13 replies to this topic

[spacey]

The polyphenols present in green tea plants or herbs could pose health risks to humans if extracted and packaged in highly concentrated doses, says a new University of Toronto study published in the current issue of Free Radical Biology and Medicine.

In small mammals, green and black tea phenolics -- a class of chemical compounds found in plants that include polyphenols -- have been proven to contain antioxidants that help reduce the risk of cancer and cardiovascular disease. Findings such as these have helped to make these teas popular choices among health-conscious tea drinkers around the world.

Working with a team of graduate students, Professor Peter O'Brien of the Leslie Dan Faculty of Pharmacy injected low and concentrated doses of polyphenols into mice. At low doses, "good" polyphenols protected the liver or isolated liver cells against oxygen radicals, while "bad" polyphenols caused liver toxicity at high concentrations.

"The low concentration is roughly equivalent to what people consume when they drink green or black tea," O'Brien says. "But the health benefits are not clear as only a small amount of the polyphenols in the teas seems to get absorbed across the intestine. We won't know how much is absorbed or metabolized without running large clinical trials involving humans."

O'Brien has no plans to stop drinking green or black tea anytime soon, but cautions those who might want to exploit the antioxidant and health promoting properties of tea polyphenols against consuming concentrated doses in pill form as this could create more health problems than it might fix.

"New drugs are subjected to exhaustive clinical trials," he says. "Our findings demonstrate that there simply isn't enough known at this time to substantiate green tea's health-promoting properties if taken in high concentrations."

[sUper GeNius]

That's a bugger. According to this link, a cup of green tea has about 100mg of polyphenols. Anyone think drinking 5 to 1 glasses of green tea is excessive?


http://www.mayoclini...tient-green_tea

[Gerald W. Gaston]

That's a bugger. According to this link, a cup of green tea has about 100mg of polyphenols. Anyone think drinking 5 to 1 glasses of green tea is excessive?


http://www.mayoclini...tient-green_tea

Th tea I drink states it has 300mg polyphenols per serving. I only drink 1-2 cups.

But the article is vague. Which "bad" polyphenols, and what is considered a "high concentration"? This similar article from 2007:

http://www.newscient...quantities.html

At least the lead author in that one states: "...that up to 10 small cups of green tea a day is fine. Problems are likely in people who take supplements, which can contain up to 50 times as much polyphenol as a single cup of tea."

[niner]

The Medical News Today article seems a bit alarmist, not to mention data-free. Here is an excerpt from a different paper on dietary polyphenols that is the topic of the link that frankbuzin posted. It seems to be the most pertinent info for humans taking green tea extracts.

http://pubs.acs.org/.../tx7000515.html

Despite several human studies that showed no toxicity of tea polyphenol preparations and that the major adverse effects associated with consumption of high doses of tea preparations are due to gastrointestinal irritation, there have been a number of recent case reports of hepatotoxicity related to the consumption of high doses of tea-based dietary supplements (10-29 mg/kg/day po) (18). In nearly all cases (eight out of nine), patients presented with elevated serum alanine aminotransferase (ALT) and bilirubin levels. In two of nine cases, periportal and portal inflammation were observed. All cases resolved following cessation of supplement consumption. A causative role for the green tea preparations is suggested by the fact that reinjury was observed following rechallenge with the same preparations. The authors of these reports, however, could not conclusively rule out the involvement of potentially hepatotoxic pharmaceutical agents such as acetaminophen or other dietary supplements. One intriguing possibility is that susceptible individuals have a polymorphism in a key biotransformation pathway for the tea polyphenols, such as low activity COMT, which increases exposure to the unmetabolized parent compound. Such possibilities need to be further explored.

Since I'm taking 9.5 mg/kg/day at the moment, this does at least get my attention. Maybe I'll be sure to take them on a full stomach. I could cut back, but I like the psychological side effects of increased motivation. (I can quit any time I want! I just don't want to...) How would you know if you had a weak COMT?

[Forever21]

Is this EGCg? How much is too much?

I'm taking EGCG MAX 700mg (AOR) 3 times a day.

[luminous]

Luckily, green tea also cures liver damage. At least it did four years ago...

Green tea extract fights liver damage in mice
http://www.nutraingr...een-tea-extract

Green tea polyphenols reduced the severity of liver injury in a new study on mice. The researchers say the ingredient could be a useful supplement in the treatment of liver disease.

[luminous]

Here's a fairly recent study stating that green tea is good for fatty liver.

Green tea shows benefits against fatty liver
http://www.nutraingr...gcg-fatty-liver


I'm just mad because I just ordered some highly-concentrated EGCG tablets. Appparently, EGCG is good for the liver at lower doses, bad for the liver at higher doses. Where is the cutoff, I wonder? I was happily drinking a couple of cups of green tea daily until I found out about the high fluoride content in tea. So then I found and ordered the fluoride-free EGCG supplements online, figuring I'd solved the problem. Now I find out that a high concentration of green tea polyphenols could cause liver damage. Sometimes it's hard to find the right balance.

Edited by luminous, 24 June 2008 - 05:05 AM.

[sUper GeNius]

Here's a fairly recent study stating that green tea is good for fatty liver.

Green tea shows benefits against fatty liver
http://www.nutraingr...gcg-fatty-liver


I'm just mad because I just ordered some highly-concentrated EGCG tablets. Appparently, EGCG is good for the liver at lower doses, bad for the liver at higher doses. Where is the cutoff, I wonder? I was happily drinking a couple of cups of green tea daily until I found out about the high fluoride content in tea. So then I found and ordered the fluoride-free EGCG supplements online, figuring I'd solved the problem. Now I find out that a high concentration of green tea polyphenols could cause liver damage. Sometimes it's hard to find the right balance.

Just bite the tablets in half.

Seriously though, you can use a tablet splitter. Can be bought very cheaply in any pharmacy.

Edited by FuLL meMbeR, 24 June 2008 - 06:01 AM.

[kismet]

I'm just mad because I just ordered some highly-concentrated EGCG tablets. Appparently, EGCG is good for the liver at lower doses, bad for the liver at higher doses. Where is the cutoff, I wonder? I was happily drinking a couple of cups of green tea daily until I found out about the high fluoride content in tea. So then I found and ordered the fluoride-free EGCG supplements online, figuring I'd solved the problem. Now I find out that a high concentration of green tea polyphenols could cause liver damage. Sometimes it's hard to find the right balance.

That article sounds like a rehash of older studies, I cannot find any new research.
So far we established that 10-29 mg/kg/day can cause liver and kidney problems.
One intriguing possibility is that susceptible individuals have a polymorphism in a key biotransformation pathway for the tea polyphenols, such as low activity COMT, which increases exposure to the unmetabolized parent compound. [1]

Fluoride content has been discussed, I don't think it's much of a problem with high quality green/white tea.
http://www.imminst.o...mp;hl=green tea

[1] Possible Controversy over Dietary Polyphenols: Benefits vs Risks. Received February 12, 2007. Department of Chemical Biology, Ernest Mario School of Pharmacy, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854. Full: http://pubs.acs.org/...t...)<IN>(CDN))

[Athanasios]

Here is a study that shows why the toxicity will occur, unless this is some new mechanism than the other times around when we covered this issue:
http://clincancerres...t/full/9/9/3312

We conclude that p.o. administration of EGCG or Polyphenon E at a daily dose of 800 mg (based on the EGCG content) for 4 weeks is safe and well tolerated in healthy human subjects. Repeated green tea polyphenol administration at a high daily bolus dose (800 mg once daily) results in a >60% increase in the systemic exposure of EGCG, possibly because of inhibition of presystemic elimination of this catechin. Repeated administration of EGCG and Polyphenon E at a daily dose equivalent to the EGCG content in 16 Japanese-style cups of green tea for 4 weeks did not provide protection against UV-induced erythema.

also note:

The 400-mg twice daily regimen apparently did not result in tea catechin concentrations that would exert a significant inhibitory effect. The mechanism(s) responsible for the observed increase in the AUC of free EGCG after chronic treatment of EGCG/Polyphenon E at a high daily bolus dose remain(s) to be studied. Inhibitions in nonenzymatic degradation, intestinal flora metabolism, methylation, and/or intestinal efflux of EGCG are plausible contributing factors.

And here is the review in which the remarks from Chang are derived:
http://pubs.acs.org/.../tx7000515.html
Check out the mg/kg

Despite several human studies that showed no toxicity of tea polyphenol preparations and that the major adverse effects associated with consumption of high doses of tea preparations are due to gastrointestinal irritation, there have been a number of recent case reports of hepatotoxicity related to the consumption of high doses of tea-based dietary supplements (10-29 mg/kg/day po)

So the end result seems to be to take less than 800mg/day worth of EGCG. I would also consider splitting the dosage if taking 600mg worth or higher in a day.
This is what I take from it but I am not a doctor.

Edited by cnorwood, 13 April 2010 - 06:01 PM.

[krillin]

I take two Source Naturals tablets for tree-fitty mg EGCG.

[luminous]

So the end result seems to be to take less than 800mg/day worth of EGCG (note: not just tea supplement). I would also consider splitting the dosage if taking 600mg worth or higher in a day.
This is what I take from it but I am not a doctor.

cnorwood, thank you so much for the well-sourced information concerning the safe dosage window. Thanks, too, for your clarity regarding EGCG content vs. vague references to excessive "polyphenols" in most of the reports I've found on the internet about the recent study. Pro-Health's Green Tea Mega EGCG is fluoride free and caffeine free and contains 290mg of EGCG per capsule. I feel quite safe taking two of these a day...possibly three.

Edited by luminous, 25 June 2008 - 04:05 AM.

[niner]

Is this EGCg? How much is too much?

I'm taking EGCG MAX 700mg (AOR) 3 times a day.

This is a green tea extract. It contains 700mg of extract, of which 315mg is EGCG. AOR says that a "serving size" is one capsule. On their website, they don't specify a daily dose, but 3 a day is a lot. The safety study that cnorwood posted didn't find any problems with 800mg of EGCG per day in a small number of healthy subjects, but collected from a very large number of users, a few people were found that had problems with as little as 10mg/kg of extract. (From the wording in the article, I conclude that they mean extract and not EGCG here.) So if you are one of those rare individuals, and you weigh 70kg or less, then only one of these pills could be enough to cause a problem. I use a different green tea extract product, but I take only 600mg/day, while you're currently taking 2100mg of extract.

[Forever21]

Is this EGCg? How much is too much?

I'm taking EGCG MAX 700mg (AOR) 3 times a day.

This is a green tea extract. It contains 700mg of extract, of which 315mg is EGCG. AOR says that a "serving size" is one capsule. On their website, they don't specify a daily dose, but 3 a day is a lot. The safety study that cnorwood posted didn't find any problems with 800mg of EGCG per day in a small number of healthy subjects, but collected from a very large number of users, a few people were found that had problems with as little as 10mg/kg of extract. (From the wording in the article, I conclude that they mean extract and not EGCG here.) So if you are one of those rare individuals, and you weigh 70kg or less, then only one of these pills could be enough to cause a problem. I use a different green tea extract product, but I take only 600mg/day, while you're currently taking 2100mg of extract.

Not anymore.