Supplements Details

Green Tea

What other names is Green Tea known by?

Camellia sinensis, Camellia thea, Camellia theifera, Constituant Polyphénolique de Thé Vert, CPTV, EGCG, Epigallo Catechin Gallate, Épigallo-Catéchine Gallate, Epigallocatechin Gallate, Extrait de Camellia Sinensis, Extrait de Thé, Extrait de Thé Vert, Extrait de Thea Sinensis, Green Sencha Tea, Green Tea Extract, Green Tea Polyphenolic Fraction, GTP, GTPF, Japanese Tea, Kunecatechins, Poly E, Polyphenon E, PTV, Té Verde, Tea, Tea Extract, Tea Green, Thé, Thé de Camillia, Thé Japonais, Thé Vert, Thé Vert de Yame, Thé Vert Sensha, Thea bohea, Thea sinensis, Thea viridis, Yame Green Tea, Yame Tea.

What is Green Tea?

Green tea is a product made from the Camellia sinensis plant. The fresh leaves are used to make medicine.

Is Green Tea effective?

There is some scientific evidence that drinking green tea can improve thinking skills, and might help lower cholesterol and other fats called triglycerides. Green tea consumption might also prevent or delay Parkinson's disease and possibly help to prevent cancer of the bladder, esophagus, and pancreas. But green tea does not seem to help prevent stomach cancer.

There isn't enough information to know if green tea is effective for the other conditions people use it for including: kidney disease, heart disease, kidney stones, tooth decay, and others.

Likely Effective for...

  • Genital warts. A specific green tea extract ointment (Veregen, Bradley Pharmaceuticals) is FDA-approved for treating genital warts.
  • Increasing mental alertness, due to the caffeine content of green tea.

Possibly Effective for...

  • Preventing dizziness upon standing up (orthostatic hypotension) in older people.
  • Preventing bladder, esophageal, ovarian, and pancreatic cancers.
  • Reducing the risk of Parkinson's disease.
  • Decreasing high levels of fat in the blood (hyperlipidemia).
  • Reducing abnormal development and growth of cells of the cervix (cervical dysplasia) caused by human papilloma virus (HPV) infection.
  • Low blood pressure. Green tea might help in elderly people who have low blood pressure after eating.

Possibly Ineffective for...

  • Preventing colon cancer.

Insufficient Evidence to Rate Effectiveness for...

  • Weight loss, high blood pressure, heart disease prevention, stroke prevention, osteoporosis, type 2 diabetes, skin cancer, breast cancer, lung cancer, stomach cancer, dental cavities, gingivitis, kidney stones, prostate cancer, diarrhea, chronic fatigue syndrome (CFS), and other conditions.

How does Green Tea work?

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. It also contains antioxidants and other substances that might help protect the heart and blood vessels.

Are there safety concerns?

Green tea is safe for most adults. Green tea extract seems to be 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.

Too much green tea, such as more than five cups per day, 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.

If you are pregnant or breastfeeding, green tea in small amounts is probably not harmful. 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 is probably safe in children in amounts commonly found in foods.

Avoid consuming large amounts of green tea if:

  • You are pregnant or breast-feeding.
  • You have a heart condition.
  • You have a liver disease.
  • You have severe anemia.
  • You have high blood pressure. Small amounts of green tea taken regularly do not seem to raise blood pressure, but blood pressure can be affected in someone who isn't used to the caffeine in green tea.
  • You have glaucoma.
  • You have anxiety disorder.

Are there any interactions with medications?



Amphetamines
Interaction Rating: Major Do not take this combination.

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
Interaction Rating: Major Do not take this combination.

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
Interaction Rating: Major Do not take this combination.

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)
Interaction Rating: Major Do not take this combination.

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).



Adenosine (Adenocard)
Interaction Rating: Moderate Be cautious with this combination.
Talk with your health provider.

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.



Antibiotics (Quinolone antibiotics)
Interaction Rating: Moderate Be cautious with this combination.
Talk with your health provider.

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).



Birth control pills (Contraceptive drugs)
Interaction Rating: Moderate Be cautious with this combination.
Talk with your health provider.

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)
Interaction Rating: Moderate Be cautious with this combination.
Talk with your health provider.

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)
Interaction Rating: Moderate Be cautious with this combination.
Talk with your health provider.

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)
Interaction Rating: Moderate Be cautious with this combination.
Talk with your health provider.

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)
Interaction Rating: Moderate Be cautious with this combination.
Talk with your health provider.

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 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)
Interaction Rating: Moderate Be cautious with this combination.
Talk with your health provider.

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
Interaction Rating: Moderate Be cautious with this combination.
Talk with your health provider.

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)
Interaction Rating: Moderate Be cautious with this combination.
Talk with your health provider.

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
Interaction Rating: Moderate Be cautious with this combination.
Talk with your health provider.

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 asthma (Beta-adrenergic agonists)
Interaction Rating: Moderate Be cautious with this combination.
Talk with your health provider.

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).



Medications for depression (MAOIs)
Interaction Rating: Moderate Be cautious with this combination.
Talk with your health provider.

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.



Medications moved by pumps in cells (Organic Anion-Transporting Polypeptide Substrates)
Interaction Rating: Moderate Be cautious with this combination.
Talk with your health provider.

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).



Medications that can harm the liver (Hepatotoxic drugs)
Interaction Rating: Moderate Be cautious with this combination.
Talk with your health provider.

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)
Interaction Rating: Moderate Be cautious with this combination.
Talk with your health provider.

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.



Medications used to treat cancer (Boronic acid-based proteasome inhibitors)
Interaction Rating: Moderate Be cautious with this combination.
Talk with your health provider.

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
Interaction Rating: Moderate Be cautious with this combination.
Talk with your health provider.

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)
Interaction Rating: Moderate Be cautious with this combination.
Talk with your health provider.

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



Phenylpropanolamine
Interaction Rating: Moderate Be cautious with this combination.
Talk with your health provider.

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)
Interaction Rating: Moderate Be cautious with this combination.
Talk with your health provider.

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.



Stimulant drugs
Interaction Rating: Moderate Be cautious with this combination.
Talk with your health provider.

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.



Theophylline
Interaction Rating: Moderate Be cautious with this combination.
Talk with your health provider.

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)
Interaction Rating: Moderate Be cautious with this combination.
Talk with your health provider.

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)
Interaction Rating: Moderate Be cautious with this combination.
Talk with your health provider.

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
Interaction Rating: Minor Be cautious with this combination.
Talk with your health provider.

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)
Interaction Rating: Minor Be cautious with this combination.
Talk with your health provider.

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 changed by the liver (Cytochrome P450 3A4 (CYP3A4) substrates)
Interaction Rating: Minor Be cautious with this combination.
Talk with your health provider.

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.



Medications for diabetes (Antidiabetes drugs)
Interaction Rating: Minor Be cautious with this combination.
Talk with your health provider.

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.



Mexiletine (Mexitil)
Interaction Rating: Minor Be cautious with this combination.
Talk with your health provider.

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)
Interaction Rating: Minor Be cautious with this combination.
Talk with your health provider.

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.



Terbinafine (Lamisil)
Interaction Rating: Minor Be cautious with this combination.
Talk with your health provider.

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.

Dosing considerations for Green Tea.

The following doses have been studied in scientific research:

AS A DRINK:
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.

APPLIED TO THE SKIN:

  • 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.
  • For genital warts: a specific green tea extract ointment (Veregen, Bradley Pharmaceuticals) providing 15% kunecatechins applied three times daily to external warts for up to 16 weeks has been used.

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