If You are Taking Green Tea Extract Supplements, STOP: They Could Be Damaging Your Liver.

Liquid green tea also requires a rethink.

Green tea (Camellia sinensis) has come to be viewed as an eminently healthy beverage, rich in antioxidants and backed by a mass of epidemiological studies associating it with lower risk of various diseases. Green tea is claimed to possess cardio-protective, anti-cancer, anti-diabetic, antibacterial and even fat-burning effects.

Green tea's purported benefits are largely attributed to a group of bioactive phytochemicals known as catechins, of which the most relevant to today’s discussion is epigallocatechin gallate (EGCG).

As a result of all the buzz, green tea extracts containing concentrated amounts of catechins have been an easy sell. Green tea extract is sold as a standalone product, mixed in with other nutrients in “wellbeing” supplements, and has featured in countless fat loss formulas.

Which is a pity, because these supplements possess a dark side that many people are completely unaware of.

Destroying Your Liver the ‘Healthy’ Way

In animal studies, oral or injectable administration of a large dose of EGCG results in acute liver injury and even death. Repeated EGCG injection (55 or 75 mg/kg/day, for 5 days) to mice induces liver toxicity and suppression of important liver antioxidant enzymes (rather ironic for a substance widely promoted for its antioxidant effects).

Researchers have also found female mice are more sensitive than males to EGCG's toxic effects - a finding that parallels what has been observed in humans.

You wouldn't know it from the glowing health press and supplement blurbs, but green tea extracts have amassed a disturbing volume of human case reports in the medical literature.

If you jump on Pubmed and type in something like "green tea liver damage", you'll probably be shocked by the subsequent volume of citations. A recent review by the United States Pharmacopeia (USP) states:

"Animal and human data indicate that repeated oral administration of bolus doses of [Green Tea Extract] during fasting significantly increases bioavailability of catechins, specifically EGCG, possibly involving saturation of first-pass elimination mechanisms."

What this means is that taking green tea extracts on an empty stomach greatly increases the body's absorption of catechins - and hence may further increase the risk of toxicity.

The term "first-pass" refers to a substance travelling through the liver after being ingested. Toxic substances ingested orally have to first be metabolized by the liver before entering the circulation and being distributed around the body. Those who have researched anabolic drugs will be familiar with this term, and know this is why oral anabolic steroids are generally far more liver toxic than their injectable counterparts, which only pass through the liver for excretion after being metabolized.

The researchers are saying that green tea extracts may be overwhelming the liver’s “first-pass” machinery.

"Toxicological studies show a hepatocellular pattern of liver injury," continue the researchers. "Published adverse event case reports associate hepatotoxicity with EGCG intake amounts from 140 mg to ∼1000 mg/day and substantial inter-individual variability in susceptibility, possibly due to genetic factors."

"Based on these findings, USP included a cautionary labeling requirement in its Powdered Decaffeinated Green Tea Extract monograph that reads as follows: 'Do not take on an empty stomach. Take with food. Do not use if you have a liver problem and discontinue use and consult a healthcare practitioner if you develop symptoms of liver trouble, such as abdominal pain, dark urine, or jaundice (yellowing of the skin or eyes).'” (Bold emphasis added).

There have been warnings about green tea extracts (GTE) from controlled clinical research - but those warnings have gone largely unnoticed by the mainstream and even alternative health press.

The Minnesota Green Tea Trial (MGTT) in postmenopausal women was a randomized, placebo-controlled, double-blind trial investigating the effects of daily GTE consumption for 12 months. The objective was to observe the effects of GTE on biomarkers of breast cancer risk.

Women in the GTE group experienced a worrying 7-fold risk of developing liver abnormalities when compared to the placebo group; 5.1 % of the GTE subjects showed moderate or severe abnormalities in liver function tests. That GTE was the causative factor was confirmed when some of the subjects who developed evidence of liver injury improved after GTE had been stopped, only for it to reappear after they again took GTE.

The Case Reports are Disturbing

There is a large volume of case reports describing liver toxicity and failure after ingestion of GTE supplements. I'll give a few examples here to emphasize how GTE can, without warning, cause unsuspecting users a world of pain.

A 27 year old man developed fatigue and jaundice 4 to 5 weeks after starting the heavily-pimped product Hydroxycut (9 tablets per day) for weight loss. Laboratory tests showed marked elevations in bilirubin and aminotransferase levels. He was hospitalized. Liver tests worsened for a day and then rapidly improved, however his bilirubin and ALT had still not reached normal values at nine weeks.

A 41 year old Hispanic woman in general good health developed fatigue, nausea and weight loss followed by jaundice 3 to 4 weeks after starting Green Tea Fat Burner, a commercial weight loss product labelled as having 20 ingredients, including green tea extract, caffeine, Asian ginseng, beeswax, bilberry, blueberry, eleuthero, elderberry, Yerba mate, pomegranate and Schisandra chinensis. The estimated dose was 800 mg daily for 3 to 4 weeks.

On presentation, she was jaundiced and bilirubin and alkaline phosphatase were markedly elevated, while ALT and AST were in alarming 2,000+ territory. She was initially followed as an outpatient, but worsening symptoms and liver tests saw her hospitalized. An ultrasound and CT scan of the abdomen showed liver enlargement, but no evidence of billiary obstruction. Liver biopsy showed severe acute hepatitis but no fibrosis. She improved slowly. Jaundice persisted for more than a month. At 6 months, liver tests were normal except for mild alkaline phosphatase elevations.

In 2018, the BBC reported on the case of Jim McCants, who began taking GTE at 50 in an effort "to get healthy in middle age." Instead of rejuvenation, he sustained liver injury - and the consequences went far beyond elevated enzymes and a bout of jaundice.

After being hospitalized and subjected to a series of blood tests, one of his doctors delivered the news no-one wants to hear: "[Y]ou need a liver transplant. This has to happen fast. You have days - you don't have a week."

The liver transplant saved Jim's life. But when the BBC spoke to him four years later, he still suffered chronic abdominal pain and serious health problems including kidney disease that may require dialysis and a transplant in the future.

Jim was pursuing a lawsuit against popular American supplement outlet Vitacost, which sold the green tea supplement he took. "I'm hoping that they make the decision to put a very strong warning label on the product, on the website, let people know before they buy it," he said.

Vitacost did not want to comment on the legal case, but simply issued the following rhetoric to the BBC: "We take the safety of our Vitacost brand supplements very seriously and stand behind the quality of our products."

Jim eventually lost the case, after Vitacost’s liar for hire lawyer portrayed him as a self-medicating supplement junkie taking multiple products (the kind of customer that has helped Vitacost attain a $274 million market capitalization), insisting there was no definitive link between Vitacost’s green tea extract and McCants’ 2014 liver failure.

The court decision seems to have emboldened Vitacost to keep ignoring the product’s risks. A visit to the product page for Vitacost Green Tea Extract claims - in bold type - that it “Provides powerful antioxidant protection, guarding healthy cells from free radical damage.” The page makes no mention of liver issues. It simply contains the same generic warning featured for all other supplements stating pregnant or lactating women, diabetics, hypoglycemics, people with “known” medical issues and those taking drugs “should consult with a licensed physician and/or pharmacist prior to taking dietary supplements.”

What About Drinking Green Tea?

"If you are drinking modest amounts of green tea you're very safe," claims Professor Herbert Bonkovsky, director of liver services at Wake Forest University School of Medicine in North Carolina, who has been tracking injuries linked to green tea supplements for nearly 20 years. "The greater risk comes in people who are taking these more concentrated extracts."

Indeed, most of the case reports involve GTE supplements. There is little clinical evidence available on the topic of drinking green tea, and epidemiological studies have claimed a reduced risk of liver cancer among green tea drinkers. Epidemiological evidence, however, has serious issues, including a reliance on memory recall by participants and the unavoidable presence of confounding factors. For example, it's fair to say green tea drinkers have a tendency towards health consciousness, and are likely to engage in other healthy lifestyle factors that may mask a relationship between green tea and liver damage in a highly imprecise endeavour like epidemiology.

Furthermore, much of the epidemiological research is conducted in countries like China and Japan, and may bear little relevance to Westerners because Asians display a lower prevalence of genotypes believed to place people at risk of green tea liver toxicity (more on this in a moment).

Despite the epidemiology and a perception that traditionally brewed green tea is safe, there does exist evidence to show the liquid variety can also pose risks.

A 2015 case report from the UK discussed an otherwise healthy 16-year-old girl presenting with nausea, generalised arthralgia and abdominal pains. She was initially thought to have a urinary tract infection for which she was prescribed amoxicillin. Only two doses were taken before she presented to the emergency department with worsening symptoms and jaundice. All the usual risk factors (alcohol, OTC medications such as paracetamol, illicit drug use, recent travel, blood transfusions, pregnancy, family history) were absent.

On further questioning, the girl admitted to ordering Chinese green tea over the internet, and had been consuming over three cups a day during the preceding three months. When asked why, she explained that she had been told it had weight-loss properties.

On cessation of the green tea and treatment with intravenous fluids and N-acetylcysteine, her hepatitis completely resolved and she was discharged from hospital after a short admission.

The patient was followed up two months after discharge in an outpatient hepatology clinic. She had normal liver function results and had not consumed any further green tea. With other causes of acute hepatitis excluded, and the complete clinical and biochemical resolution observed, green tea was deemed the causative agent.

Italian researchers reported on a 42-year-old woman who suffered sudden onset of jaundice, without fever or abdominal pain. Laboratory analyses revealed highly elevated liver enzymes. A liver biopsy confirmed liver damage.

A detailed review of her clinical history revealed she had been drinking Japanese “matcha” green tea (a micronized water-soluble powder) every other day for ten days. The patient had also been taking for several years irbesartan 150 mg/day for hypertension and a combination estrogenic oral contraceptive.

After three weeks of persistent liver insufficiency and jaundice, prednisone therapy was started. After one month of treatment, her liver enzymes had evinced marked reductions. However, ten days following steroid withdrawal, liver function tests worsened again, so prednisone therapy was resumed. Complete resolution, said the researchers, was attained only after a prolonged course of the immunosuppressive therapy.

Upon investigating the possibility of genetic susceptibility, the researchers found the patient carried genetic variants that could affect phase I and phase II drug metabolism and transport.

While there is research to associate irbesartan and oral contraceptives with the onset of autoimmune hepatic injury, both drugs were well tolerated by the patient for several years. Whether green tea consumption was the sole cause or constituted the "tipping point" at which her liver became overwhelmed from the combination of substances is uncertain.

In an ongoing study of drug-induced liver injury in the US, green tea was judged to be the most likely cause in 40 cases, making it the major single cause of herbal supplement-related liver injury and the sixth most common among all causes.

Eight percent of the green tea-related events were either fatal or required liver transplantation.

In terms of ethnicity, Latino/Hispanic folks were over-represented in green tea-related liver adverse events compared to liver events from other causes.

Green tea was used as an extract in tablet or capsule form in all products except two, one of which was provided as a powder to make tea and the other as a liquid spray. The powdered product was Herbalife Herbal Tea Concentrate, the usage instructions for which recommend a half-teaspoon of concentrate mixed with 6 to 8 fl. oz. of hot or cold water per serving.

Green tea was usually taken for weight loss and most commonly as part of a multi-ingredient product without green tea in its name. The average daily and total accumulated doses were difficult to estimate as most product labels did not provide concentrations of green tea extract or catechins. Nine subjects were taking two green tea-containing supplements concurrently. Chemical analysis indicated catechins and ECGC were present in most products.

Many of the product names will sound familiar to those who frequent supplement forums, and included SLIMQUICK, Hydroxycut, Animal Cuts, Bodyform High Octane, Dexatrim Max, Energy Fizz Sticks, Megamen Powered Ripped and Up Your Gas: Energy Booster.

Give this junk a miss - there are better ways to lose weight that don’t involve hammering your liver.

A "striking" finding in the analysis was a close association of green tea-related liver injury and the HLA allele B*35:01. This allele is carried by 5% to 15% of U.S. populations, rates being lowest in Asian Americans, intermediate in European and African Americans and modestly higher in Hispanics.

Which shows that just because the Okinawans or Japanese or some other group promoted by the Blue Zones crowd allegedly consume certain foods or drinks, doesn't automatically mean you should too.

While carried by 5-15% of Americans, this allele was found in 72% of patients with green tea-associated liver injury and more than 90% of those in whom the injury was judged as highly likely or definite.

Conclusion

I'm not a doctor and therefore anything I say here does not constitute medical advice. That said, I would implore readers to stay away from green tea extracts. There are plenty of other beneficial supplements that help boost your daily intake of antioxidants without putting you at risk of an emergency ward visit for liver toxicity and even failure.

As for weight loss, exercise and calorie restriction remain the cornerstone of any safe and effective fat loss strategy. If you don’t like eating less, then do what I do and remain highly active.

Females, people of Latino/Hispanic ethnicity, those taking other medications, and people using multi-component formulas (a common feature of fat loss formulas containing GTE) seem to be at heightened risk.

Research suggests certain genotypes increase the risk of liver injury in response to GTE, but none of these products come with a genetic testing kit to determine whether you are at heightened risk.

While reports of liver injury from liquid green tea are much rarer, they exist, indicating that at least for some people, this “healthy drink” is not a benign beverage. Two of the cases discussed above involved powdered products designed to be dissolved in water, a mode of delivery that may increase the concentration of catechins like EGCG.

The authors of a recent review of adverse event data suggested "concentrated, catechin-rich green tea preparations resulted in hepatic AEs in a dose-dependent manner when ingested in large bolus doses, but not when consumed as brewed tea or extracts in beverages or as part of food … A safe intake level of 338 mg EGCG/day for adults was derived from toxicological and human safety data for tea preparations ingested as a solid bolus dose."

I'd regard that passage with caution. As discussed, green tea as a beverage has shown the potential to cause adverse liver events. Researchers have also reported cases arising from apparent consumption of less than 338 mg EGCG daily. Furthermore, recommendations to keep EGCG below a certain threshold are confounded by the fact that many products don't state their EGCG content.

Again, I'd give green tea extracts a very wide berth, and if you have any sign of liver issues or fall into any of the risk groups, I'd also be seriously reconsidering liquid green tea consumption.