Green tea is produced from the leaves of the Camellia sinesi tree, the same tree used to produce black tea. The difference between green and black tea is that the leaves are fermented to produce black tea but are left unfermented to produce green tea. Because the tea leaves are not fermented, they contain higher levels of antioxidants called polyphenols, which may have several health benefits. Green tea is generally safe and well-tolerated, although drinking more than five cups per day may lead to side effects, such as diarrhea, warns MedlinePlus.
Diarrhea
Some of the polyphenol compounds found in green tea, such as tannins and chlorogenic acid, can cause gastrointestinal irritations if consumed in large amounts. Additionally, green tea contains caffeine, and large doses of caffeine can also irritate the gastrointestinal system. As a result, drinking too much green tea can irritate the bowels and lead to diarrhea.
Additional Side Effects
Drinking excess amounts of green tea can cause a variety of other side effects, largely due to the caffeine content. Additional gastrointestinal side effects may develop, such as nausea, vomiting, heartburn and appetite loss. Dizziness, headache, irritability, insomnia, tremors and a ringing noise in the ears are also possible side effects. High amounts of caffeine can also affect the heart, causing heart palpitations or an irregular heartbeat.
Drug Interactions
Consuming too much green tea can possibly cause interactions with a variety of medications and other substances. Green tea may reduce the effectiveness of several medications, including benzodiazepines, adenosine, clozapine, lithium and blood-thinning medications such as warfarin. Other medications may interact with green tea to cause side effects, such as ephedrine, monoamine oxidase inhibitors, and phenylpropanolamine. Additionally, stimulants, such as nicotine, theophylline, cocaine and amphetamines, can interact with the caffeine in green and over-stimulate the nervous system, causing symptoms of mania, high blood pressure and rapid heartbeat.
Health Conditions
Certain health conditions can be exacerbated by drinking too much green tea, again mostly because of the caffeine. If you have stomach ulcers, kidney problems, heart disease or psychological disorders, such as anxiety, you should consult your doctor before drinking green tea. Large amounts of green tea may also affect blood sugar levels and cause complications for people with diabetes. Green tea may also worsen the symptoms of glaucoma, high blood pressure, liver disease and osteoporosis.
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