Green Tea

Botanicals

18/Description

About

Green tea is made from the Camellia sinensis plant. The dried leaves and leaf buds of Camellia sinensis are used to produce various types of teas. Green tea is prepared by steaming and pan-frying these leaves and then drying them. Other teas such as black tea and oolong tea involve processes in which the leaves are fermented (black tea) or partially fermented (oolong tea).

Green tea is taken by mouth to improve mental alertness and thinking.

It is also taken by mouth for depression, non-alcoholic fatty liver disease (NAFLD), inflammatory bowel disease (ulcerative colitis or Crohn's disease), weight loss and to treat stomach disorders, vomiting, diarrhea, headaches, and bone loss (osteoporosis).

Some people take green tea by mouth to prevent various cancers, including breast cancer, prostate cancer, colon cancer, gastric cancer, lung cancer, liver cancer, solid tumor cancers, leukemia, and skin cancer related to exposure to sunlight. Some women use green tea to fight human papilloma virus (HPV), which can cause genital warts, the growth of abnormal cells in the cervix (cervical dysplasia), and cervical cancer.

Green tea is also taken by mouth for Parkinson's disease, diseases of the heart and blood vessels, diabetes, low blood pressure, chronic fatigue syndrome (CFS), dental cavities (caries), kidney stones, and skin damage.

Instead of drinking green tea, some people apply green tea bags to their skin to soothe sunburn and prevent skin cancer due to sun exposure. Green tea bags are also used to decrease puffiness under the eyes, as a compress for tired eyes or headache, and to stop gums from bleeding after a tooth is pulled. A green tea footbath is used for athlete's foot.

Some people gargle with green tea to prevent colds and flu. Green tea extract is also used in mouthwash to reduce pain after tooth removal. Green tea in candy is used for gum disease.

Green tea is used in an ointment for genital warts.

In food, people drink green tea as a beverage

How it works

The useful parts of green tea are the leaf bud, leaf, and stem. Green tea is not fermented and is produced by steaming fresh leaves at high temperatures. During this process, it is able to maintain important molecules called polyphenols, which seem to be responsible for many of the benefits of green tea.

Polyphenols might be able to prevent inflammation and swelling, protect cartilage between the bones, and lessen joint degeneration. They also seem to be able to fight human papilloma virus (HPV) infections and reduce the growth of abnormal cells in the cervix (cervical dysplasia). Research cannot yet explain how this works.

Green tea contains 2% to 4% caffeine, which affects thinking and alertness, increases urine output, and may improve the function of brain messengers important in Parkinson's disease. Caffeine is thought to stimulate the nervous system, heart, and muscles by increasing the release of certain chemicals in the brain called "neurotransmitters."

Antioxidants and other substances in green tea might help protect the heart and blood vessels.

Effectiveness

Likely Effective
Genital warts

A specific green tea extract ointment (Veregen, Bradley Pharmaceuticals; Polyphenon E ointment 15%, MediGene AG) is FDA-approved for treating genital warts. Applying the ointment for 10-16 weeks seems to clear these types of warts in 24% to 60% of patients.

High cholesterol

People to consume higher amounts of green tea seem to have lower levels of cholesterol, low-density lipoprotein (LDL or "bad") cholesterol, and triglycerides, as well as higher levels of high-density lipoprotein (HDL or "good") cholesterol. Consuming green tea or taking green tea extract containing 150 to 2500 mg of green tea catechins, an antioxidant found in green tea, daily for up to 24 weeks reduces total cholesterol and low-density lipoprotein (LDL or "bad") cholesterol in people with high levels of blood fats or cholesterol.

Concerns

Likely safe

Green tea is LIKELY SAFE for most adults when consumed as a drink in moderate amounts or when green tea extract is applied to the skin as a specific ointment (Veregen, Bradley Pharmaceuticals), short-term

Possibly safe

Green tea extract is POSSIBLY SAFE for most people when taken by mouth for up to 2 years, when applied to the skin as other ointments short-term, or when used as a mouthwash short-term. In some people, green tea can cause stomach upset and constipation. Green tea extracts have been reported to cause liver and kidney problems in rare cases

Possibly unsafe

Green tea is POSSIBLY UNSAFE when taken by mouth long-term or in high-doses. 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

Likely unsafe

Drinking very high doses of green tea is LIKELY UNSAFE and 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.

18/Warnings

Warnings

Children: Green tea isPOSSIBLY SAFEfor children when used in amounts commonly found in foods and beverages or when used for gargling three times daily for up to 90 days.

Pregnancy and breast-feeding: If you are pregnant or breast-feeding, green tea in small amounts - about 2 cups per day - is POSSIBLY SAFE. This amount of green tea provides about 200 mg of caffeine. However, drinking more than 2 cups of green tea per day is POSSIBLY UNSAFE. Consuming more than 2 cups of green tea daily has been linked to an increased risk of miscarriage and other negative effects due to the caffeine content. Also, green tea might increase the risk of birth defects associated with folic acid deficiency. In women who are nursing, caffeine passes into breast milk and can affect a nursing infant. Don't drink an excessive amount of green tea if you are pregnant or 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 in green tea 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 in green tea 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.

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.

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.

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.

Interactions

Always consult with your doctor.
Major
Amphetamines

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

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

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.

Nadolol (Corgard)

Green tea might decrease how much nadolol (Corgard) the body absorbs. Taking green tea along with nadolol (Corgard) might decrease the effectiveness of nadolol (Corgard).

Moderate
Adenosine (Adenocard)

Green tea contains caffeine. The caffeine in green tea might block the effects of adenosine (Adenocard). Adenosine (Adenocard) is often used by doctors to do a test on the heart, called a cardiac stress test. Stop consuming green tea or other caffeine-containing products at least 24 hours before a cardiac stress test.

Bortezomib (Velcade)

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).The body breaks down the caffeine in green tea to get rid of it. Birth control pills can decrease how quickly the body breaks down caffeine. Taking green tea along with birth control pills can cause jitteriness, headache, fast heartbeat, and other side effects.Some birth control pills include ethinyl estradiol and levonorgestrel (Triphasil), ethinyl estradiol and norethindrone (Ortho-Novum 1/35, Ortho-Novum 7/7/7), and others.Bortezomib (Velcade) is used in certain types of cancers. Green tea might interact with bortezomib (Velcade) and decrease its effectiveness for treating certain types of cancer. If you take bortezomib (Velcade) avoid taking green tea products.

Cimetidine (Tagamet)

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)

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)

Green tea contains caffeine. The caffeine in green tea might block the affectseffects of dipyridamole (Persantine). Dipyridamole (Persantine) is often used by doctors to do a test on the heart 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)

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.

Fluvoxamine (Luvox)

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.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

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 used to treat cancer (Boronic acid-based proteasome inhibitors)

Green tea contains caffeine. Caffeine can stimulate the heart. Some medications for asthma can also stimulate the heart. Taking caffeine with some medications for asthma might cause too much stimulation and cause heart problems.Some medications for asthma include albuterol (Proventil, Ventolin, Volmax), metaproterenol (Alupent), terbutaline (Bricanyl, Brethine), and isoproterenol (Isuprel).Caffeine in green tea can stimulate the body. Some medications used for depression can also stimulate the body. Taking green tea that contains caffeine along with some medications for depression might cause 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.Some medications are moved by pumps in cells. Green tea might change how these pumps work and decrease how much of some medications get absorbed by the body. This could make these medications less effective.Some of these medications that are moved by pumps in cells include bosentan (Tracleer), celiprolol (Celicard, others), etoposide (VePesid), fexofenadine (Allegra), fluoroquinolone antibiotics, glyburide (Micronase, Diabeta), irinotecan (Camptosar), methotrexate, nadolol (Corgard), paclitaxel (Taxol), saquinavir (Fortovase, Invirase), rifampin, statins, talinolol, torsemide (Demadex), troglitazone, and valsartan (Diovan).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.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 ardeparin (Normiflo), aspirin, clopidogrel (Plavix), diclofenac (Voltaren, Cataflam, others), dipyridamole (Persantine), ibuprofen (Advil, Motrin, others), naproxen (Anaprox, Naprosyn, others), dalteparin (Fragmin), enoxaparin (Lovenox), heparin, ticlopidine (Ticlid), warfarin (Coumadin), and others.Green tea might interact with some medications used to treat cancer (boronic acid-based proteasome inhibitors). This might decrease its effectiveness of these medications for treating certain types of cancer. If you take one of these medications for cancer, avoid taking green tea products. Some of these drugs include bortezomib (Velcade).

Nicotine

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)

The stimulant effects of the caffeine in green tea can block the sleep-producing effects of pentobarbital (Nembutal).

Phenylpropanolamine

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, increase blood pressure, and cause nervousness.

Riluzole (Rilutek)

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

Stimulant drugs speed up the nervous system and can make you feel jittery and speed up your heartbeat. Green tea contains caffeine, which can 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.Some stimulant drugs include diethylpropion (Tenuate), epinephrine, phentermine (Ionamin), pseudoephedrine (Sudafed), and many others.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)

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)

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.

Minor
Alcohol

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)

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.

Mexiletine (Mexitil)

Some medications are changed and broken down by the liver. Green tea might decrease how quickly the liver breaks down some medications. Taking green tea while taking some medications that are broken down by the liver can increase the effects and side effects of some medications. However, it is not known if this is a big concern. Talk to your healthcare provider if you are taking any medications that are changed by the liver.Some medications changed by the liver include lovastatin (Mevacor), ketoconazole (Nizoral), itraconazole (Sporanox), fexofenadine (Allegra), triazolam (Halcion), and many others.Green tea contains caffeine. There is conflicting evidence that caffeine might either increase or decrease 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.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.

Midazolam (Versed)

The body breaks down midazolam (Versed) to get rid of it. Green tea might decrease how quickly the body breaks down midazolam (Versed). Taking green tea along with midazolam (Versed) might increase the effects and side effects of midazolam (Versed). However, it is not known if this is a big concern. Talk with you healthcare provider if you are taking midazolam.

Nicardipine (Cardene)

A chemical in green tea called EGCG might increase how much nicardipine is absorbed in the body. In theory, green tea might increase the effects and side effects of nicardipine. But it's not clear if this is a real concern.

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