Green tea

• Uses
• Benefits
• Cautions
• Interactions
• References

Uses

• Prevent various cancers, including breastcancer, prostatecancer, coloncancer, gastric cancer, lung cancer, solid tumor cancers and skin cancer related to exposure to sunlight
• To fight human papilloma virus (HPV), which can cause genital warts, the growth of abnormal cells in the cervix (cervical dysplasia), and cervical cancer.
• Crohn’s disease
• Parkinson’s disease
• Diseases of the heart and blood vessels
• Diabetes
• Low blood pressure
• Chronic fatigue syndrome (CFS)
• Dental cavities (caries)
• Kidney stones
• 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.
• Genital warts: A specific green tea extract ointment (Veregen, Bradley Pharmaceuticals) is FDA-approved for treating genital warts.
• High cholesterol: Taking green tea by mouth seems to lower cholesterol levels. Research suggests that consuming 145-3000 mg of green tea catechins, an antioxidants found in green tea, daily for up to 24 weeks reduces total cholesterol and low-density lipoprotein (LDL or “bad”) cholesterol.
• Mental alertness: Drinking green tea and other caffeinated beverages seems to help people maintain mental alertness throughout the day. Combining caffeine with sugar as an “energy drink” seems to improve mental performance more than caffeine or sugar alone. Also, taking a combination of green tea extract and L-theanine for seems to improve memory and attention in people with mild mental problems.
• Abnormal development of cells of the cervix (cervical dysplasia): Taking green tea by mouth or applying it to the skin seems to reduce cervical dysplasia caused by human papilloma virus (HPV) infection.
• ‘Clogged arteries (coronary artery disease): Population studies suggest that drinking green tea is linked to a reduced risk of clogged arteries. The link seems to be stronger in men than women.
• Endometrial cancer. Population studies suggest that drinking green tea is linked to a reduced risk of developing endometrial cancer.
• Low blood pressure: Drinking green tea might help increase blood pressure in elderly people who have low blood pressure after eating.
• Thick, white patches on the gums (oral leukoplakia): Drinking green tea seems to decrease the size of white patches in people with oral leukoplakia.
• Osteoporosis: Research suggests that drinking green tea for 10 years is linked to increased bone mineral density. Also, early research suggests that taking a green tea compound containing 500 mg of catechins, an antioxidant in green tea, daily for 24 weeks improves bone strength in post-menopausal women with low bone density.
• Ovarian cancer: Women who regularly drink tea, including green or black tea, appear to have a lower risk of developing ovarian cancer.
• Parkinson’s disease: Drinking one to four cups of green tea daily seems to provide the most protection against developing Parkinson’s disease.

Benefits

• 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.

Cautions

• Green tea is LIKELY SAFE for most adults when consumed in moderate amounts. Green tea extract is POSSIBLY SAFE for most people when taken by mouth or applied to the skin for a short time. In some people, green tea can cause stomach upset and constipation. Green tea extracts have been reported to cause liver problems in rare cases.
• Drinking 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 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.
• 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. Also, 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.
• 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.

Interactions

Major Interaction – Do NOT take this combination

• Amphetamines: interacts with green tea Do not take together. 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.

Moderate InteractionBe cautious with this combination

• Adenosine (Adenocard): 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): 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): 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.

• 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 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): 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: 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): 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 for depression (MAOIs) 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): 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): 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: 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.

• 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, 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: 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 Interaction – Be watchful with this combination

• 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.

• Medications for diabetes (Antidiabetes drugs): 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): 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): 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.

References

Source: WebMD, “Green Tea”, www.webmd.com/vitamins-supplements/