Antonietta M. Cerroni, Ph.D.
May 23, 2017
Green tea extract, a readily available “natural health product” (NHP), can have a devastating impact on liver function in people who are deficient in certain key enzymes, leading to toxicity, liver injury, liver failure and even death.
The Difference Between Green Tea and Green Tea Extract
Many people are not aware that green tea, a type of tea made from un-oxidized Camellia sinensis leaves, is very different from the “natural” health supplement known as “green tea extract”. The popular, steeped green tea is a beverage that contains catechins, a type of antioxidant (polyphenols). Green tea extract, however, is sold over-the-counter as a Health Canada-approved “weight-loss supplement”, which comes in the form of tablets, capsules, powders or liquids. Green tea extract also contains catechins, but at much higher concentrations. “Natural health products” such as green tea extract have been growing in popularity; in 2015, consumers spent about $140 million on such weight-loss supplements (Consumer Reports, Jan. 2017; data from Nutrition Business Journal).
For some people, green tea extract can be hazardous at high doses.
The ill effects of ingesting high concentrations of green tea extract have been known for some time, with several fatal cases of liver failure reported in the media. Health Canada began a safety review of green tea extract between 2016-09-01 and 2016-09-30, citing liver injury as a potential safety issue. Health Canada discloses a case of liver injury caused by green tea extract here. An investigation by CBC’s Marketplace found more than 60 documented cases worldwide, of liver failure associated with weight-loss supplements containing green tea extract, reported in the medical literature.
Some reports, such as a review published in 2009 on the findings of the Italian “surveillance system of natural health products”, noted an association between green tea and liver damage that could be “related to the patient’s metabolism” and also concluded that, in a few cases, “toxicity related to concomitant medications may also be involved”. It is known that many of the ingredients in health supplements have the potential to interact with prescription and over-the-counter medications; see a list here. Furthermore, experts also point out that there is no solid evidence proving that these so-called weight-loss supplements are effective, dubbing them “hope in a bottle”. Unlike prescription drugs, most “natural health products” (NHP) do not require clinical trials to demonstrate that they are safe and effective in order to be licensed by Health Canada.
Green tea extract was approved by Health Canada on April 18, 2008 as “a source of antioxidants for the maintenance of good health” and “to be used with a program of reduced intake of dietary calories and increased physical activity (if possible) to help in weight management”. Health Canada requires certain cautions and warnings on the packaging of green tea extract, recommending a consultation with a healthcare practitioner prior to use if you:
- have a liver disorder or develop symptoms of liver trouble (such as abdominal pain, dark urine or jaundice)
- are pregnant or breastfeeding
- have an iron deficiency
- intend to take it for more than 12 weeks
However, these recommendations do not go far enough…
Green Tea Extract and Cytochrome P450 genes
There are known interactions between green tea extract and the Cytochrome P450 genes – the same genes that are responsible for creating the liver enzymes that your body needs to break down medicines. Inherited differences in these enzymes affect how well your body is able to metabolize commonly prescribed medications.
CYP3A is the main drug metabolizing enzyme for green tea extract.
A study published in 2013 has shown that “green tea catechins cause clinically relevant interactions with substrates for CYP2B6 and CYP2C8 in addition to CYP3A”. People who are deficient in CYP2B6, CYP2C8 or CYP3A enzymes may be at a higher risk of sustaining liver damage. GeneYouIn’s experience has shown that people with inherited deficiency in two of these enzymes are at a higher risk of liver or kidney failure due to the body’s reduced capacity for detoxification.
Natural health products may not always be “benign” or “beneficial”; it depends on the person’s ability to metabolize the active ingredients in such products – and this is true for green tea extract. Before starting any treatment regimen, even one involving natural health products, it is important to ask questions and obtain advice from your healthcare practitioner. A pharmacogenetic test may be recommended before initiating treatment, in order to find out whether or not your liver enzymes are functioning optimally.
The Pillcheck drug response test reveals the activity levels of the Cytochrome P450 enzymes and predicts your response to over 100 commonly prescribed medications, using markers that include the unique variations that reflect the multi-ethnic nature of Canadian society.
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Read more here:
Misaka S, Kawabe K, Onoue S, Werba JP, Giroli M, Tamaki S, Kan T, Kimura J, Watanabe H, Yamada S. Effects of green tea catechins on cytochrome P450 2B6, 2C8, 2C19, 2D6 and 3A activities in human liver and intestinal microsomes. Drug Metab Pharmacokinet. 2013;28(3):244-9. Epub 2012 Dec 25.
Mazzanti G, Menniti-Ippolito F, Moro PA, Cassetti F, Raschetti R, Santuccio C, Mastrangelo S.
Hepatotoxicity from green tea: a review of the literature and two unpublished cases. Eur J Clin Pharmacol. 2009 Apr;65(4):331-41. Epub 2009 Feb 6.