Green Tea: Panacea or Poison?


In the news: a woman in Fort Wayne, Indiana is suing the Arbonne International company in Allen Superior Court, claiming that its product contained toxic levels of green tea extracts, causing her to develop acute liver failure.

Green tea accounts for 20% of tea consumption worldwide. It has become more and more popular because of its many reported health benefits; the consumption of green tea in the US has risen by 40% just since 2000. A less-processed form of tea, green tea contains higher levels of antioxidants and polyphenols than other teas. It was traditionally used to control bleeding, heal wounds, aid digestion, improve heart and mental health and regulate body temperature. More recently, research has suggested that it has many health benefits.

The evidence for health benefits

The University of Maryland Medical Center has a helpful webpage that summarizes all the relevant research and provides a long list of references. Green tea may reduce the risk of heart disease (but the FDA prohibits that claim on labels; they concluded there was no credible evidence to support it). Green tea lowers total cholesterol and raises HDL. Population studies suggest that it may help protect against several kinds of cancer, but the evidence is mixed: other studies suggest that it may actually increase the risk of some cancers, and it may interfere with cancer chemotherapy. It may help in inflammatory bowel disease, diabetes, liver disease, and weight loss. There is even preliminary evidence that it might prevent dental cavities, might be useful in arthritis, might help treat genital warts, and might even prevent symptoms of colds and flu. Studies show that drinking green tea is associated with reduced risk of dying from any cause. At first glance, it might sound like a panacea, but the evidence is still questionable. Much of it is from small, preliminary studies that have not been replicated or that contradict each other.

The Natural Medicines Comprehensive Database does not rate green tea as “effective” for any indication. It rates green tea as “likely effective” only for genital warts, lyperlipidemia, and mental alertness (because it contains caffeine?). It rates it as “possibly effective” for cervical dysplasia, coronary artery disease, endometrial cancer, hypotension, oral leukoplakia, osteoporosis, ovarian cancer, and Parkinson’s disease. It concludes that there is insufficient reliable evidence to rate its effectiveness in acne, amyloidosis, athletic performance, bladder cancer, esophageal, cancer, pancreatic cancer, breast cancer, cardiovascular disease, colds and flu, colorectal cancer, diabetes, fertility, gastric cancer, hypertension, Japanese cedar pollinosis, leukemia, lung cancer, metabolic syndrome, obesity, oral cancer, periodontal disease, pneumonia, prostate cancer, stress, stroke, upper respiratory infection, or wrinkled skin.


The Natural Medicines Comprehensive Database gives green tea a rating of “likely safe” when used as a beverage in moderate amounts, as “possibly safe” when used as an extract for up to 6 months, as “possibly unsafe” for long-term use in high doses due to its caffeine content, and as “likely unsafe” when used orally in very high doses. It reports a long list of adverse reactions including liver failure. It reports a long list of interactions with other supplements and with drugs, and warns that green tea may worsen symptoms of various diseases.

The Arbonne lawsuit

There is emerging evidence to suggest that green tea can cause liver damage. The woman who is suing Arbonne, Vicki Swanson, bought the company’s “30-Day Feeling Fit Kit,” because it promised to “take the guesswork out of getting fit.” After about 6 weeks, she developed lethargy and jaundice. She was hospitalized and diagnosed with acute liver failure caused by toxic levels of green tea extracts. She had no history of liver disease and no other source of green tea. Her lawsuit accuses Arbonne of selling a dangerous and defective product, breaching its warranties, and negligence.

Arbonne International is a multilevel marketing company that sells herbal-based skincare, beauty, and wellness products. The “30-Day Feeling Fit Kit” is also sold on the Amazon website. For $265.97 (marked down from list price $299) + $10.49 shipping, you get “protein shakes mixes, energy fizz sticks, fit chews, chocolate, herbal detox, and fiber boost.” I was unable to find out how much green tea is in the products.

Evidence for liver toxicity

Concerns about safety developed as early as 2003, when a green tea weight-loss supplement was withdrawn from the market in France after it was blamed for 13 cases of liver toxicity. In 2009 the FDA warned consumers to stop using Hydroxycut products because of the risk of liver injury.

An April, 2015 article in the Archives of Toxicology reviewed the evidence for the liver toxicity of green tea-based herbal supplements. The same authors had earlier written a review of the literature published between 1999 and 2008, identifying 34 cases of liver damage from green tea, with one death and with positive re-challenge tests confirming causation in 20% of cases. In this new study, they surveyed more recent evidence from studies published between 2008 and March 2015. They found a probable causal link in 8 cases of liver damage and a possible causal link in 11 other cases. They used stringent criteria to determine causation, ruling out other causes of liver damage such as viral hepatitis and alcohol abuse. 12 of the 19 reactions involved patients who took multicomponent (MC) preparations. All cases required hospitalization. The reactions from MC preparations had a quicker onset (mean: 44.7 days) and were more serious, requiring liver transplantation in four cases. Recovery occurred mainly between 20 and 90 days, but took as long as 540 days and sometimes treatment with corticosteroids was required to obtain resolution. MC preparations may contain other ingredients that enhance the risk, and it is difficult to ascribe the toxicity to one component. The patients who took only green tea consumed as little as two cups to as much as three liters daily. Considering the vast numbers of people who have used green tea supplements or who drink tea, the quantitative risk is very small.

A systematic review of the safety of green tea extracts by the U.S. Pharmacopeia (a nonprofit standards-setting organization) was published in Drug Safety in 2008.

They analyzed 216 case reports on green tea products and found 34 reports of liver damage. They categorized 27 of these as possible causality and 7 as probable. They were concerned that they might only be seeing the tip of the iceberg. An FDA-commissioned study showed that the FDA only receives <1% of all adverse event reports associated with dietary supplements. The authors of that study commented that (thanks to the DSHEA):

for dietary supplements, vital premarket information (which is available for drug products) is often missing so that possible public health concerns generated by the adverse event reporting system, such as limited clinical information, product identification, and information on consumer use, cannot be adequately assessed.

The benefits and risks of polyphenols

In a 2007 article in Chemical Research in Toxicology, the authors reviewed the evidence for benefits and risks of polyphenols, the major component of green tea. They concluded:

Although consumption of dietary phytochemicals such as flavonoids has been suggested to have beneficial biological effects including the prevention of cancer and heart disease, there is considerable evidence to suggest that such compounds are not without risk of adverse effects. The risk of adverse effects is likely increased by the use of pharmacological doses in prevention/treatment and supplement situations and genetic polymorphisms or drug−drug interactions that increase the bioavailability of test compounds. Such situations should be the subject of extensive future animal studies. A clear understanding of the potential adverse effects of dietary phytochemicals, including polyphenols, is necessary. Only when such data are compared to the evidence for beneficial health effects can a balanced judgment be made regarding the potential utility of these compounds for disease prevention and treatment.


So where do we stand? Even if Ms. Swanson wins her lawsuit, that wouldn’t constitute proof of causation. We don’t have any direct, incontrovertible evidence that green tea can cause liver failure, but we have good enough evidence to suspect that it can. On the other hand, neither do we have any really compelling evidence that it has the many health benefits claimed for it. Further research will be needed to better understand the risk/benefit ratio. In my opinion, a cautious approach to green tea supplements is indicated, but there is no reason to avoid drinking green tea as a beverage in moderate amounts if you enjoy the taste.

This article was originally published in the Science-Based Medicine Blog.

Dr. Hall is a contributing editor to both Skeptic magazine and the Skeptical Inquirer. She is a weekly contributor to the Science-Based Medicine Blog and is one of its editors. She has also contributed to Quackwatch and to a number of other respected journals and publications. She is the author of Women Aren’t Supposed to Fly: The Memoirs of a Female Flight Surgeon and co-author of the textbook, Consumer Health: A Guide to Intelligent Decisions.

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