All true teas—as distinct from herbal and flower infusions, which afficiandos call tisanes, are made from the leaves of a magnolia-related evergreen tree with the botanical name of Camellia sinensis. Although reaching a height of 30 feet in the wild, on tea plantations (called gardens or estates), the plant is kept as a shrub, constantly pruned to a height of about 3 feet to encourage new growth and for convenient picking.
Tea plants grow only in warm climates but can flourish at altitudes ranging from sea level to 7,000 feet. The best teas, however, are produced by plants grown at higher altitudes where the leaves mature more slowly and yield a richer flavor. Depending upon the altitude, a new tea plant may take from 2-1/2 to 5 years to be ready for commercial picking, but once productive, it can provide tea leaves for close to a century.
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.
Tea plants produce abundant foliage, a camellia-like flower, and a berry, but only the smallest and youngest leaves are picked for tea—the two leaves and bud at the top of each young shoot. The growth of new shoots, called a flush, can occur every week at lower altitudes but takes several weeks at higher ones. The new leaves are picked by hand by "tea pluckers," the best of whom can harvest 40 pounds per day, enough to make 10 pounds of tea.
All tea plants belong to the same species Camellia sinensis, but local growing conditions (altitude, climate, soils, etc.) vary, resulting in a multitude of distinctive leaves. The way the leaves are processed, however, is even more important in developing the individual characteristics of the three predominant types of tea: green, black and oolong.
Green tea is the least processed and thus provides the most antioxidant polyphenols, notably a catechin called epigallocatechin-3-gallate (EGCG), which is believed to be responsible for most of the health benefits linked to green tea. Green tea is made by briefly steaming the just harvested leaves, rendering them soft and pliable and preventing them from fermenting or changing color. After steaming, the leaves are rolled, then spread out and "fired" (dried with hot air or pan-fried in a wok) until they are crisp. The resulting greenish-yellow tea has a green, slightly astringent flavor close to the taste of the fresh leaf.
Powdered tea, called fanning, is mostly the tea which left over from processing, and is the cheapest tea. Since powdered tea steeps quickly in teabags, it is a convenient and inexpensive way to ship tea, and it makes it easy to use a portion for a cup. But powdered tea has an increased surface area, and therefore is immediately exposed to the air, which oxidizes it very quickly.
For this reason, the highest-quality green tea is not ground or powdered. The best tea is kept in whole leaves, carefully packaged to be airtight, and used within two years-more preferably, within 12 months of packaging.
There are a great many kinds of green tea, and Chinese green tea is very different from Japanese or other types of green tea. Chinese prefer the natural ta flavor, and rarely add anything besides jasmine. The exception is medicine; physicians in China routinely prescribe herbs or flowers to be added to tea. Drinking tea daily is taken for granted by most people in China, though younger generations drink less.
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.
Green tea just keeps getting better. To add to the abundance of health-improving qualities of the beverage, UAB Researcher Santosh Katiyar, Ph.D., associate professor of dermatology, claims that it can reduce the risk of skin cancer. According to Katiyar, the rich tumor-inhibiting green tea polyphenols, which include the antioxidant, epigallocatechin-3-gallate (EGCG), protect the skin from ultraviolet radiation-induced damage and prevent skin tumor formation. "Green tea prevents UV radiation induced suppression of the immune system, which has been considered a risk factor for the development of skin cancer," he said.
Katiyar's green tea research was most recently published in the May edition of the Journal of Nutritional Biochemistry. He has devoted the past 17 years to finding ways to prevent skin cancer. Grape and black raspberry consumption can also help prevent skin cancer, he said.
Green tea's antioxidants, called catechins, scavenge for free radicals that can damage DNA and contribute to cancer, blood clots, and atherosclerosis. Grapes and berries, red wine, and dark chocolate also have potent antioxidants.
Because of green tea's minimal processing -- its leaves are withered and steamed, not fermented like black and oolong teas -- green tea's unique catechins, especially epigallocatechin-3-gallate (EGCG), are more concentrated.
But there's still a question of how much green tea you need to drink to reap its health benefits. EGCG is not readily "available" to the body; in other words, EGCG is not always fully used by the body.
"We must overcome the issue of poor bioavailability [and other issues] in order to get the most out of their benefits," says Tak-Hang Chan, PhD, professor emeritus in the department of chemistry at McGill University in Montreal. Chan has studied the use of a synthetic form of EGCG in shrinking prostate cancer tumors in mice, with success.
Marji McCullough, ScD, RD, the American Cancer Society's strategic director of nutritional epidemiology, says human studies haven't yet proven what researchers like Chan have discovered in the lab: green tea's EGCG regulates and inhibits cancer growth and kills cells that are growing inappropriately.
"Epidemiologically, one of the challenges is finding populations that drink enough green tea and have for a long time," she says. "With cancer, it's always difficult to find the exposure time," or the point at which cancer cells begin to develop.
Still, it's difficult not to be intrigued by a few human studies that have shown that drinking at least two cups of green tea daily inhibits cancer growth.
One of them, a study conducted in Japan that involved nearly 500 Japanese women with Stage I and Stage II breast cancer, found that increased green tea consumption before and after surgery was associated with lower recurrence of the cancers.
Studies in China have shown that the more green tea that participants drank, the less the risk of developing stomach cancer, esophageal cancer, prostate cancer, pancreatic cancer, and colorectal cancer.
Finally, a recent analysis of 22 studies that probed the correlation between high tea consumption and reduced risk for lung cancer concluded that by increasing your daily intake of green (not black) tea by two cups may reduce the risk of developing lung cancer by 18%.
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.
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.
It seems to be, but there are conflicting results of a few epidemiological studies conducted in the East and West.
In a study that involved 500 Japanese men and women, researchers found that drinking at least four cups of green tea every day may be related to the reduced severity of coronary heart disease among the male participants.
A Dutch study of more than 3,000 men and women found that the more tea consumed, the less severe the clogging of the heart's blood vessels, especially in women.
As Goldberg suggests, lifestyle and overall diet are critical to the outcomes of these studies.
But green tea's antioxidants are dilators, she says, because they improve the flexibility of blood vessels and make them less vulnerable to clogging -- and antioxidant-rich blueberries and pomegranates do the same.
"I think people should know these are important studies, that everyday foods that are an option may actually have health benefits," Goldberg says. "I think green tea, because of its antioxidant value, may have heart benefits, but it's not something we regularly prescribe to people, because there isn't as much evidence as there is in exercise's ability to improve heart health."
Green tea and its extract have been shown to fight obesity and lower LDL "bad" cholesterol -- two risk factors for heart disease and diabetes -- but in very limited studies. One study in the Netherlands and a study in Japan showed that green tea did both.
In the Dutch study, participants who drank caffeinated green tea lost more weight, but even those who typically drank the decaf variety saw a decrease in their waistlines and body weight. Researchers speculated that the caffeine helps with fat oxidation.
In the Japanese study, 240 men and women were given varying amounts of green tea extract for three months. Those who got the highest amount lost fat and weight and had lower blood pressure and lower LDL "bad" cholesterol.
The secret of green tea lies in the fact it is rich in catechin polyphenols, particularly epigallocatechin gallate (EGCG). EGCG is a powerful anti-oxidant: besides inhibiting the growth of cancer cells, it kills cancer cells without harming healthy tissue. It has also been effective in lowering LDL cholesterol levels, and inhibiting the abnormal formation of blood clots. The latter takes on added importance when you consider that thrombosis (the formation of abnormal blood clots) is the leading cause of heart attacks and stroke.
For years, researchers were puzzled by the fact that, despite consuming a diet rich in fat, the French have a lower incidence of heart disease than Americans. The answer was found to lie in red wine, which contains resveratrol, a polyphenol. In a 1997 study, researchers from the University of Kansas determined that EGCG is twice as powerful as resveratrol, which may explain why the rate of heart disease among Japanese men is quite low, even though approximately seventy-five percent are smokers.
Why don't other Chinese teas have similar health-giving properties? Green, oolong, and black teas all come from the leaves of the Camellia sinensis plant. What sets green tea apart is the way it is processed. Green tea leaves are steamed, which prevents the EGCG compound from being oxidized. By contrast, black and oolong tea leaves are made from fermented leaves, which results in the EGCG being converted into other compounds that are not nearly as effective in preventing and fighting various diseases.
New evidence is emerging that green tea can even help dieters. In November, 1999, the American Journal of Clinical Nutrition published the results of a study at the University of Geneva in Switzerland. Researchers found that men who were given a combination of caffeine and green tea extract burned more calories than those given only caffeine or a placebo.
Green tea can even help prevent tooth decay! Just as its bacteria-destroying abilities can help prevent food poisoning, it can also kill the bacteria that causes dental plaque. Meanwhile, skin preparations containing green tea - from deodorants to creams - are starting to appear on the market.
Green tea is safe for most adults when used in moderate amounts.
There have been some case reports of liver problems in people taking concentrated green tea extracts. This problem does not seem to be connected with green tea infusions or beverages. Although these cases are very rare and the evidence is not definitive, experts suggest that concentrated green tea extracts be taken with food, and that people should discontinue use and consult a heath care practitioner if they have a liver disorder or develop symptoms of liver trouble, such as abdominal pain, dark urine, or jaundice.
Green tea and green tea extracts contain caffeine. Caffeine can cause insomnia, anxiety, irritability, upset stomach, nausea, diarrhea, or frequent urination in some people.
Green tea contains small amounts of vitamin K, which can make anticoagulant drugs, such as warfarin, less effective.
Tell all your health care providers about any complementary and alternative practices you use. Give them a full picture of what you do to manage your health. This will help ensure coordinated and safe care.
Green tea is LIKELY SAFE for most adults. Green tea extract is POSSIBLY SAFE for most people for short-term use. In some people, green tea can cause stomach upset and constipation. Green tea extracts have been reported to cause liver problems in rare cases.
Too much green tea — more than five cups per day, for example — is POSSIBLY UNSAFE. It can cause side effects because of the caffeine. These side effects can range from mild to serious and include headache, nervousness, sleep problems, vomiting, diarrhea, irritability, irregular heartbeat, tremor, heartburn, dizziness, ringing in the ears, convulsions, and confusion. Green tea seems to reduce the absorption of iron from food. Drinking very high doses of green tea can actually be fatal. The fatal dose of caffeine in green tea is estimated to be 10-14 grams (150-200 mg per kilogram). Serious toxicity can occur at lower doses.
Caffeine is POSSIBLY SAFE in children in amounts commonly found in foods.
Green tea interacts with many medications, as explained below.
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, to be on the safe side, talk to your health care provider before use.
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.
Pregnancy and breast-feeding: If you are pregnant or breast-feeding, green tea in small amounts is POSSIBLY SAFE. Do not drink more than 2 cups a day of green tea. This amount of tea provides about 200 mg of caffeine. Consuming more than this amount has been linked to an increased risk of miscarriage and other negative effects. Caffeine passes into breast milk and can affect a nursing infant. Don’t drink an excessive amount of green tea if you are breast-feeding.
“Tired blood” (anemia): Drinking green tea may make anemia worse.
Anxiety disorders: The caffeine in green tea might make anxiety worse.
Bleeding disorders: Caffeine might increase the risk of bleeding. Don’t drink green tea if you have a bleeding disorder.
Heart conditions: Caffeine in green tea might cause irregular heartbeat.
Diabetes: Caffeine might affect blood sugar control. If you drink green tea and have diabetes, monitor your blood sugar carefully.
Diarrhea: Green tea contains caffeine. The caffeine in green tea, especially when taken in large amounts, can worsen diarrhea.
Irritable bowel syndrome (IBS): Green tea contains caffeine. The caffeine in green tea, especially when taken in large amounts, can worsen diarrhea and might worsen symptoms of IBS.
Glaucoma: Drinking green tea increases pressure inside the eye. The increase occurs within 30 minutes and lasts for at least 90 minutes.
High blood pressure: The caffeine in green tea might increase blood pressure in people with high blood pressure. However, this does not seem to occur in people who regularly drink green tea or other products that contain caffeine.
Liver disease: Green tea extract supplements have been linked to several cases of liver damage. Green tea extracts might make liver disease worse.
Weak bones (osteoporosis): Drinking green tea can increase the amount of calcium that is flushed out in the urine. Caffeine should be limited to less than 300 mg per day (approximately 2-3 cups of green tea). It is possible to make up for some calcium loss caused by caffeine by taking calcium supplements.
Amphetamines interacts with GREEN TEA
Stimulant drugs such as amphetamines speed up the nervous system. By speeding up the nervous system, stimulant medications can make you feel jittery and increase your heart rate. The caffeine in green tea might also speed up the nervous system. Taking green tea along with stimulant drugs might cause serious problems including increased heart rate and high blood pressure. Avoid taking stimulant drugs along with caffeine.
Cocaine interacts with GREEN TEA
Stimulant drugs such as cocaine speed up the nervous system. By speeding up the nervous system, stimulant medications can make you feel jittery and increase your heart rate. The caffeine in green tea might also speed up the nervous system. Taking green tea along with stimulant drugs might cause serious problems including increased heart rate and high blood pressure. Avoid taking stimulant drugs along with caffeine.
Ephedrine interacts with GREEN TEA
Stimulant drugs speed up the nervous system. Caffeine (contained in green tea) and ephedrine are both stimulant drugs. Taking green tea along with ephedrine might cause too much stimulation and sometimes serious side effects and heart problems. Do not take caffeine-containing products and ephedrine at the same time.
Adenosine (Adenocard) interacts with GREEN TEA
Green tea contains caffeine. The caffeine in green tea might block the affects of adenosine (Adenocard). Adenosine (Adenocard) is often used by doctors to do a test on the heart. This test is called a cardiac stress test. Stop consuming green tea or other caffeine-containing products at least 24 hours before a cardiac stress test.
Antibiotics (Quinolone antibiotics) interacts with GREEN TEA
The body breaks down caffeine to get rid of it. Some antibiotics might decrease how quickly the body breaks down caffeine. Taking these antibiotics along with green tea can increase the risk of side effects including jitteriness, headache, increased heart rate, and other side effects.
Some antibiotics that decrease how quickly the body breaks down caffeine include ciprofloxacin (Cipro), enoxacin (Penetrex), norfloxacin (Chibroxin, Noroxin), sparfloxacin (Zagam), trovafloxacin (Trovan), and grepafloxacin (Raxar).
Cimetidine (Tagamet) interacts with GREEN TEA
Green tea contains caffeine. The body breaks down caffeine to get rid of it. Cimetidine (Tagamet) can decrease how quickly your body breaks down caffeine. Taking cimetidine (Tagamet) along with green tea might increase the chance of caffeine side effects including jitteriness, headache, fast heartbeat, and others.
Clozapine (Clozaril) interacts with GREEN TEA
The body breaks down clozapine (Clozaril) to get rid of it. The caffeine in green tea seems to decrease how quickly the body breaks down clozapine (Clozaril). Taking green tea along with clozapine (Clozaril) can increase the effects and side effects of clozapine (Clozaril).
Dipyridamole (Persantine) interacts with GREEN TEA
Green tea contains caffeine. The caffeine in green tea might block the affects of dipyridamole (Persantine). Dipyridamole (Persantine) is often used by doctors to do a test on the heart. This test is called a cardiac stress test. Stop drinking green tea or other caffeine-containing products at least 24 hours before a cardiac stress test.
Disulfiram (Antabuse) interacts with GREEN TEA
The body breaks down caffeine to get rid of it. Disulfiram (Antabuse) can decrease how quickly the body gets rid of caffeine. Taking green tea (which contains caffeine) along with disulfiram (Antabuse) might increase the effects and side effects of caffeine including jitteriness, hyperactivity, irritability, and others.
Estrogens interacts with GREEN TEA
The body breaks down the caffeine in green tea to get rid of it. Estrogens can decrease how quickly the body breaks down caffeine. Taking estrogen pills and drinking green tea can cause jitteriness, headache, fast heartbeat, and other side effects. If you take estrogen pills limit your caffeine intake.
Some estrogen pills include conjugated equine estrogens (Premarin), ethinyl estradiol, estradiol, and others.
Fluvoxamine (Luvox) interacts with GREEN TEA
The body breaks down the caffeine in green tea to get rid of it. Fluvoxamine (Luvox) can decrease how quickly the body breaks down caffeine. Taking green tea along with fluvoxamine (Luvox) might cause too much caffeine in the body, and increase the effects and side effects of caffeine.
Lithium interacts with GREEN TEA
Your body naturally gets rid of lithium. The caffeine in green tea can increase how quickly your body gets rid of lithium. If you take products that contain caffeine and you take lithium, stop taking caffeine products slowly. Stopping caffeine too quickly can increase the side effects of lithium.
Medications for depression (MAOIs) interacts with GREEN TEA
The caffeine in green tea can stimulate the body. Some medications used for depression can also stimulate the body. Drinking green tea and taking some medications for depression might cause too much stimulation of the body and serious side effects including fast heartbeat, high blood pressure, nervousness, and others.
Some of these medications used for depression include phenelzine (Nardil), tranylcypromine (Parnate), and others.
Medications that can harm the liver (Hepatotoxic drugs) interacts with GREEN TEA
Green tea extracts might harm the liver. Taking green tea extracts along with medication that might also harm the liver can increase the risk of liver damage. Do not take green tea extracts if you are taking a medication that can harm the liver.
Some medications that can harm the liver include acetaminophen (Tylenol and others), amiodarone (Cordarone), carbamazepine (Tegretol), isoniazid (INH), methotrexate (Rheumatrex), methyldopa (Aldomet), fluconazole (Diflucan), itraconazole (Sporanox), erythromycin (Erythrocin, Ilosone, others), phenytoin (Dilantin) , lovastatin (Mevacor), pravastatin (Pravachol), simvastatin (Zocor), and many others.
Medications that slow blood clotting (Anticoagulant / Antiplatelet drugs) interacts with GREEN TEA
Green tea might slow blood clotting. Taking green tea along with medications that also slow clotting might increase the chances of bruising and bleeding.
Some medications that slow blood clotting include aspirin, clopidogrel (Plavix), diclofenac (Voltaren, Cataflam, others), ibuprofen (Advil, Motrin, others), naproxen (Anaprox, Naprosyn, others), dalteparin (Fragmin), enoxaparin (Lovenox), heparin, warfarin (Coumadin), and others.
Nicotine interacts with GREEN TEA
Stimulant drugs such as nicotine speed up the nervous system. By speeding up the nervous system, stimulant medications can make you feel jittery and increase your heart rate. The caffeine in green tea might also speed up the nervous system. Taking green tea along with stimulant drugs might cause serious problems including increased heart rate and high blood pressure. Avoid taking stimulant drugs along with caffeine.
Pentobarbital (Nembutal) interacts with GREEN TEA
The stimulant effects of the caffeine in green tea can block the sleep-producing effects of pentobarbital.
Phenylpropanolamine interacts with GREEN TEA
Green tea contains caffeine. Caffeine can stimulate the body. Phenylpropanolamine can also stimulate the body. Taking green tea and phenylpropanolamine together might cause too much stimulation and increase heartbeat, blood pressure and cause nervousness.
Riluzole (Rilutek) interacts with GREEN TEA
The body breaks down riluzole (Rilutek) to get rid of it. Drinking green tea can decrease how quickly the body breaks down riluzole (Rilutek) and increase the effects and side effects of riluzole.
Theophylline interacts with GREEN TEA
Green tea contains caffeine. Caffeine works similarly to theophylline. Caffeine can also decrease how quickly the body gets rid of theophylline. Taking green tea along with theophylline might increase the effects and side effects of theophylline.
Verapamil (Calan, Covera, Isoptin, Verelan) interacts with GREEN TEA
The body breaks down the caffeine in green tea to get rid of it. Verapamil (Calan, Covera, Isoptin, Verelan) can decrease how quickly the body gets rid of caffeine. Drinking green tea and taking verapamil (Calan, Covera, Isoptin, Verelan) can increase the risk of side effects for caffeine including jitteriness, headache, and an increased heartbeat.
Warfarin (Coumadin) interacts with GREEN TEA
Warfarin (Coumadin) is used to slow blood clotting. Large amounts of green tea have been reported to decrease the effectiveness of warfarin (Coumadin). Decreasing the effectiveness of warfarin (Coumadin) might increase the risk of clotting. It is unclear why this interaction might occur. Be sure to have your blood checked regularly. The dose of your warfarin (Coumadin) might need to be changed.
Alcohol interacts with GREEN TEA
The body breaks down the caffeine in green tea to get rid of it. Alcohol can decrease how quickly the body breaks down caffeine. Taking green tea along with alcohol might cause too much caffeine in the bloodstream and caffeine side effects including jitteriness, headache, and fast heartbeat.
Fluconazole (Diflucan) interacts with GREEN TEA
Green tea contains caffeine. The body breaks down caffeine to get rid of it. Fluconazole (Diflucan) might decrease how quickly the body gets rid of caffeine and cause caffeine to stay in the body too long. Taking fluconazole (Diflucan) along with green tea might increase the risk of side effects such as nervousness, anxiety, and insomnia.
Medications for diabetes (Antidiabetes drugs) interacts with GREEN TEA
Green tea contains caffeine. Caffeine might increase blood sugar. Diabetes medications are used to lower blood sugar. Taking some medications for diabetes along with caffeine might decrease the effectiveness of diabetes medications. Monitor your blood sugar closely. The dose of your diabetes medication might need to be changed.
Some medications used for diabetes include glimepiride (Amaryl), glyburide (DiaBeta, Glynase PresTab, Micronase), insulin, pioglitazone (Actos), rosiglitazone (Avandia), chlorpropamide (Diabinese), glipizide (Glucotrol), tolbutamide (Orinase), and others.
Mexiletine (Mexitil) interacts with GREEN TEA
Green tea contains caffeine. The body breaks down caffeine to get rid of it. Mexiletine (Mexitil) can decrease how quickly the body breaks down caffeine. Taking Mexiletine (Mexitil) along with green tea might increase the caffeine effects and side effects of green tea.
Terbinafine (Lamisil) interacts with GREEN TEA
The body breaks down the caffeine in green tea to get rid of it. Terbinafine (Lamisil) can decrease how fast the body gets rid of caffeine. Taking green tea along with terbinafine (Lamisil) can increase the risk of caffeine side effects including jitteriness, headache, increased heartbeat, and other effects.
The following doses have been studied in scientific research:
Doses of green tea vary significantly, but usually range between 1-10 cups daily. The commonly used dose of green tea is based on the amount typically consumed in Asian countries, which is about 3 cups per day, providing 240-320 mg of the active ingredients, polyphenols. To make tea, people typically use 1 teaspoon of tea leaves in 8 ounces boiling water.
For headache or restoring mental alertness: tea providing is up to 250 mg of caffeine per day, or approximately 3 cups of tea per day.
For improving thinking: tea providing 60 mg of caffeine, or approximately one cup.
For reducing cholesterol: drinking 10 or more cups per day has been associated with decreased cholesterol levels. Theaflavin-enriched green tea extract, 375 mg daily for 12 weeks, has also been used for lowering cholesterol.
For human papilloma virus (HPV) infections of the cervix: green tea extract, 200 mg daily alone or in combination with topical green tea ointment, for 8-12 weeks.
For preventing Parkinson’s disease:
Men consuming 421-2716 mg total caffeine (approximately 5-33 cups of green tea) daily have the lowest risk of developing Parkinson’s disease. However, a significantly lower risk is also associated with consumption of as little as 124-208 mg of caffeine (approximately 1-3 cups of green tea) daily.
In women: more moderate caffeine consumption seems to be best, equivalent to approximately 1-4 cups of green tea per day.
For human papillomavirus (HPV) infections of the cervix: green tea ointment alone or in combination with oral green tea extract, twice weekly for 8-12 weeks.
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 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.
One bag of green tea contains 0 calories, approximately 0.06 mg of caffeine, and 80-100 mg of polyphenols, 25-30 mg of which are epigallocatechin-3-gallate (EGCG).
These reviews are from WebMD's homepage.
Reviewer: dukesmom, 55-64 Female on Treatment for less than 1 month (Consumer)
Comment:
I wanted to cut out soda from my daily drinks. I drank about 40 ozs per day. After 3 days, I experienced pain in my sides(I attributed it to kidney pain). I stopped using it for now. I am not on any meds except occational acetametaphine. This was green tea with ginseng and honey.
Reviewer: Sally Griffin, 65-74 Female on Treatment for 6 months to less than 1 year (Consumer)
Comment:
This treatment has worked very well for me. A unexpected side effect benefit has been the disappearance of a skin disorder which my dermaologist had been treating with a steroid cream which only calmed the rash but did cure it. The rash has completly gone away. To prove the theory that the green tea was the agent which helped cure the rash, I discontinued use of the green tea for several weeks and the rash returned in the exact same way and location on my hand. I started taking the green tea capsules again and again the rash disappeared. I am delighted at the results and will share this exciting news with my dermatologists on my next visit.
Reviewer: tdtucker7369, 35-44 Female on Treatment for 1 to 6 months (Consumer)
Comment:
I now have abnormal liver counts since I have been taking Green Tea Extract in attempt to lose weight. I wish I would have read the side effects on WebMd prior to taking I probably would have decided not to take it.
Reviewer: Guille, 25-34 Female on Treatment for 1 to 6 months (Consumer)
Comment:
I started drinking decaffeinated green tea for about 2-3 months before I got pregnant and during the 1st month of pregnancy. I later found out that green tea takes folic acid from your body. My baby was born with a neural tube defect. Of course I'll never know if it was due to the green tea taking the folic acid from my system or not. But just in case, please dont drink green tea in the months leading up to conception or during pregnancy.
Reviewer: JennaA54, 45-54 Female on Treatment for 1 to 6 months (Consumer)
Comment:
I came down with mononucleosis in my fifties, unlike most people. I felt terrible and couldn't do anything but rest, so said my doctor. I was told Green Tea would help, and was referenced to ... an antiviral health supplement that has Green Tea as one of its five main ingredients. After a few weeks of taking ... I felt much better. I had a lot more energy and slept much more restfully. I’m now able to enjoy wonderful times with my granddaughter and the rest of my family without feeling perpetually exhausted.
Reviewer: pennywhistle, Female on Treatment for 1 to less than 2 years (Consumer)
Comment:
I drink 6 cups at least a day i started when i found out i had type 2 diabetes.
Reviewer: 25-34 Female on Treatment for 5 to less than 10 years (Consumer)
Comment:
I enjoy the taste, as plain as it is, and green tea ... has helped me feel better in general. Upon reading the uses and information this website provides, I have certainly noticed a difference in my overall health. I am not taking it for anything specific. In general, I've felt better, maintained weight, and find green tea a healthy, good choice of drink.
Reviewer: EDDIE, 45-54 Male on Treatment for less than 1 month (Consumer)
Comment:
Im Losing weight and stopped smoking because of my health, Iam using nicotine gum to help me. However I started to have mouth and tongue sores from chewing. Using green tea has helped me loose weight and has healed the sores I had.
Reviewer: 45-54 Female on Treatment for 2 to less than 5 years
Comment:
A large mug of green iced tea 4 to 5 days per week eliminates hot flashes for me.
Reviewer: kygal, 35-44 Female (Consumer)
Comment:
I started drinking green tea over 2 year ago - and have not been sick one day since. I have children who have gone throug illness (sneezing and coughing on me) and yet - I still say healthy. I drink one to two cups in the morning - using the same tea bag for both cups. I've had NO side affects to this tea.
Reviewer:
Comment:
i have no experiences with it im trying to find out if it will work for me i have a rash i guess aroung nose and mouth im trying to find something that might work
Reviewer: Male
Comment:
I drink 6 cups of home brewed green tea and it has lowed my blood sugar levels by 50 points
Reviewer: mustangchic, 19-24 Female on Treatment for 2 to less than 5 years (Consumer)
Comment:
Since i've been taking green tea tablits I have noticed some weight loss along with an increase in daily energy. Also my nails and hair grrow faster and stronger.