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Green Tea: Precautions & Interaction Information - The use of herbs is a time-honored approach to strengthening the body and treating disease. People with these issues should consult a physician before drinking tea:

Green tea can also interact with the following drups. Consult a healthcare provider before mixing green tea with the following:

A cup of green tea contains about half the amount of caffeine as a cup of coffee. It also contains theanine which acts as a relaxant to counter caffeine's stimulative effects. 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.
Condition Guide
Pregnancy and Breast Feeding - Pregnant women would be wise to limit the amount of green tea they drink during pregnancy, and should be careful about taking any green tea supplements. Green tea is rich in antioxidants
and has a hostof health benefits relating to dental health, blood sugar levels, cholesterol, and weight loss. But researchers have found, whilst examining the active constituent of green tea, the epigallocatechins, or EGCG for short, that it may affect the way the body uses folate. Folate is important for pregnant women as it prevents neural tube birth defects in babies. The good news on caffeine drank during pregnancy, from coffee and tea, is that a moderate amount is fine. Two studies, one by Danish scientists who interviewed more than 88,000 pregnant women, and the other by the Yale University School of Medicine, had similar findings on caffeine during pregnancy.
Heart Problems - Green tea has been shown to have a variety of benefits for the heart. The main issue around avoiding it for these conditions is the amount of natural caffeine in the which can raise blood pressure.
As with most negative side effects attributed to green tea their are balancing positive effects. According to one study, drinking one or more cups of tea can almost halve the risk of heart attack (Sesso et al. 1999). Green tea contains a much higher concentration of theanine than other teas. Theanine has been proven to lower blood pressure (Abe et al. 1995; Yokogoshi et al. 1995; Yokogoshi et al. 1998a). It works through its GABA enhancing effects. Along with its calming effect on the brain, GABA also lowers blood pressure.
Kidney Disorders - If you suffer from or are prone to developing kidney stones, you may have a dilemma whether to drink tea. Kidney stones are mineral deposits made up of calcium, uric acid or the amino acid cysteine. At least 3
quarters of kidney stones are composed of calcium combined with phosphate or oxalic acid.Tea is a concern because it is rich in oxalic acid. To put it in perspective, there are other foods rich in oxalic acids, such as beet greens, chocolate, rhubarb, spinach, and sorrel. If you do eat these foods, avoid paring them with another food high in calcium, such as spinach and cheese or chocolate and milk. A 1998 American study published in the April edition of the Annals of Internal Medicine found that drinking tea reduces kidney stones risk in women. Green tea contains catechins. They act as powerful antioxidants, wiping out free radicals that can form urinary stones. A 2005 study conducted by Nagoya City University Graduate School of Medical Sciences found that laboratory rats drinking green tea were less likely to develop stones in the urinary tract. This study was confirmed by a separate 2006 study conducted by Seoul National University. In both green tea and kidney stones studies, the scientists believed that green tea antioxidants inhibit the formation of urinary stones. The probability of tea causing kidney stones can be dramatically reduced by ingesting some form of calcium along with the tea in order to form the calcium oxalate in the digestive tract (where it cannot be absorbed and will pass through), rather than in the bloodstream or the kidney.

If you have Kidney Disease avoid drinking teas with too much caffeine, such as darjeeling, assam and other types of black tea. White and green tea are typically lower in caffeine and also have corresponding beneficial effects. You don't need to put any sugar in these types of teas because they are not very astringent.
Anxiety Disorder - Again the issues has to do with caffeine in green tea raising anxiety levels. However there is a counterbalancing ingredient in green tea. An amino acid known as L-Theanine. Researchers in
Japan have discovered that theanine is a caffeine antagonist, meaning that it offsets the "hyper" effect of caffeine (Kakuda et al. 2000). That is why many people will have a "soothing" cup of tea and not a soothing cup of coffee. Theanine does not cause drowsiness like kava kava, nor does it interfere with the ability to think clearly like prescription tranquilizers.There is evidence that tea exerts far more than just a psychological effect. According to one study, drinking one or more cups of tea can almost halve the risk of heart attack (Sesso et al. 1999). Green tea contains a much higher concentration of theanine than other teas. Theanine has been proven to lower blood pressure (Abe et al. 1995; Yokogoshi et al. 1995; Yokogoshi et al. 1998a). It works through its GABA enhancing effects. Along with its calming effect on the brain, GABA also lowers blood pressure.
Flouride - Tea has naturally high fluoride levels. Excess fluoride can weaken bones and discolor children's un-erupted teeth. According to Cao et al. in a tea and fluoride study published in Food Chemistry, 4 cups of tea delivered 0.8 to
1.8 mg of fluoride. Among populations habitually consuming black tea, water fluoridation is not only unnecessary but also possibly harmful...The target organs of chronic fluoride intoxication are not only the teeth and skeleton, but also the liver, kidney, nervous and reproductive systems. A March 2008 tea and fluoride study published in Food and Chemical Toxicology found up to 4.5, 1.8, and 0.5 mg/L fluoride in black, green and white teas, respectively, when brewed for 5 minutes. 61 teas were included in the sample. According to 1997 ADA data, 3 and 4 milligrams daily are adequate for women and men, respectively, to prevent fluoride's adverse effects. It is much lower for children. In 2006, the National Research Council reported the basis for those levels should be reduced. Fluoride content is measured in parts per million (ppm). 1 ppm is equivalent to 1 milligram of fluoride in 1 litre of water. In the United States, drinking water can contain up to a maximum of 4 parts per million (ppm). Choose green tea over black tea. Brewed black tea has 3.7 ppm, whereas green tea has only 1.2 ppm. Avoid highly processed tea. Instant tea powder with lemon and sugar has 5.8 ppm. Decaffeinated green tea has 2.7 ppm.
Drug Interaction Guide
Adenosine - Green tea may inhibit the actions of adenosine, a medication given in the hospital for an irregular (and usually unstable) heart rhythm.
Antibiotics (Beta-lactam) - Green tea may increase the effectiveness of beta-lactam antibiotics by reducing bacterial resistance to treatment.
Benzodiazepine - Caffeine (including caffeine from green tea) has been shown to reduce the sedative effects of benzodiazepines (medications commonly used to treat anxiety, such as diazepam and lorazepam).

Beta-blockers, Propranolol, & Metoprolol - Caffeine (including caffeine from green tea) may increase blood pressure in people taking propranolol and metoprolol medications to treat high blood pressure/heart disease).
Blood Thinning Medications (Incl. Aspirin) - It is important to be aware of foods that are particularly high in vitamin K if you are taking prescription anticoagulants. People who take warfarin, a blood thinning medication,
should consult a physician about drinking green tea since it does contain vitamin K. Vitamin K can make warfarin ineffective. Dried green tea leaves have a very high concentration of vitamin K, but a cup of brewed green tea provides only a small amount, 0.03 mcg per 3.5 fluid ounces (roughly half a cup). Research published in the Journal of the American Dietetic Association in 1995 showed that tea is not a significant dietary source of vitamin K. Exercise caution mixing green tea and aspirin because they both prevent platelets from clotting. Using the two together may increase your risk of bleeding.

Chemotherapy - The combination of green tea and chemotherapy meds, specifically doxorubicin and tamoxifen, increased the effectiveness of these medications in laboratory tests.
However, these results have not yet been demonstrated in studies on people. There have been reports of both green and black tea extracts stimulating a gene in prostate cancer cells that may cause them 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 for prostate cancer in particular.

Studies indicate Green tea polyphenols block the anticancer effects of bortezomib and other boronic acid-based proteasome inhibitors. Bortezomib (Velcade®) is a proteasome inhibitor in clinical use for multiple myeloma. It was discovered that various green tea constituents effectively prevented tumor cell death induced by bortezomib in vitro and in vivo. This pronounced antagonistic function of EGCG was only evident with boronic acid-based proteasome inhibitors (bortezomib, MG-262, PS-IX), but not with several non-boronic acid proteasome inhibitors (MG-132, PS-I, nelfinavir). EGCG directly reacted with bortezomib and blocked its proteasome inhibitory function; as a consequence, bortezomib did not induce tumor cell death. Taken together, results indicate that green tea polyphenols may have the potential to negate the therapeutic efficacy of bortezomib and consumption of green tea products may be contraindicated during cancer therapy with bortezomib.
Clozapine - The anti- psychotic effects of the medication clozapine may be reduced if taken fewer than 40 minutes after drinking green tea.
Ephedrine - When taken together with ephedrine, green tea may cause agitation, tremors, insomnia, and weight loss.
Lithium - Green tea has been shown to reduce blood levels of lithium (a medication used to treat manic/depression).
Monoamine Oxidase Inhibitors (MAOIs) - Green tea may cause a severe increase in blood pressure (called a "hypertensive crisis") when taken together with MAOIs, which are used to treat depression. Examples of
MAOIs include phenelzine and tranylcypromine.
Oral Contraceptives - Oral contraceptives can prolong the amount of time caffeine stays in the body and may increase its stimulating effects.
Phenylpropanolamine - A combination of caffeine (including caffeine from green tea) and phenylpropanolamine (an ingredient used in many over-the-counter and prescription cough and cold medications and weight loss
products) can cause mania and a severe increase in blood pressure. The FDA issued a public health advisory in November 2000 to warn people of the risk of bleeding in the brain from use of this medication and has strongly urged all manufacturers of this drug to remove it from the market.
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