Green Tea ExtractsFor the last decades, the army of true green tea lovers has become really huge. I guess, we all know everything about numerous curative properties and therapeutic effects of green tea. The benefits of this miraculous herb are associated with longevity, cancer-free and diabetes-free life, perfect skin and absence of tooth cavities, low cholesterol levels and effective weight management, lower risks of having problems with the function of cardio-vascular and digestive systems. However, consuming something, even very useful and therapeutic, in large quantities will not do anything good to us. Therefore, doctors warn us about harmful effects of taking too much of even such beneficial herbal remedy as green tea.

Joshua D. Lambert and Chung Yang of Rutgers, the State University of New Jersey, worked on reviewing the known curative properties of green tea. However, soon they got concentrated on studying green tea harmful side effects and the dangers connected with green tea overdosing. The specialists have had an experience on this subject before: during his earlier research, Joshua Lambert found out that great amounts of antioxidants in green tea can cause kidney damage, liver toxicity and serious oxidative stresses (Lambert, J.D., et al., (2007) Possible Controversy over Dietary Polyphenols: Benefits vs Risks, Chem Res Toxicol).

A lot of alarming information came out. A group of American specialists at Toxicology Research Laboratory, University of Illinois Chicago, carried out a series of experiments with dogs, aiming on studying the effects of exposure to green tea extracts. Severe intoxication, body organ damage and mortality of the animals made the Green Tea Harmful Side Effectsscientists terminate their experiments much earlier (Toxicology, 2009 Jun 16; 260(1-3):28-36). Finally, the results of these studies were confirmed by another famous specialist H.L. Bonkovsky, who recorded hepatoxisity in people associated with polyphenols in green tea (published in Journal of Hepatology).

In addition to all this, the experts from a scientific lab in the University of Mississippi published the findings of their new study. They say that green tea overdose may lead to increased tumor growth. The mentioned green tea harmful side effects can be observed only when consuming this herbal remedy in really high doses, but low doses are usually associated with the property to suppress tumor development and growth. Read more about this study in the Journal of Natural Products.

Actually, the researchers underline that drinking up to 10 small cups of green tea a day is not connected with any serious danger. But taking green tea supplements which have increased amounts of polyphenols is linked to the mentioned health problems. “Problems are likely in people who take supplements, which can contain up to 50 times as much polyphenols as a single cup of tea,” Professor Young comments. Thus, we should be really cautious while taking products containing green tea extracts. Those who are interested can read more about this interesting summarizing research in Chemical Research in Toxicology, vol 20, p 583-585.

Author Info: Hi! My name is Carla and I am a 5th year medical student at HYMS. I am interested in alternative medicine and I have done months researching the topic of herbal medicine. Besides, I like interviewing people and learning more about their experiences with one or another type of herbal treatments. I am willing to contribute to this site with my knowledge, and I would be happy to help you out to the best of my ability with any specific questions or problems related to alternative medicine.

4 Responses to “Too Much Green Tea Can Be Harmful”

  1. vamsi krishnaNo Gravatar Says:

    Dear Carla,
    I am a green tea lover. I would like to know whether there are serious side effects for girls whose menstrual cycle is irregular and they consume green tea.I have heard that green tea consumption leads to lowering of estrogen hormone.

  2. RoshniNo Gravatar Says:

    Hi Carla, Have you heard of ‘Tea tonic’ range. They have a lot of varieties like complexion tea, wellness, relaxation etc., That tea range is said to have developed by a naturopath.

    Do you have any comments on that?

  3. LoreeNo Gravatar Says:


    I consume approx. 6 cups of green tea daily (2 soup cups).

    I’ve just began taking a liquid multivitamin- Nature’s Plus Source of Life Liquid Multi-Vitamin & Mineral Supplement- and am wondering if my health conscious choices have the potential to be hazardous to my health.

    What is considered a polyphenol? I’d like to compare it to the product label on my multi-vitamin.


  4. EVONNE MPSONNo Gravatar Says:

    HOW MUCH TEA IS TOO MUCH. How many ounces?
    PLease let me know.