recent study that found that drinking tea lowered cholesterol and, therefore, could possibly reduce the risk of coronary heart disease (CHD). Judd points out that while several epidemiological studies found that green and black tea consumption is associated with reduced risk of CHD, experimental studies had not confirmed this. "The experimental studies did not control the background diet of the volunteers," says Judd. "Other foods or nutrients consumed during the studies could very well have affected the risk factors."
Judd's recent study assessed the effects of black tea consumption on blood lipid and lipoprotein concentrations in adults with mildly high cholesterol. He carefully controlled the volunteers' diet and weight. Seven men and eight women were given five servings of black tea a day for 3 weeks and a tea-flavored water for another 3-week period. In a third study period, caffeine was added to the tea-flavored water in an amount similar to that found in the tea.
"Overall, we found a 6 to 10 percent lowering of blood lipids in drinkers of black tea in just 3 weeks," says Judd. What's more, the study showed no effect on high-density lipoprotein, or "good," cholesterol.
The study's authors concluded that drinking black tea—along with following a prudent diet moderately low in fat, cholesterol, and saturated fatty acids—reduces total and LDL cholesterol by significant amounts and may, therefore, reduce the risk of CHD. The study is slated to appear in an upcoming issue of the Journal of Nutrition that will feature the tea symposium proceedings and an introduction by Blumberg.
Judd is now conducting a study on the antioxidant effects of tea phytonutrients on smokers.
Enhancing Insulin Activity
ARS chemist Richard Anderson found that regularly brewed tea, when added to the fat cells of laboratory rats, increased insulin activity by more than 15 times. Anderson is with the BHNRC's Nutrient Requirements and Functions Laboratory. He noted that this increased insulin activity was found with green, black, and oolong teas, regardless of whether caffeinated or decaffeinated.
Further, his research showed that in green and oolong teas, the catechin EGCG was largely responsible for the results. In black tea, active ingredients included tannins and theaflavins, in addition to EGCG. "The amount we tested was comparatively very small, considering the effect we observed," says Anderson. Confirmational studies in humans are required before the results can be applied to people.
Ernst J. Schaefer, director of the HNRCA's Lipid Metabolism Laboratory, recently completed a pilot study during which 8 volunteers with type II diabetes had lower blood sugar levels by 15 to 20 percent after drinking 6 cups of tea per day for 8 weeks. Schaefer and Blumberg have since launched a 24-week, randomized, double-blind study involving 40 male and female volunteers with type II diabetes, not taking insulin. "We want to examine the effect that green and black teas have on the glucose levels of the volunteers," says Schaefer.
Topping the Flavonoid Charts
Since nearly 95 percent of tea's polyphenol compounds are flavonoids, tea ranks among plants with the highest total flavonoid content. Green tea contains more simple flavonoids, called catechins, while black tea contains more complex varieties, called thearubigins and theaflavins. Some polyphenols have recently been determined—in test tube studies—to be more potent antioxidants than the well-known vitamins A, C, and E. But results from such test tube, or in vitro, tests cannot be applied to humans because they do not account for factors such as bioavailability, metabolism, and excretion, says Blumberg.
"We know that these flavonoids are not as bioavailable as vitamin C on a per-milligram basis," says Paul E. Milbury, a scientist with the Boston HNRCA's Antioxidants Research Laboratory. Still, one 6-ounce cup (about 173 grams) of green tea has about 235 milligrams of catechins, whereas a medium-large (178 grams) apple has 16 milligrams of catechins and 10 milligrams of vitamin C. This data is available from the BHNRC's Flavonoid and National Nutrient databases.
Up to 90 percent of tea consumed in the United States is black. But green tea consumption has more than doubled recently. "Over the last 4 years, green tea consumption increased tremendously, going from 3 to 4 percent of total tea consumed in the United States to about 9 percent today," says Joe Simrany, president of the New York City-based Tea Council of the U.S.A. Simrany says the council is seeking a standardized system for measuring and labeling commercial teas' antioxidants.
Blumberg says consuming a variety of tea types and preparations adds nutritional benefits to the diet. "The beauty of tea is that it can be enjoyed in so many ways, depending on individual tastes and preferences," he says. "My hope is that future studies will be designed to accurately assess tea's polyphenol levels and to measure tea's role in lowering the risk of chronic diseases."—By Rosalie Marion Bliss, Agricultural Research Service Information Staff.

This research is part of Human Nutrition, an ARS National Program (#107) described on the World Wide Web at
To reach scientists mentioned in this article, contact Rosalie Bliss, USDA-ARS Information Staff, 5601 Sunnyside Ave., Beltsville, MD 20705-5129; phone (301) 504-4318, fax (301) 504-1641.
"Brewing Up the Latest Tea Research" was published in the September 2003 issue of Agricultural Research magazine.

Wednesday, December 7, 2011

Green Tea - an overview

Botanical evidence indicates that India and China were among the first countries to cultivate tea. Today, tea is the most widely consumed beverage in the world, second only to water. Hundreds of millions of people drink tea around the world, and studies suggest that green tea (Camellia sinesis) in particular has many health benefits.

There are three main varieties of tea -- green, black, and oolong. The difference between the teas is in their processing. Green tea is made from unfermented leaves and reportedly contains the highest concentration of powerful antioxidants called polyphenols. Antioxidants are substances that scavenge free radicals -- damaging compounds in the body that alter cells, tamper with DNA (genetic material), and even cause cell death. Free radicals occur naturally in the body, but environmental toxins (including ultraviolet rays from the sun, radiation, cigarette smoke, and air pollution) also give rise to these damaging particles. Many scientists believe that free radicals contribute to the aging process as well as the development of a number of health problems, including cancer and heart disease. Antioxidants such as polyphenols in green tea can neutralize free radicals and may reduce or even help prevent some of the damage they cause.

Green tea has been consumed throughout the ages in India, China, Japan, and Thailand. In traditional Chinese and Indian medicine, practitioners used green tea as a stimulant, diuretic (to promote the excretion of urine), astringent (to control bleeding and help heal wounds), and to improve heart health. Other traditional uses of green tea include treating flatulence (gas), regulating body temperature and blood sugar, promoting digestion, and improving mental processes.

Green tea has been extensively studied in people, animals, and laboratory experiments. Results from these studies suggest that green tea may be useful for the following health conditions:


Population-based clinical studies indicate that the antioxidant properties of green tea may help prevent atherosclerosis, particularly coronary artery disease. (Population-based studies means studies that follow large groups of people over time or studies that are comparing groups of people living in different cultures or with different dietary habits.) Researchers aren't sure why green tea reduces the risk of heart disease by lowering cholesterol and triglyceride levels. Studies show that black tea has similar beneficial effects. In fact, researchers estimate that the rate of heart attack decreases by 11% with consumption of 3 cups of tea per day. In May 2006, however, the U.S. Food and Drug Administration (FDA) rejected a petition from teamakers to allow tea labels to claim that green tea reduces the risk of heart disease. The FDA concluded that there is no credible evidence to support qualified health claims for green tea or green tea extract reducing the risk of heart disease.

High cholesterol

Research shows that green tea lowers total cholesterol and raises HDL ("good") cholesterol in both animals and people. One population-based clinical study found that men who drink green tea are more likely to have lower total cholesterol than those who do not drink green tea. Results from one animal study suggest that polyphenols in green tea may block the intestinal absorption of cholesterol and promote its excretion from the body. In another small study of male smokers, researchers found that green tea significantly reduced blood levels of harmful LDL cholesterol.


Several population-based clinical studies have shown that both green and black teas help protect against cancer. For example, cancer rates tend to be low in countries such as Japan where people regularly consume green tea. However, it is not possible to determine from these population-based studies whether green tea actually prevents cancer in people. Emerging clinical studies suggest that the polyphenols in tea, especially green tea, may play an important role in the prevention of cancer. Researchers also believe that polyphenols help kill cancerous cells and stop their progression.

Bladder cancer. Only a few clinical studies have examined the relationship between bladder cancer and 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 clinical 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.

Breast cancer. Clinical studies in animals and test tubes suggest that polyphenols in green tea inhibit the growth of breast cancer cells. In one study of 472 women with various stages of breast cancer, researchers found that women who consumed the most green tea experienced the least spread of cancer (particularly premenopausal women in the early stages of breast cancer). They also found that women with early stages of the disease who drank at least 5 cups of tea every day before being diagnosed with cancer were less likely to suffer recurrences of the disease after completion of treatment. However, women with late stages of breast cancer experienced little or no improvement from drinking green tea. In terms of breast cancer prevention, the studies are inconclusive. In one very large study, researchers found that drinking tea, green or any other type, was not associated with a reduced risk of breast cancer. However, when the researchers broke down the sample by age, among women under the age of 50, those who consumed 3 or more cups of tea per day were 37% less likely to develop breast cancer compared to women who didn't drink tea.

Ovarian cancer. In a clinical 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. Other studies found no beneficial effects.

Colorectal cancer. Clinical studies on the effects of green tea on colon or rectal cancer have produced conflicting results. Some clinical studies show decreased risk in those who drink the tea, while others show increased risk. In one study, women who drank 5 or more cups of green tea per day had a significantly lower risk of colorectal cancer compared to non-tea-drinkers. There was no effect in men, however. Other studies show that regular tea consumption may reduce the risk of colorectal cancer in women. Further research is needed before researchers can recommend green tea for the prevention of colorectal cancer.

Esophageal cancer. Studies in laboratory animals have found that green tea polyphenols inhibit the growth of esophageal cancer cells. However, clinical studies in people have produced conflicting findings. For example, one large-scale population-based clinical study found that green tea offered significant protection against the development of esophageal cancer (particularly among women). Another population-based clinical study revealed just the opposite -- green tea consumption was associated with an increased risk of esophageal cancer. In fact, the stronger and hotter the tea, the greater the risk. Given these conflicting results, further research is needed before scientists can recommend green tea for the prevention of esophageal cancer.

Lung cancer. While green tea polyphenols have been shown to inhibit the growth of human lung cancer cells in test tubes, few clinicial studies have investigated the link between green tea consumption and lung cancer in people and even these studies have been conflicting. One population-based clinical study found that Okinawan tea (similar to green tea but partially fermented) was associated with decreased lung cancer risk, particularly among women. A second clinical study revealed that green tea and black tea significantly increased the risk of lung cancer. As with colon and esophageal cancers, further clinical studies are needed before researchers can draw any conclusions about green tea and lung cancer.

Pancreatic cancer. In one large-scale clinical 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.

Prostate cancer. Laboratory studies have found that green tea extracts prevent the growth of prostate cancer cells in test tubes. In a large clinical study conducted in Southeast China researchers found that the risk of prostate cancer declined with increasing frequency, duration and quantity of green tea consumption. However, both green and black tea extracts also stimulated genes that cause cells to be less sensitive to chemotherapy drugs. Given this potential interaction, people should not drink black and green tea (as well as extracts of these teas) while receiving chemotherapy.

Skin cancer. The main polyphenol in green tea is epigallocatechin gallate (EGCG). Scientific studies suggest that EGCG and green tea polyphenols have anti-inflammatory and anticancer properties that may help prevent the onset and growth of skin tumors.

Stomach cancer. Laboratory studies have found that green tea polyphenols inhibit the growth of stomach cancer cells in test tubes, but clinical 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 clinicial study including more than 26,000 men and women in Japan found no association between green tea consumption and stomach cancer risk. Some clinicial studies even suggest that green tea may increase the risk of stomach cancer.

Further clinicial studies are underway to determine whether green tea helps reduce the risk of stomach cancer. Although green tea is considered safe for people at risk for stomach cancer, it is too soon to tell whether green tea reduces the likelihood of developing this disease.

Inflammatory Bowel Disease (IBD)

Green tea may help reduce inflammation associated with Crohn's disease and ulcerative colitis, the two types of IBD. If green tea proves to be helpful for preventing colon cancer, this would be an added benefit for those with IBD because they are at risk for colon cancer.


Green tea has been used traditionally to control blood sugar in the body. Animal studies suggest that green tea may help prevent the development of type 1 diabetes and slow the progression once it has developed. People with type 1 diabetes produce little or no insulin, a hormone that converts glucose (sugar), starches, and other foods into energy needed for daily life. Green tea may help regulate glucose in the body.

A few small clinical studies have found that daily supplementation of the diet with green tea extract powder lowered the hemoglobin A1c level in individuals with borderline diabetes.

Liver disease

Population-based clinical studies have shown that men who drink more than 10 cups of green tea per day are less likely to develop disorders of the liver. Green tea also seems to protect the liver from the damaging effects of toxic substances such as alcohol. Animal studies have shown that green tea helps protect against the development of liver tumors in mice.

Results from several animal and human studies suggest that one of the polyphenols present in green tea, known as catechin, may help treat viral hepatitis (inflammation of the liver from a virus). In these studies, catechin was isolated from green tea and used in very high concentrations. It is not clear whether green tea (which contains a lower concentration of catechins) confers these same benefits to people with hepatitis.

Weight loss

Clinical studies suggest that green tea extract may boost metabolism and help burn fat. One study confirmed that the combination of green tea and caffeine improved weight loss and maintenance in overweight and moderately obese individuals. Some researchers speculate that substances in green tea known as polyphenols, specifically the catechins, are responsible for the herb's fat-burning effect.

Other uses

Drinking green tea has been found effective in a small clinical study for dental caries, or tooth decay. More studies need to be performed. Green tea may also be useful in inflammatory diseases, such as arthritis. Research indicates that green tea may benefit arthritis by reducing inflammation and slowing cartilage breakdown. Chemicals found in green tea may also be effective in treating genital warts and preventing symptoms of colds and influenza. Studies also show that drinking green tea is associated with reduced risk of all cause mortality.

Plant Description:

Green, black, and oolong tea are all derived from the leaves of the Camellia sinensis plant. Originally cultivated in East Asia, this plant grows as large as a shrub or tree. Today, Camellia sinensis grows throughout Asia and parts of the Middle East and Africa.

People in Asian countries more commonly consume green and oolong tea while black tea is most popular in the United States. Green tea is prepared from unfermented leaves, the leaves of oolong tea are partially fermented, and black tea is fully fermented. The more the leaves are fermented, the lower the polyphenol content (See: "What's It Made Of?") and the higher the caffeine content. Green tea has the highest polyphenol content while black tea has roughly 2 - 3 times the caffeine content of green tea.

What's It Made Of?:

The healthful properties of green tea are largely attributed to polyphenols, chemicals with potent antioxidant properties. In fact, the antioxidant effects of polyphenols appear to be greater than vitamin C. The polyphenols in green tea also give it a somewhat bitter flavor.

Polyphenols contained in teas are classified as catechins. Green tea contains six primary catechin compounds: catechin, gallaogatechin, epicatechin, epigallocatechin, epicatechin gallate, and apigallocatechin gallate (also known as EGCG). EGCG is the most studied polyphenol component in green tea and the most active.

Green tea also contains alkaloids including caffeine, theobromine, and theophylline. These alkaloids provide green tea's stimulant effects. L-theanine, an amino acid compound found in green tea, has been studied for its calming effects on the nervous system.

Available Forms:

Most green tea dietary supplements are sold as dried leaf tea in capsule form. Standardized extracts of green tea are preferred. There are also liquid extracts made from the leaves and leaf buds. The average cup of green tea contains between 50 - 150 mg polyphenols (antioxidants). Decaffeinated green tea products contain concentrated polyphenols. Caffeine-free supplements are available.

How to Take It:


There are no known scientific reports on the pediatric use of green tea, so it is not recommended for children.


Depending on the brand, 2 - 3 cups of green tea per day (for a total of 240 - 320 mg polyphenols) or 100 - 750 mg per day of standardized green tea extract is recommended. Caffeine-free products are available and recommended.


The use of herbs is a time-honored approach to strengthening the body and treating disease. However, herbs contain active substances that can trigger side effects and interact with other herbs, supplements, or medications. For these reasons, people should take herbs with care, under the supervision of a practitioner knowledgeable in the field of botanical medicine.

People with heart problems, kidney disorders, stomach ulcers, and psychological disorders (particularly anxiety) should not take green tea. Pregnant and breastfeeding women should also avoid green tea.

People who drink excessive amounts of caffeine (including caffeine from green tea) for prolonged periods of time may experience irritability, insomnia, heart palpitations, and dizziness. Caffeine overdose can cause nausea, vomiting, diarrhea, headaches, and loss of appetite. If you are drinking a lot of tea and start to vomit or have abdominal spasms, you may have caffeine poisoning. If your symptoms are severe, lower your caffeine intake and see your health care provider.

Possible Interactions:

If you are being treated with any of the following medications, you should not drink green tea or take green tea extract without first talking to your health care provider:

Adenosine -- Green tea may inhibit the actions of adenosine, a medication given in the hospital for an irregular (and usually unstable) heart rhythm.

Antibiotics, Beta-lactam -- Green tea may increase the effectiveness of beta-lactam antibiotics by reducing bacterial resistance to treatment.

Benzodiazepines -- Caffeine (including caffeine from green tea) has been shown to reduce the sedative effects of benzodiazepines (medications commonly used to treat anxiety, such as diazepam and lorazepam).

Beta-blockers, Propranolol, and Metoprolol -- Caffeine (including caffeine from green tea) may increase blood pressure in people taking propranolol and metoprolol (medications used to treat high blood pressure and heart disease).

Blood Thinning Medications (Including Aspirin) -- People who take warfarin, a blood thinning medication, should not drink green tea. Since green tea contains vitamin K, it can make warfarin ineffective. Meanwhile, you should not mix green tea and aspirin because they both prevent platelets from clotting. Using the two together may increase your risk of bleeding.

Chemotherapy -- The combination of green tea and chemotherapy medications, specifically doxorubicin and tamoxifen, increased the effectiveness of these medications in laboratory tests. However, these results have not yet been demonstrated in studies on people. On the other hand, there have been reports of both green and black tea extracts stimulating a gene in prostate cancer cells that may cause them to be less sensitive to chemotherapy drugs. Given this potential interaction, people should not drink black and green tea (as well as extracts of these teas) while receiving chemotherapy for prostate cancer in particular.

Clozapine -- The antipsychotic effects of the medication clozapine may be reduced if taken fewer than 40 minutes after drinking green tea.

Ephedrine -- When taken together with ephedrine, green tea may cause agitation, tremors, insomnia, and weight loss.

Lithium -- Green tea has been shown to reduce blood levels of lithium (a medication used to treat manic/depression).

Monoamine Oxidase Inhibitors (MAOIs) -- Green tea may cause a severe increase in blood pressure (called a "hypertensive crisis") when taken together with MAOIs, which are used to treat depression. Examples of MAOIs include phenelzine and tranylcypromine.

Oral Contraceptives -- Oral contraceptives can prolong the amount of time caffeine stays in the body and may increase its stimulating effects.

Phenylpropanolamine -- A combination of caffeine (including caffeine from green tea) and phenylpropanolamine (an ingredient used in many over-the-counter and prescription cough and cold medications and weight loss products) can cause mania and a severe increase in blood pressure. The FDA issued a public health advisory in November 2000 to warn people of the risk of bleeding in the brain from use of this medication and has strongly urged all manufacturers of this drug to remove it from the market.

Alternative Names:

Camellia sinensis

Reviewed last on: 9/20/2010
A.D.A.M. Editorial Team: David Zieve, MD, MHA, and David R. Eltz. Previously reviewed by Steven D. Ehrlich, NMD, Solutions Acupuncture, a private practice specializing in complementary and alternative medicine, Phoenix, AZ. Review provided by VeriMed Healthcare Network (8/24/2009).
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Tuesday, December 6, 2011

Study: Green tea may trim "bad" cholesterol

(Reuters) - Green tea, taken in a capsule or drunk in a cup, may shave a few points off "bad" cholesterol readings, according to a U.S. study involving more than a thousand people.

The findings, published in the Journal of the American Dietetic Association, showed that green tea trimmed 5 to 6 points more from people's total cholesterol and "bad" LDL cholesterol levels than dummy capsules or other treatments.

The trials tested either green tea itself or capsules containing green-tea compounds called catechins, which are thought to decrease cholesterol absorption in the gut.

Green tea in a cup was more consistently effective than capsules, though the benefits overall were fairly small, noted senior researcher Olivia Phung, an assistant professor of pharmacy at Western University of Health Sciences in Pomona, California.

"If someone is already taking medication for their cholesterol, they should stick with it and not try to trade it for green tea, either capsules or the beverage," she told Reuters Health in an email.

But adding green tea to your diet could be one way to further improve cholesterol numbers, she said.

The researchers, however, found no strong evidence that green tea boosted "good" HDL cholesterol, or cut triglycerides, another type of blood fat.

Phung's team pooled the results of 20 clinical trials that involved a total of 1,415 adults.

Participants were randomly assigned to either use green tea every day, as a beverage or capsule, or be part of "control" groups that took placebo capsules, drank a low-catechin tea or downed water.

The trials lasted anywhere from three weeks to six months and the benefits seemed to be limited to people who already had high cholesterol when they entered the study.

Overall, tea seemed more effective than capsules, though Phung said there isn't enough data to be sure that the beverage is better than the extract.

A number of clinical trials that examined whether green tea, or its extracts, can benefit people's cholesterol levels have reached mixed conclusions. Most of the trials have been small, making them less reliable.

There are other questions too, including what dose of green tea catechins is ideal.

In the trials Phung's team studied, the researchers were unable to test for a "dose-response" effect, which would have shown whether the cholesterol benefits increase as the catechin dose goes up.

"We would really need to have some head-to-head studies comparing the different forms of green tea in order to show which ones work more effectively," Phung said.

As for side effects, green tea is considered safe in moderate amounts, though the drink and the extracts contain caffeine, which some people may need to avoid.

There have also been a few dozen cases of liver damage reported among people using green tea extracts, but it's not certain that the supplements are to blame. SOURCE:

(Reporting from New York by Amy Norton at Reuters Health; editing by Elaine Lies and Idayu Suparto)

Monday, December 5, 2011

On love and hot beverages

Sunday, December 4, 2011

Tea, Truth and Beauty

If man has no tea in him, he is incapable of understanding truth and beauty. 
                                                       ~Japanese Proverb

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