Health Canada will strengthen warnings on labels by
including the language: “Rare, unpredictable cases of liver injury
associated with green tea extract-containing products have been reported
(in Canada and internationally).”
Related: Is It Dangerous to Drink Too Much Green Tea?
A federal review in Canada
concluded that while the majority of people who take green-tea extract
“in any form, do so without harm,” they also found that “there may be a
link between the use of green tea extract and a risk of rare and
unpredictable liver injury.”
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The warnings are nothing new—including in the U.S. In 2014, The American College of Gastroenterology released guidelines on drugs and herbal supplements that can cause liver injury. Topping the list of herbals? You guessed it: green-tea extract. Some pills, they note in the press release,
can contain more than 700 milligrams (mg) of catechins (the active
compound in green tea), whereas a cup of green tea contains 50 to 150
mg, and people tend to take these pills multiple times a day.
"In animal studies, when some strains of mice are given high doses of
EGCG (the active catechin in green tea), they develop acute liver
injury that looks like Tylenol toxicity," explains Herbert Lloyd
Bonkovsky, M.D., gastroenterology professor at Wake Forest Baptist
Health. He notes that some people—because of factors like genetics—may
be more prone to liver damage than others. "Fasting also increases the
absorption of catechins, meaning there may be a higher risk of injury
for people who are trying to lose weight," he says.
Bonkovsky also notes that while drinking green tea is almost always
safe, there have been some reports of people developing liver injury
after consuming large amounts, like eight or 10 cups a day.
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Another study in 2017 in the journal Hepatology also found that anabolic steroids and green-tea extract were two of the most common supplements to cause liver damage.
