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Lately, green tea has been touted as an elixir for a myriad of illnesses, including heart disease and cancer. However, a researcher from Rutgers University says that while preliminary data point to tea’s curative powers in animals, nothing has been proven in humans. In fact, writes Chung S. Yang, PhD, in an editorial column in the November/December issue of the journal Nutrition, “if such beneficial effects do exist in humans, they are likely to be mild.”
Tea has been a popular beverage for centuries in countries like China, Japan, India, and England. In fact, tea consumption in the world ranks second only to water consumption. Recently, the United States has experienced a surge in tea drinking. But tea’s unique flavor is not the only reason consumers are increasing their tea consumption. Recent research has shown that tea may protect against several types of cancer, it may reduce the risk of heart disease and stroke, and it has greater antioxidant power than many fruits and vegetables. That is, if you drink a lot of it.
The three basic tea types come from the evergreen shrub Camellia sinensis. Black, green, and oolong teas are produced from the tea plant by varying the processing conditions. Black tea is produced by fermenting the leaves, while green tea leaves are not fermented. Oolong teas go through a shorter fermentation period than black teas and are regarded as semi-fermented. All three kinds go through a heating process to halt fermentation.
Although most people drink black tea (made from fermented leaves), about a quarter of all tea consumed is green (unfermented). All teas from Camellia sinensis contain compounds known as polyphenols -- a class of bioflavonoids -- which are found in all plants. Polyphenols have anti-cancer, antioxidant, anti-bacterial, and anti-viral properties. Besides tea, these compounds are especially high in coffee, red grapes, kidney beans, raisins, prunes, and red wine.
It is believed that green tea guards against cancer by scavenging for free radicals, which are the by-products from all the chemical reactions that occur in the body -- like the exhaust from an automobile. Free radicals can damage the cells that block the action of cancer-causing agents, or carcinogens, and detoxify them. Tea polyphenols also may limit cell replication, the primary characteristic of cancer.
In one widely publicized study, researchers at the Case Western Reserve University School of Medicine, in Cleveland, reported that an ingredient in the polyphenols in green tea kills cancer cells while sparing healthy cells. In the study, reported in the Dec. 17, 1997, issue of the Journal of the National Cancer Institute, the researchers tested this ingredient, EGCG, on cancerous human and mouse cells of the skin, lymph system, and prostate and on normal human skin cells. They found that EGCG caused cell death in cancer cells while leaving healthy cells unharmed.
Purdue University (West Lafayette, Ind.) researchers Dorothy Morre and D. James Morre reported in December 1998 at the 38th annual meeting of the American Society for Cell Biology in San Francisco, that EGCG inhibits an enzyme called NOX. This enzyme helps carry out several cell functions and is required for growth in both normal and cancerous cells. The overactive and cancer-causing form of NOX is known as tNOX.
“Our research shows that green tea leaves are rich in this anti-cancer compound, with concentrations high enough to induce anti-cancer effects in the body,” Dorothy Morre, professor of foods and nutrition in Purdue’s School of Consumer and Family Sciences, tells WebMD. “Drinking more than four cups of green tea a day,” she says, “could provide enough of the active compound to slow and prevent the growth of cancer cells. Granted, for most people that’s a lot of tea.”
There have been other studies on tea’s effect on heart disease. As Yang points out, these studies show that tea polyphenols inhibit the oxidation of LDL, the “bad” cholesterol.
No one is saying, yet, that drinking green tea cures cancer or heart disease in humans. In fact, in testing tea’s effects, researchers have used a strong concentration -- about 100 times what the Lipton Company estimates is in one cup of tea. More laboratory research plus human studies are needed to see whether extracts of green tea can be effective as drugs to prevent cancer and stop prostate and other tumors from growing.
Yang says that if in fact tea does, people would need to slurp 3-10 cups a day for maximum protection from common forms of cancer. He says this in itself may be harmful. “Ingestion of large amounts of tea may cause nutritional and other problems because of the caffeine and the strong binding activities of tea polyphenols,” notes Yang, who is with the Laboratory for Cancer Research at Rutgers University, in Piscataway, N.J.
Elizabeth Kaegi, MB, reporting in 1998 on behalf of the Task Force on Alternative Therapies of the Canadian Breast Cancer Research Initiative, says that while she believes moderate consumption of green tea appears safe, “because excess caffeine can cause nervousness, insomnia, and irregularities in heart rate, pregnant women, nursing mothers, and patients with cardiac problems are usually advised to limit their intake to two cups.” Kaegi is the former director of Medical Affairs and Cancer Control at the National Cancer Institute of Canada and the Canadian Cancer Society.
Although research has shown that tea may protect against diseases such as heart disease and cancer, nothing has been proven in humans. Tea contains polyphenols, which exhibit antioxidant, anti-cancer, anti-bacterial, and anti-viral properties, but a person would have to consume several cups per day to reap the benefits. Drinking large quantities of tea, however, may not be so healthy, because the caffeine content could cause nervousness, insomnia, and heart rate irregularities.
LONDON — Green tea could help prevent cancer through the action of a chemical known as a cathechin, researchers in the United States reported Wednesday.
They said it was non-toxic in doses found in tea — but a single cup of green tea contained huge amounts of the chemical.
“One of the major ingredients of green tea inhibits urokinase, an enzyme crucial for cancer growth,” Jerzy Jankun of the Medical College of Ohio in Toledo and colleagues wrote in a letter to the science journal Nature.
Researchers knew tea and especially green tea contained chemicals that could protect against cancer but have been unable to identify the precise mechanism.
Jankun’s group said they had found epigallocathechin-3 gallate (EGCG) acted against urokinase, which is often found in large amounts in human cancers. EGCG attaches to it and prevents it from invading cells and forming tumors.
“Inhibition of urokinase can decrease tumour size or even cause complete remission of cancers in mice,” Jankun’s group wrote.
Black tea — the type drunk most often in the West — does not work in this way because the brewing process destroys the effects of the cathechins.
Jankun’s group compared the dose of cathechins in green tea to a drug, amiloride, that acts in a similar way but is usually used to treat high blood pressure and congestive heart failure.
“Amiloride is administered in a maximum dose of 20 mg per day, whereas a single cup of tea contains 150 mg (of) EGCG, and some tea lovers consume up to 10 cups a day,” they wrote.
“Such high levels of a urokinase inhibitor are likely to have a physiological effect and could reduce incidence of cancer in humans or the size of cancers already formed.”
Few people drink as much tea as physician John Weisburger, Ph.D. To him, each cup is more than just a steamy, comforting brew. What has led him to sip almost a dozen cups a day is the growing -- even astonishing --evidence of tea’s health-promoting properties.
According to Weisburger, tea is probably the single best thing you can add to your diet to ward off serious illness. This conviction will doubtless raise a few hackles among colleagues who give that honor to fresh fruit and vegetables. But Weisburger, who chaired two international scientific symposiums on tea and human health, is convinced of his message.
As evidence, he points to numerous studies suggesting that tea -- which made its way slowly to the west after originating in China more than 4,000 years ago --can help prevent cancer and heart disease.
That would seem endorsement enough for tea, which, next to water, is already the most widely consumed beverage in the world. But the latest news about tea may invite even some loyal coffee drinkers to reconsider their choice: Researchers have found that tea -- with or without milk -- may actually help strengthen bones in postmenopausal women.
When tea prevails
Women age 65 to 75 who drank at least one cup of tea every day had significantly higher bone density in the spine and thighs -- common areas of fractures caused by osteoporosis -- than women of the same age who didn’t drink any tea, according to a British study published in the April 2000 issue of the American Journal of Clinical Nutrition.
Comparing 1,134 tea drinkers to 122 non-tea-drinkers, researchers at the University of Cambridge School of Medicine concluded that drinking caffeinated tea may protect against osteoporosis -- even though high caffeine intake has been linked with an increased risk of reduced bone density. As the British researchers point out, most studies are from populations where coffee serves as the major source of caffeine.
While researchers have yet to determine how tea works on bones, they suspect that antioxidants are key players. Tea antioxidants, called polyphenols, may be 100 times as effective as vitamin C and 25 times as effective as vitamin E, according to Weisburger. These antioxidants neutralize free radicals --destructive byproducts of the body’s natural chemical processes. (Unfortunately for herbal tea drinkers, herbal teas are made from altogether different plants and spices and often contain no polyphenols at all.) Polyphenols’ ability to protect the body from free-radical damage may be behind tea’s two best-studied benefits --protection against cancer and lower heart disease risk.
A barrier to cancer?
Whether tea really helps prevent cancer is still under debate, but research in its favor is piling up. In one of the largest studies to date, Iowa researchers found that tea may be a powerful cancer fighter, according to a study published in the July 1996 issue of the American Journal of Epidemiology. The study of more than 35,000 postmenopausal women showed that those who drank at least two cups of black tea a day were 40 percent less likely to develop urinary tract cancer and 68 percent less likely to develop cancer in the digestive tract than women who did not drink tea.
Other research shows that tea may be a promising weapon in the fight against cancers of the stomach, bladder, esophagus and prostate. Moreover, a study in China concluded that smokers who drink tea have a lower incidence of lung cancer, Weisburger noted in an April 1999 summary of the Second International Symposium on Tea and Human Health.
If tea indeed reduces cancer risk, it may be because its polyphenols pack a three-part punch. First, they prevent free radicals from damaging DNA, nipping cancer initiation in the bud. Second, they seem to prevent uncontrolled cell growth, slowing cancer development. And third, certain polyphenols may even destroy cancer cells without harming the surrounding healthy cells. When Japanese researchers combined cancer medications with polyphenols, the treatment was 20 times more effective than the cancer drugs alone, according to a study published in the March 1998 issue of the Japanese Journal of Cancer Research.
Playing on the heart
Other scientists have found that the powerful antioxidants in tea may also help reduce the risk of heart disease. In one study, researchers found that women age 55 or older who drank as little as a cup or two of black tea a day, were 54 percent less likely to have severe atherosclerosis, which can lead to heart attack or stroke, than those who did not. The more tea they drank, the less their risk, according to a study published in the October 11, 1999 issue of the Archives of Internal Medicine.
That could be because the antioxidants work by preventing “bad” (LDL, low-density lipoprotein) cholesterol from promoting the plaque build-up that clogs arteries, researchers speculate. And by preventing atherosclerosis, tea antioxidants can help the arteries supply nourishing blood to the heart and the rest of the body.
A matter of health
All this research has probably got you putting the kettle on the stove. But until further studies are done, most health care professionals say the best way to prevent cancer, heart disease and other diet-related ills is to enjoy a diet that’s low in fat and high in fiber, with lots of antioxidant-rich foods.
But by all means, include some green or black tea. If Weisburger and other researchers are right, you could be one sip closer to a long and healthy life.
Green tea, which has been reported to have anticancer properties and to raise levels of antioxidants in the blood that may ward off heart disease, now appears to have the potential to promote weight loss. A new study in the March issue of the International Journal of Obesity concludes that green tea extract increases the burning of calories and fat needed to lose weight.
Previous animal studies showed that green tea extract increased thermogenesis, which is the generation of body heat that occurs as a result of normal digestion, absorption, and metabolization of food. In previous human studies, the authors showed that consumption of green tea increased thermogenesis as well as energy expenditure and fat loss in healthy men, suggesting that green tea in liquid or capsule form may be an effective way to aid weight loss.
In the new study, conducted by Abdul Dulloo, from the Institute of Physiology at the University of Fribourg in Switzerland, researchers exposed a particular type of fatty tissue from rats to caffeine and to green tea extract containing small concentrations of caffeine.
Green tea containing caffeine significantly increased thermogenesis by 28% to 77%, depending on dose, whereas caffeine alone resulted in no significant increase. When the stimulant ephedrine was added to green tea with caffeine, the increase was even more significant compared with caffeine alone and ephedrine alone. Caffeine and ephedrine are used together in some herbal weight loss preparations, but there are many safety concerns regarding ephedrine because it raises heart rate and blood pressure.
Dulloo and colleagues also tested the plant compound EGCG found in green tea. They found that the stimulant ephedrine alone had no effect on thermogenesis, but that caffeine plus ephedrine resulted in an 84% increase. However, adding EGCG to the caffeine plus ephedrine mix increased thermogenesis even further.
“Our studies ... raise the possibility that the therapeutic potential of the green tea extract, or indeed a combination of EGCG and caffeine, may be extended to the management of obesity,” Dulloo and co-authors write.
A researcher who reviewed the study for WebMD says that while the work is interesting and extends this group’s previous findings by showing that compounds in green tea other than caffeine are involved in thermogenesis, caution should be used in interpreting animal data and applying it to humans.
“They used [a particular type of fatty tissue] from rats and we don’t really know how significant that tissue is in humans or if it is different in obese vs. non-obese people,” says Sheri Zidenberg-Cherr, PhD. “It doesn’t rule out the significance of the findings, and it is a good model to use to look at the effects of caffeine and the combination of caffeine and the [plant] compounds that are present in green tea, but until better clinical trials are done in humans, it’s hard to say what the physiological significance of this actually may be.”
Zidenberg-Cherr, who is an associate professor of nutrition at the University of California, Davis, also points out that thermogenesis plays only a very small role in energy expenditure in adults. Most of the energy expended is used to maintain basic body functions such as breathing and the flow of blood throughout the body.
She says green tea may have many health benefits due to its plant compounds, but cautions that it is not the answer to weight-loss woes. “Green tea can’t be used, and it shouldn’t be used, as a ‘magic bullet’ for weight loss,” she tells WebMD. “You’ve got to combine it with other changes, including increasing physical activity and reducing a high-calorie diet.”
Ladies, start your teapots! A new study from England shows that tea may build and strengthen bones -- protecting women against osteoporosis. If milk is added to the tea, the benefit is boosted even more.
Although several studies have cited caffeine intake a risk factor for osteoporosis and hip fracture in women, at least two European studies have reported that tea drinking protected against hip breaks.
The current study shows that “the magnitude of the effects of drinking tea was notable,” writes lead author Verona M. Hegarty, PhD, a gerontology researcher at England’s University of Cambridge School of Medicine. Older women who drank tea had higher bone mineral density measurements, an indicator of bone health, than those who did not drink tea. “Nutrients found in tea ... [may] protect against osteoporosis in older women,” concludes Hegarty.
Her study, which involved over 1,200 women living in Cambridge, is published in this month’s issue of the American Journal of Clinical Nutrition.
The women completed questionnaires regarding their health and lifestyle that included questions on daily tea and coffee consumption, smoking habits, physical activity, alcohol intake, whether they drank caffeinated or decaffeinated coffee, whether coffee was instant or ground, whether they used hormone replacement therapy, if they added milk to tea, and so on. Each also had their bone mineral density measured, which showed bone strength in the spine and the area where hip breaks most often occur.
Among the women, there were over 1,100 tea drinkers and just about 120 non-tea drinkers, all between the ages of 65 and 76.
Tea drinkers had significantly greater bone mineral density measurements. Among coffee drinkers, those who also drank tea had significantly higher measurements as well.
“These findings were independent of smoking status, use of hormone replacement therapy, coffee drinking, and whether milk was added to tea,” says Hegarty. Also, number of cups of tea per day did not seem to play a role, and women who added milk to their tea had much higher bone mineral density in the hip area.
Though more study is needed, Hegarty suggests that tea has components that weakly mimic the effect of the female hormone, estrogen --documented by other researchers -- and may be important in maintaining bone mineral density in postmenopausal women. Hegarty writes that tea’s attributes may have little effect in younger women and men but may be important in keeping bones healthy in older women.
“This research presents some interesting findings,” Pamela Meyers, PhD, tells WebMD. “Most research on teas, especially on green tea, has looked at its ability to lower risks of cancer and heart disease. This is the first I have seen that has researched the effects of tea on BMD.” Meyers is a clinical nutritionist and assistant professor at Kennesaw State University near Atlanta.
However, says Meyers, she would like to see more complete data on intake of animal protein, calcium, caffeinated sodas and exercise -- all factors that can affect bone density. She reminds women that high consumption of protein and sodas may increase risk of osteoporosis, whereas extra calcium and exercise can improve bone density. “I would like to see more studies into the [estrogen effects] of tea, both green and black,” she says.
Scientific research has shown that caffeine consumption increases the risk of osteoporosis, but a new study shows that tea may actually offer a protective effect against the disease. In a British study, women who consumed tea had significantly greater bone mineral density when compared to non-tea drinkers. Researchers suspect that substances in tea can mimic the effects of estrogen in protecting bones.
Tea drinkers take heart. People who drink tea each day significantly reduce their chances of atherosclerosis, or hardening of the arteries, according to a study published this week in the Archives of Internal Medicine.
Those who drank one or two cups a day lowered their risk by 46 percent. For those who drank four cups a day, the risk dropped by 69 percent.
Women seem to benefit more by drinking tea, the second most consumed beverage in the world after water. And adding milk, honey, lemon or sugar do not diminish the positive health effects, experts said.
“If can be linked directly that consumption of tea prevents development of blockages, then obviously tea would become a very important part of our dietary counseling for patients who have heart trouble or are at risk for heart attack or stroke,” said Dr. David Vorchheimer of the Mt. Sinai School of Medicine.
The beneficial effects of tea are probably due to bio- flavanoids, natural substances that act as powerful anti- oxidants, limiting the effects of free radicals in the body.
“Free radicals are very damaging because they can trigger a chain reaction,” said Dr. Michael Gaziano of Brigham & Women’s Hospital. “One free radical can damage thousands and thousands of lipid molecules. So the reaction, we like to stop it early on in the process.”
Most studies supporting the health benefits of tea have concerned black tea, the most widely consumed tea in the world. Green tea also has anti-oxidant properties, but experts say more research is needed.
“If you have 1 or 2 percent of the population drinking one kind of herbal tea, and 1 or 2 percent of the population drinking another kind of herbal tea, it might be very difficult for us to see any kind of association given those small numbers,” said Gaziano.
Researchers caution that more studies would be necessary to determine if tea is directly responsible for the health benefits.
“The tea itself might have had nothing to do with the prevention of heart attacks. The tea might have been a marker for patients who live a healthy lifestyle, people who avoid caffeine, who don’t smoke, who exercise,” said Vorchheimer.
Although tea has caffeine, most doctors see no reason why people should stop drinking it. Caffeine can increase heart rate and blood pressure, but a cup or two a day of tea, which has half the caffeine of coffee, probably will not hurt.
(You may want to add a cup of tea to your daily menu. A new study shows tea -- either black or green, hot or cold -- may prevent some cancers, especially oral cancers.
A researcher at the Chinese Academy of Preventative Medicine in Beijing studied 59 patients with precancerous lesions in the mouth. When patients drank or applied tea to the mouth, the precancerous cells stopped growing and the lesions began to heal.
These findings were presented Tuesday at the Second International Scientific Symposium on Tea & Human Health, in Washington.
Other new research adds weight to the idea tea may work to slow the growth of lung and colon cancers, although this has been shown with mice and not yet with people.
Earlier research has shown tea may protect against heart disease and stroke.
Antioxidants in tea may be responsible for the protective effects. Antioxidants stop free radicals which are harmful disease-causing compounds that can damage cells in the body.
While some say tea may contain a stronger concentration of antioxidants than fruits or vegetables, experts point out tea is no magic bullet and good health requires a variety of healthy foods.
Green Tea has long been valued in China for its miraculous medicinal properties for the maintenance of good health. It has been said in China “it is better to drink Green Tea than take medicine”.
Green Tea has been receiving much attention lately. As a result, we now have many medical reports and studies by accredited institutions concluding that Green Tea does contain many healthful and healing properties. Drinking Green Tea has been shown to provide the human body with numerous health enhancing components. Green Tea contains a very high value of Catechin polyphenols that have antioxidant properties that are known to fight against cancer. In addition, Green Tea provides Polysaccharides, Flavonoids, Vitamin B complex, Vitamin C (there’s more vitamin “C” in one cup of green tea than in an orange), Vitamin E, R-Amino Butyric Acid and Fluoride in it’s natural state.
Green tea has higher values of medicinal properties than other teas, because of the special way in which it is dried. This traditional drying technique prevents the tea from the negative effects of fermentation. The now widely recognized health benefits of Green Tea have been mentioned in many newspapers and journals including CNN, USA Today, New York Times, Chinese Daily News, Journal of National Cancer Institute, numerous US Universities and Research Centers. Some of the findings that have been established are:
To help keep you up to date on the latest breaking medical news and other information concerning the health benefits of drinking Green Tea, we have prepared a special Green Tea News, Medical Reports and Information page, where you can read some of the exciting reports and studies that are being done, and learn more about the many reasons why we think everyone should be drinking Green Tea. We are sure you will find them beneficial, very informative, and actually rather exciting.
The report of the National Cancer Institute about the Cancer preventing abilities and Cancer fighting components of Green Tea has added new life to the market trend of this precious commodity, Green Tea. We know as Plantation owners and growers of Xianju Rain Forest Green Tea, that people all over the world are discovering the amazing benefits of this fresh and all natural health product, making it the most popular health product of all time. More and more people who have in the past relied on expensive man made anti-oxidant products are finding it very economical to switch to all natural, and flavorful Green Tea. The fact is, today world wide tea consumption is surpassed by only one other beverage, and that beverage is.... you guessed it! Water.
NEW YORK (AP) -- Japanese researchers are throwing cold water on one of the much-touted benefits of green tea.
Their study in Thursday’s New England Journal of Medicine suggests that drinking green tea does not prevent stomach cancer, as many believe.
Green tea, a common beverage in Asia, burst into the U.S. market in the past few years, fueled by reports of its purported health benefits, including cancer prevention and lowering cholesterol.
But the results of studies, many done in laboratories, have been inconsistent. Some have shown green tea to be beneficial against disease, others have not.
In Japan, researchers looked at stomach cancer because of its high incidence rate there -- it is the most common cancer in Japan -- and the country’s high consumption of green tea.
The study compared cups of tea consumed daily and stomach cancer rates and found no connection.
“If green tea is protective, you’d expect to observe lower cancer rates among the subjects who consume higher cups of green tea,” said Dr. Yoshitaka Tsubono of Tohoku University in Sendai, Japan. “We didn’t see any difference between those who consumed five cups or more with people who consume less than one cup.”
Black tea, green tea and oolong tea all come from the same plant. It is the processing that makes them different. In Japan, green tea is steamed before it is dried.
Scientists believe the antioxidant action of polyphenol compounds in green tea are responsible for its purported health benefits.
In the Japanese study, researchers looked at the green tea drinking habits of 26,311 residents of the Miyagi Prefecture in northern Japan. The residents filled out a questionnaire in 1984 about their health habits, including how much tea they drink. The researchers used a cancer registry and found that 419 of the residents were diagnosed with stomach cancer by 1992.
The study found no connection between the amount of tea consumed and the risk of stomach cancer.
There was also no risk associated with black tea and coffee, although the amounts consumed daily by the residents in the study were substantially lower than green tea.
Tsubono, who drinks more coffee than tea, said people should continue to drink green tea, but “for enjoyment, not for trying to prevent cancer.”
Another tea researcher, Chung S. Yang of Rutgers University in New Jersey, said: “This is not the final word -- just like so many of the studies that show a protective effect are not the final word.”
Sales of green tea in the United States have spiked in the past three years from $2 million to $3 million to $100 million, according to the Tea Council of the USA. That is still a small portion of the overall $4.6 billion tea industry in the United States.
CHICAGO - (AP) Can drinking green tea really protect against two big killers, strokes and cancer? A huge study in Japan suggests yes and no: It might lower your stroke risk but won’t save you from cancer.
The study’s authors say their findings might explain why the Japanese are less likely than Americans to die of heart disease and stroke. Even so, the answers aren’t clear. Green tea has been researched a lot, and many of the studies have come up with conflicting results.
Earlier this year, the U.S. Food and Drug Administration said an analysis found no credible scientific evidence to support manufacturers’ claims that green tea can cut cardiovascular disease risks.
The National Cancer Institute says human studies on tea and cancer prevention have had contradictory results. But there’s still hope and the institute is funding rigorous studies testing whether tea extract can help prevent several kinds of cancer.
Tea contains substances called antioxidants that can help keep cells healthy. Green tea has more of them than black tea, and studies in animals have shown that tea antioxidants called catechins seem to shrink cancerous tumors. Some studies in humans have suggested tea can also help keep arteries and cholesterol healthy.
The current study was funded by the Japanese government and is published in Wednesday’s Journal of the American Medical Association. Dr. Shinichi Kuriyama of Tohoku University in Sendai, Japan is the lead author.
It’s different from many previous studies because it involved so many people — 40,530 Japanese adults. Those who drank lots of green tea were less likely than those who drank only a little tea to die from cardiovascular disease and other causes, but not cancer.
Because tea-drinking is popular among Japanese people from all lifestyles and economic groups, the research seems to refute a criticism of previous studies — that people who drink green tea are higher income and more health-conscious and thus apt to be healthier anyway.
However, heavy tea drinkers in the study also tended to eat more fruits and vegetables, and such a diet also might reduce cardiovascular disease and cancer risks, said John Folts, a professor of medicine at the University of Wisconsin.
Study participants were generally less overweight than Americans, and it’s unknown if similar results would be found in a more diverse group of people, said Alice Lichtenstein, a Tufts University nutrition professor and spokeswoman for the American Heart Association.
The results from this study, which observed people and their habits over several years, “point you in a direction” but aren’t conclusive, she said.
The Japanese volunteers filled out questionnaires on tea-drinking and other habits including diet, alcohol and tobacco use, weight, job and education status, and physical activity.
During seven years of follow-up, 1,134 participants died of cancer and 892 died from cardiovascular disease.
Women who drank five or more cups of green tea daily had a 31 percent lower risk of dying from cardiovascular disease than women who drank less than one cup daily; in men, the comparable reduced risk was 22 percent.
Cardiovascular disease includes heart disease and stroke. While heavy tea drinkers had less heart disease than those who drank little tea, the results suggest the difference for heart disease alone might have been due to chance.
Green tea appeared to work best against clot-related strokes. Among the five-cup-a-day group, women had a 62 percent lower risk of dying from these strokes than women who drank little tea, and for men the reduced risk was 42 percent.
The researchers said more men were smokers, and that might have explained the gender differences since smoking affects cardiovascular disease risks.
There were no significant differences in cancer death rates among heavy and light tea drinkers of either sex.
While the study isn’t the last word on whether tea-drinking is good for you, tea is generally harmless and has no calories, so if you like the taste, most researchers would probably say go ahead and drink it.
“The point is, if you’re drinking green tea, that’s fine. It’s premature to recommend that somebody start drinking” it to protect their health, Lichtenstein said.