Possible Toxicity of Green Tea Extract

There are reports of possible liver toxicity with high doses of green tea extract (GTE), and since I’ve discussed GTE on this site, I felt I should address the issue of the possible toxicity of green tea extract here also.

The report mentions “dozens of cases” since 1999, and also that they’re caused by “high doses”, so given the huge number of people who have taken it for the past 18 years, the potential for toxicity is probably low. However, we can’t be sure.

The National Library of Medicine states:

Drinking green tea has not been associated with liver injury or serum aminotransferase elevations; indeed, cross sectional studies suggest that heavy use of green tea is associated with lower serum ALT and AST values.  Nevertheless, case series and a systematic review by the United States Pharmacopeia illustrate evidence for the potential for green tea extract to cause hepatotoxicity.  The prevalence of green tea extract induced liver injury is not known, but is probably low in comparison to the wide scale use of these products.  Liver injury typically arises within 3 months, with latency to onset of symptoms ranging from 10 days to 7 months.  The majority of cases present with an acute hepatitis-like syndrome and a markedly hepatocellular pattern of serum enzyme elevations.  Most patients recover rapidly upon stopping the extract or HDS, although fatal instances of acute liver failure have been described.  Biopsy findings show necrosis, inflammation, and eosinophils in a pattern resembling acute hepatitis.  Immunoallergic and autoimmune features are usually absent.  A small number of similar cases have also been described after drinking green tea “infusions” rather than taking oral preparations of extracts of green tea. 

The most prominent regulatory action against green tea containing products concerned Exolise, a weight loss product which was withdrawn from Spain and France in 2003.  Also, green tea is an ingredient in other supplements including most over-the-counter weight loss agents, some of which have been implicated in causing rare instances of clinically apparent acute liver injury.

While instances of liver injury appear to be rare, given the severity of liver injury, it may not be a good idea to take green tea extract.

I’ve taken green tea extract myself, but will now be stopping.


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Possible Toxicity of Green Tea Extract says March 25, 2017

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Antonio says March 25, 2017

I don`t buy this one.
Is EGCG a chelator of something? In that case jaundice could be the result of a heavy detox process. So go slowly at first.
At lest they acknowledge:
“Because Hydroxycut, like many dietary supplements, is a brand of many products with many ingredients, it is difficult to implicate a specific ingredient of the product as the cause for liver injury. Other listed components of Hydroxycut included calcium, chromium, potassium Garcinia cambogia, Gymnema sylvestre leaf extract, glucomannan, alpha-lipoic acid, willow bark extract, L-carnitine, caffeine, guarana extract, gelatin, silica and cellulose.”

Best regards.

    P. D. Mangan says March 26, 2017

    Hi Antonio, I agree it’s hard to get excited about htis. I came across a study of the catechin content of different brands of green tea, plus one green tea extract supplement. The total catechin content of Celestial Seasonings Green Tea, the brand with the highest amount of catechins, was 216 mg/100 ml, while that of a green tea extract capsule, made by Pharmanex, was less, at 205.

      Herman Rutner says March 26, 2017

      I agree consuming green tea extract as powder ought to be avoided . One reputable supplier recommends taking about 400 mg of 50% powder extract or 200 mg polyphenols, 1 to 3 x daily, for no more than 3 months! This amount would be equal to about 1 to about 5 cups of some Japanese green tea brands safe for daily consumption apparently without risking liver damage, at least in Japanese tea drinkers.

Lamm says March 26, 2017

While this is old news, it’s also a good reminder that the supplement industry is pretty much wild, wild west with no oversight, control or liability. Readers of this site probably know that but it still comes as a surprise to some.

http://www.pbs.org/wgbh/frontline/film/supplements-and-safety/ from what I remember is a good documentary on the issue.

Rob H says March 26, 2017

Hi Dennis, that’s a very thought-provoking post – I currently take 450mg of GTE every morning, and got my mother and wife doing the same.. One part of me says actually how much is this really an issue since firstly we have been taking it for longer than 10 months, so according to the article we should have experienced jaundice/ vomiting and other symptoms by now which we haven’t done.. Also, there was a follow-up article to the initial one you linked to which seems to be saying that GTE supps are mainly safe: http://mobile.nutraingredients-usa.com/Research/Review-supports-safety-of-green-tea-extracts

BUT, having read the detail of that first article it really does sound rather worrying that it might be damaging the liver in some way, and I am not comfortable with running that risk either for myself or for my wife and mother who are placing their trust in me to get this right! So, like you I think I will very grudgingly err on the side of caution for now and cease taking them for the time being. Or still toying with the idea of taking them every other day on fast mornings (but then just read one article which mentioned that the liver is particularly sensitive to the effects of GTE whilst in a fasted state..) We do drink green tea throughout the day too though, so will still be getting the benefit of that if we do cut out the GTE supplements altogether.

I was wondering though, what would you recommend to sub-in to the regime to replace the GTE, ie something else that works on a similar pathway? I am planning to introduce grapeseed extract instead for the 3 of us: one 100mg capsule every morning – what do you think of that as a strategy? That does raise one other potential risk though – would other hormetics such as grapeseed extract then pose similar risks to GTE? Are combining different hormetics together going to increase the potential risk? What’s a guy to do??! Any advice would be gratefully accepted as ever!

    P. D. Mangan says March 26, 2017

    Hi Rob, I think grape seed extract may substitute nicely: activates AMPK, etc. You could still drink a cup of green tea now and then too. I’d thought about writing something about Japanese matcha – one report states that it has 137 times as much catechins and Chinese green tea; but if catechins in GTE are the cause of liver injury, it’s hard to see why matcha wouldn’t be capable of it also. According to the reports, they believe that the cause of liver injury is high doses of epicatechin, so grape seed extract wouldn’t appear to bear any risk, at low doses anyway. Since I take berberine, resveratrol, and occasional curcumin, and plan to continue to drink green tea once in a while, i doubt I’ll miss any health benefits of GTE.

    PS: Here’s an article that says that only 1 cup of green tea daily massively lowers cancer risk.

      Rob H says March 27, 2017

      Thanks for your advice on that Dennis. Actually, when I step back and look at the big picture, then just because hormetic components have been shown to be beneficial when consumed as part of food, it does not logically follow that isolating out the specific hormetic components and then ingesting them as concentrated supplements would necessarily be beneficial. After all, we have only recently learned the same lesson with antioxidants so why wouldn’t the same lesson hold true for the hormetics too? I have to say, it does make me question the validity of taking any concentrated extract, even the grapeseed extract, but I’ll go along with that one for now since there doesn’t appear to be any evidence for it being harmful in 100mg doses.. Actually if you think about it, even consuming a lot of these hormetics in food form is already a result of them being concentrated in some way: for example cacao powder or dark chocolate versus cocoa beans, red wine versus red grapes etc.. So maybe the answer is to just keep the dose of any ‘extract’ capsules relatively low so that you are not consuming too much of a concentrated, isolated dose that the body may find problematic to deal with in one hit. I have a suspicion that even for example resveratrol capsules, if you went much over 100mg/ day that may tip the balance into it having potentially harmful effects. But unfortunately this can only be pure speculation at the moment!

      Similarly with green tea: I already drink about 5 cups a day of ‘Pukka supreme matcha tea’ (actually only contains 2% matcha powder though), and upon reflection that is probably about as much of the green tea catechins as one needs: the GTE capsule on top of that does feel like overkill now in hindsight.. But it is so easy to fall into the trap of ‘more is better’ with both nutrition and training if you are dedicated to this stuff! It is good to take a good hard look at what you are doing once in a while, so thanks for initiating that! One final thought though, I also came across a recent study that says that if you drink green tea for a few months before taking GTE capsules (as I did) then it ‘acclimatises’ your liver to the effect of the catechins so that when you start the GTE capsules it won’t harm your liver. It does seem to ring true in my case since I have none of the symptoms of liver damage (jaundice, dark urine, nausea), but again taking the bigger picture it now seems unwise to me to be taking such large does of isolated green tea catechins in capsule form on top of my 5 cups of green tea a day: https://www.sciencedaily.com/releases/2015/02/150204112008.htm

      Thanks again for challenging our beliefs – and not being afraid to change your mind when new evidence comes in!

eah says March 27, 2017

Hello Dennis, I wanted to bring this video to your attention:

Dairy Estrogen and Male Fertility


It is claimed that also eggs are a source of such feminizing chemicals.

    Nick says March 28, 2017

    Kinda scary stuff there, if true.

      bigmyc says March 29, 2017

      It is VERY interesting, and if you can read between the incomplete lines like I believe that I have done, the final line of rhetoric in this video says it all;….

      Lowering the cholesterol has no effect on sperm improvement. Boom.
      So, what ShOULD this tell us? Perhaps that cholesterol isn’t the problem with sperm? ..just like it isn’t the problem in heart disease and other ischemic events….that it certainly isn’t the problem in Alzheimer’s and other nuero-degenerative maladies….as is not likely to be implicated in the cause of obesity. More ever, it’s quite obviously that cholesterol is a SYMPTOM of a larger problem which associates with cholesterol but is caused by something else that is amiss.

      The effects of dietary and environmental estrogen can be mitigated and basically denatured by aromatase inhibitors. These substances are also found in “healthier” diets and these also include, surprise, surprise, plenty of “clean” meat and eggs.

      As a matter of fact, there are plenty of instances where vegan and vegetarian diets rendered those partaking in them deficient in vital elements such as B-12, saturated fats and other elemental components of physiological restructuring. I fail to see the sensible correlation between saturated fat and defective reproductive functions. Saturated fat has been a staple throughout the evolution of mankind and while I can’t say much concerning the “safety” of CAFO raised meat products, I can say that I avoid them whenever possible. Those men with the comprised sperm most probably just simply have compromised lifestyles altogether, including the consumption of “tainted” industrially produced meat and eggs.

      These were very broad findings indeed.

        bigmyc says March 29, 2017

        And btw, I didn’t even get into the fact that cholesterol is elemental for the production of sperm.

        Bad science….smh. (Shaking my head)

Nick says March 27, 2017

I started taking it on your advice, and now I’ll stop. I subject my poor liver to enough hardship already.

bigmyc says March 29, 2017

Here’s a very relevant study;

This commentary is quite revealing;
“It appears that EGCG can modulate its own bioavailability and that dietary treatment may reduce the toxic potential of acute high oral doses of EGCG,” said lead researcher Sarah Forester, assistant professor of chemistry, California State University, Bakersfield, a former Penn State postdoctoral fellow.

“These data may partly explain the observed variation in liver toxicity response to dietary supplements containing green tea.”

In another quote; “These data may partly explain the observed variation in liver toxicity response to dietary supplements containing green tea.”

Some people drink surprisingly large volumes of green tea, according to Lambert, as much as 10-20 cups a day, but liver toxicity has never been reported in that context.”

This sounds a lot like how we incorporate vitamin D. People who get plenty of sunlight can handle plenty more sunlight and I believe that would include intense acute further exposure.

Interesting. Of course, like the study suggests, perhaps the most advisable way would be to simply sip green tea.

Nick says April 1, 2017

Well, I got me some Matcha green tea. And … it’s pretty awful. It’s just…too bland, like sipping a hot cardboard infusion or something.

I may have to brew it, chill it, and chug it cool or something, because I can’t see myself regularly sipping this stuff.

    Nick says April 17, 2017

    What I now do is brew up a small cup of black tea and drop a Matcha tea bag into it about half-way done. IOW, make a combined black & green tea. I let it cool, add lemon juice and mineral water and chug it down.

    Is there any reason why I shouldn’t do this?

      P. D. Mangan says April 17, 2017

      Nick: No, can’t think of one. Some people have gotten fluorosis of the bones from drinking either very large quantities of tea – like a gallon a day or something – or drinking “brick tea” in Tibet. Obviously neither of those applies to you (I think? I hope? You don’t live in Tibet do you?)

        Nick says April 17, 2017

        Ha, no, but thanks for your concern. I can’t see myself going beyond a cup of green & black tea a day in any case.

Bill says April 17, 2017

I’ve never been a green tea extract taker. But I have always drunk lots of tea.. This well written article sums up the benefits.

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