Green tea features not just a pleasant, mild flavor, but is also an antioxidant-rich product. These cancer-fighting agents, extracted from the tea's leaves and then placed in capsules, may have raised the eyebrows of some skeptics, because its safety as an extract was called into question. Studies followed and produced some interesting results.
About Green Tea
Green tea, a favorite beverage in Asian countries, comes from the plant Camellia sinensis. It has many marketed names, including Camellia thea, Camellia theifera, epigallo catechin gallate or EGCG, green sencha tea, green polyphenolic fraction or GTPF and many others, according to Rxlist.com. Claims of its many medical uses abound, some proven, some not. Some evidence does exist that drinking green tea can lower cholesterol, help prevent Parkinson's disease and help prevent certain cancers such as bladder, esophageal and pancreatic.
Safety Concerns
While green tea proves safe for most adults, the tea extract has caused liver problems. Further, taking extract in excess of more than the equivalent of five cups of green tea a day may cause dizziness, irritability, palpitations, nervousness, vomiting, diarrhea, tremor, heartburn, ringing in the ears, insomnia, confusion and convulsions. Attributed to its caffeine content, these side effects have a direct relationship to the amount consumed. The possibility also exists that green tea interferes with the body's absorption of iron. These side effects occur with all green tea products, but only the extract has been associated with liver problems.
Studies
After the removal of green tea from the French and Spanish markets because of concerns about liver toxicity, the U.S. Pharmacopeia, or USP, had its dietary supplement committee review the safety information of green-tea products, according to the National Institutes of Health. The committee's review of green tea extract noted new information. According to USP.org, the tea's monograph, the statement of the supplement's use, safety and contraindications, was re-evaluated and redefined. This led to a new classification of green-tea extract that requires it to have cautionary labeling.
Contraindications
Pregnant or breast-feeding women should avoid large amounts of green tea and its extract. If you have a heart condition, liver disease, severe anemia, glaucoma or anxiety disorder, do not take green tea in any form. The caffeine in green tea can raise blood pressure. If you have hypertension and don't normally consume products with caffeine, avoid green tea.
Medication Interactions
Do not consume any form of green tea with amphetamines, cocaine or ephedrine. RxList.com reports the caffeine in green tea and green tea extract supplements can equally compound the effects of these nervous-system stimulants and result in increased heart rate, high blood pressure and possibly stroke. Those drugs that have moderate interactions with green tea include adenosine, quinolone antibiotics, birth-control pills, bortezomib, cimetidine, clozapine, dipyridamole, dislulfiram, estrogens, fluvoxamine and lithium. Also, if you take any drugs that in themselves can harm the liver or slow blood clotting, you should not take them concurrently with green tea extract because concurrent use increases chances of liver problems. Certain cancer drugs and nicotine, pentobarbital, phenylpropanolamine, riluzole, theophylline, verapamil and warfarin have a moderate interaction with green tea products. Medications that have a mild interaction include anti-diabetic drugs mexiletine and terbinafine.
Green Tea Product Use
The side effects of green tea stem from its caffeine content whether in drink or extract form. The disadvantage of taking green tea extract is that besides the side effects of its caffeine, it may harm the liver, especially when taking medications that also involve this risk. Drinking decaffeinated green tea may hold the most promise for safety and health benefits. In supplement form, extract makes a good standby for times when you run out of the drink form. Regardless of how you take green tea products, limit your intake to less than five cups a day for caffeinated tea and the equivalent amount in capsule form.
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