GTE intake significantly increased both ALT and AST during the treatment period from baseline levels. On the contrary, such changes of AKP and total bilirubin were not statistically significant between GTE and placebo arms Table 2.

Change of serum liver functional tests during the intervention period from baseline in all participants, the Minnesota Green Tea Trial, to a Two-sided P values were derived from generalized linear mixed models comparing the changes of liver functional tests during the intervention period from baseline among women in the GTE group to the corresponding changes in the placebo group after adjustments for age, level of education, body mass index, and smoking status.

Among women with normal baseline ALT in the GTE arm, 44 8. Furthermore, 17 3. We did not detect any statistically significant difference in age, race, education, BMI, use of alcohol, history of smoking, use of aspirin, other NSAIDs or acetaminophen, and use of statin. The baseline mean levels of total cholesterol, total triglyceride, AKP, and total bilirubin were comparable between these two groups Supplementary Table S3.

Although all baseline ALT were within normal range, subjects whose ALT increased above 1. OR of developing abnormal liver functional tests for women assigned to the GTE versus placebo group during the month treatment period, the Minnesota Green Tea Trial, to a OR were derived from unconditional logistic regression models that also included age, BMI, smoking status, and level of education.

b Abnormal hepatic aminotransferases was defined as having at least one elevation above ULN during the monthly LFTs after randomization. c OR was derived from exact logistic regression model, and upper confidence interval was not estimated. Similar to ALT, AST level increased in 66 AST was highly correlated with ALT.

GTE intake had no effect on AKP and total bilirubin Table 3. When the four measures for drug-induced liver function abnormalities were considered together, 26 participants in the GTE arm and four in the placebo arm had one or more moderate liver enzyme elevations, yielding an OR of 7.

The effect of GTE intake on ALT and AST elevation was stronger in obese women, but less in weekly alcohol drinkers Table 4. Change of serum ALT and AST during the intervention period from baseline in subgroups stratified by selected baseline characteristics, the Minnesota Green Tea Trial, to a Two-sided P values were derived from generalized linear mixed models comparing the changes of liver enzyme ALT or AST during the intervention period from baseline of women in the GTE group to the corresponding changes in the placebo group after adjustments for age, BMI, smoking status, and level of education.

b Two-sided P values were derived from the same model assessing the interaction between the intervention GTE or placebo and the stratifying variables on the liver enzyme ALT or AST with the same adjustments. c Two-sided P values were derived from the same model comparing the differences in changes of liver enzyme ALT or AST from baseline among different levels of stratifying variables within the GTE or placebo group.

Overall, 17 women—all in the GTE arm—had ALT above 2. This analysis demonstrates that sustained consumption of a high daily dose of GTE as a dietary supplement approximately 1, mg total tea catechins, mg EGCG may relate with mild to severe liver enzyme elevation in a small percentage 5.

Compared with women in the placebo group, participants randomized to receive GTE capsules were approximately seven times more likely to develop mild or more severe i. The induction period from the initial intake to the manifestation of mild or more severe liver enzyme elevation varied widely among different participants, from a minimum of 2 months to a maximum of 1 year.

Abnormal LFTs induced by GTE were transient; ALT levels returned to below 1. Among women who experienced initial liver enzyme elevation i. The rise-fall pattern of serum liver enzyme levels following the dechallenge—rechallenge cycles of GTE treatment strongly implicates a possible association of this high-dose GTE capsule regimen on liver laboratory abnormalities in a subset of postmenopausal women who are sensitive to GTE.

Green tea-based products are the fifth most commonly consumed dietary supplement in the United States Some brands of green tea supplements contain as much as 1, mg tea catechins in a single tablet.

The public should be aware of the potential liver injury from consumption of high-dose green tea—based products. Our findings are based on a well-designed and carefully implemented randomized, double-blinded, placebo-controlled phase II clinical trial of GTE in a large population of healthy U.

These unequivocal results ruled out possibilities of confounding effects inherent in previous case reports on the liver injury of green tea-based products 11, All study participants had normal baseline liver function panels, had no infection with hepatitis B or C virus or history of liver disease.

Both GTE and placebo capsules were produced by the same GMP-certified facility with high standard of quality control. The contents of both GTE and placebo capsules were well characterized and quantified. In addition, compliance was monitored rigorously Thus, the liver enzyme elevations are easily interpretable and attributable to GTE.

The biological mechanism whereby GTE provokes liver injury is not well-understood. In vitro and in vivo animal experiments support the pro-oxidant property of tea catechins; EGCG facilitates generation of reactive oxygen species ROS , depletion of glutathione, and collapse of the mitochondrial membrane potential of hepatocytes Excess production of ROS may alter intracellular proteins, increase cell membrane permeability, and induce apoptosis It has been demonstrated that glutathione-depleted cells are susceptible to oxidation and further cell damage EGCG-related ROS formation occurs biphasically, that is, at low doses EGCG decreases ROS production whereas at high doses EGCG increases ROS generation and damages the mitochondrial membrane of hepatocytes Obesity and its complications, including dyslipidemia, inflammation, and oxidative stress, are strong metabolic risk factors for fatty liver disease 24, In one longitudinal study in a Mexican population, weight gain increased ALT levels by more than three times The high prevalence of obesity in the United States has led to high incidence of nonalcoholic fatty liver disease and chronic liver disease Green tea—based products are widely used as a dietary supplement for weight loss 28— However, high doses of tea catechins may enhance liver injury, especially for obese individuals along with oxidative stress 9, This study, similar to previous case reports, showed that the use of statins was significantly associated with elevated ALT at baseline.

Among 53 case reports of liver injury associated with intake of GTE or tea-based products, 28 were consuming other medications concurrently 11, Thus, the use of medications or preexisting conditions that require medication may exacerbate GTE-induced liver abnormal tests.

In a small clinical trial involving 11 patients with multiple sclerosis 32 , five of the six patients assigned to receive Polyphenon E a mixed GTE formulation similar to ours at a daily dose of mg EGCG developed abnormal ALT compared to one in five control subjects who had a similarly abnormal ALT.

The major limitation of this study is its generalizability. All study participants were healthy postmenopausal women and virtually all were Caucasian. We do not know if the impact of GTE on liver enzyme elevation would be stronger in women who drink alcohol more frequently e.

general population with high prevalence of obesity and high level of alcohol intake because obesity or heavy alcohol use may exacerbate the adverse effect of GTE on liver health. Moreover, the effects of specific ingredients in commercial green tea supplements on liver enzyme elevation cannot be ascertained from this study.

The MGTT study protocol did not call for further pathological evaluation of women who experienced ALT elevation to the level of severe liver injury.

Future studies are warranted to elucidate the biological mechanisms for GTE on liver injury. This randomized, double-blinded, placebo-controlled phase II clinical trial clearly demonstrates that high-dose of GTE intake for approximately 12 months associated with liver enzyme elevation in a small proportion of healthy postmenopausal women.

The public should be informed about the potential risk of liver injury with a high, sustained dose of GTE as a dietary supplement, especially for those who are obese or have preexisting liver disease.

Butler is an epidemiologist at Genentech, Inc. No potential conflicts of interest were disclosed by the other authors. Acquisition of data provided animals, acquired and managed patients, provided facilities, etc.

Samavat, A. Dostal, C. Torkelson, M. Analysis and interpretation of data e. Yu, R. Wang, L. Butler, T. Kensler, A. Wu, J. Yu, H. Torkelson, C. Yang, L. Wu, M. Kurzer, J.

Administrative, technical, or material support i. The authors would like to acknowledge the study participants, the data collection team, and study administrative staff at the Human Nutrition Research Clinic, Department of Food Science and Nutrition, University of Minnesota; the Oncology Research Department of the Park Nicollet Institute St.

Louis Park, MN , and the Investigational Drug Services pharmacy of the University of Minnesota Medical Center, Fairview.

The Minnesota Green Tea Trial was supported by the U. National Cancer Institute R01 CA; to M. This work was partially supported by the U. National Cancer Institute UM1 CA, to J. Yuan; R35 CA, to T.

Kensler; T32CA, A. Both the National Cancer Institute's Cancer Center Support Grants of the University of Minnesota Masonic Cancer Center P30 CA and the University of Pittsburgh Cancer Institute P30 CA partially supported this work. The costs of publication of this article were defrayed in part by the payment of page charges.

This article must therefore be hereby marked advertisement in accordance with 18 U. Section solely to indicate this fact. Supplemental Table S1 shows the severity grading in Drug Induced Liver Injury from LIVERTOX produced by AIDS CTG.

Supplemental Table S2 shows the baseline mean concentrations of alanine aminotransferase ALT and aspartate aminotransferase AST in all participants and in subgroups stratified by selected characteristics of study participants by treatment status GTE or placebo.

Supplemental Table S4 shows the grading of ALT during the month treatment period by the level of baseline liver function tests and the interaction with treatment assignment GTE or Placebo. Then promote the pill as a cancer-fighting or fat burning supplement.

But here we run into a problem. Such dietary supplements are poorly regulated and the amount of catechins they contain can be far greater than that available from drinking tea. The high doses may indeed help to increase metabolism and result in weight loss but possibly at a high cost.

Doctors feared he may need a liver transplant but luckily his liver, an organ that has regenerative properties, managed to recover. He did, however, have to give up sporting activities and will require regular checkups of his liver function.

Unfortunately this is not an isolated case and such cases are not limited to green tea extracts. Various herbal supplements have been linked with liver damage, some because of undeclared ingredients, such as steroids. These are promoted as bodybuilding supplements and may actually have an effect because of the hidden steroids.

People generally assume that herbal products that are sold are tested for safety and efficacy but this is not the case. Until regulations are tightened the incidence of liver damage from dietary supplements is going to continue to increase.

McGill University Office for Science and Society Separating Sense from Nonsense. Or, if you've started drinking lots of matcha , it might not be a bad idea to check in with your doc since it's a concentrated form of green tea.

As for supplements , you should always play it on the safe side, as even natural ingredients can carry some serious side effects.

Bottom line: Pay attention to what you're putting into your body. Just because it's natural, doesn't mean more is better.

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The public should be aware of the potential liver injury from consumption of high-dose green tea—based products. Our findings are based on a well-designed and carefully implemented randomized, double-blinded, placebo-controlled phase II clinical trial of GTE in a large population of healthy U.

These unequivocal results ruled out possibilities of confounding effects inherent in previous case reports on the liver injury of green tea-based products 11, All study participants had normal baseline liver function panels, had no infection with hepatitis B or C virus or history of liver disease.

Both GTE and placebo capsules were produced by the same GMP-certified facility with high standard of quality control. The contents of both GTE and placebo capsules were well characterized and quantified. In addition, compliance was monitored rigorously Thus, the liver enzyme elevations are easily interpretable and attributable to GTE.

The biological mechanism whereby GTE provokes liver injury is not well-understood. In vitro and in vivo animal experiments support the pro-oxidant property of tea catechins; EGCG facilitates generation of reactive oxygen species ROS , depletion of glutathione, and collapse of the mitochondrial membrane potential of hepatocytes Excess production of ROS may alter intracellular proteins, increase cell membrane permeability, and induce apoptosis It has been demonstrated that glutathione-depleted cells are susceptible to oxidation and further cell damage EGCG-related ROS formation occurs biphasically, that is, at low doses EGCG decreases ROS production whereas at high doses EGCG increases ROS generation and damages the mitochondrial membrane of hepatocytes Obesity and its complications, including dyslipidemia, inflammation, and oxidative stress, are strong metabolic risk factors for fatty liver disease 24, In one longitudinal study in a Mexican population, weight gain increased ALT levels by more than three times The high prevalence of obesity in the United States has led to high incidence of nonalcoholic fatty liver disease and chronic liver disease Green tea—based products are widely used as a dietary supplement for weight loss 28— However, high doses of tea catechins may enhance liver injury, especially for obese individuals along with oxidative stress 9, This study, similar to previous case reports, showed that the use of statins was significantly associated with elevated ALT at baseline.

Among 53 case reports of liver injury associated with intake of GTE or tea-based products, 28 were consuming other medications concurrently 11, Thus, the use of medications or preexisting conditions that require medication may exacerbate GTE-induced liver abnormal tests.

In a small clinical trial involving 11 patients with multiple sclerosis 32 , five of the six patients assigned to receive Polyphenon E a mixed GTE formulation similar to ours at a daily dose of mg EGCG developed abnormal ALT compared to one in five control subjects who had a similarly abnormal ALT.

The major limitation of this study is its generalizability. All study participants were healthy postmenopausal women and virtually all were Caucasian.

We do not know if the impact of GTE on liver enzyme elevation would be stronger in women who drink alcohol more frequently e. general population with high prevalence of obesity and high level of alcohol intake because obesity or heavy alcohol use may exacerbate the adverse effect of GTE on liver health.

Moreover, the effects of specific ingredients in commercial green tea supplements on liver enzyme elevation cannot be ascertained from this study. The MGTT study protocol did not call for further pathological evaluation of women who experienced ALT elevation to the level of severe liver injury. Future studies are warranted to elucidate the biological mechanisms for GTE on liver injury.

This randomized, double-blinded, placebo-controlled phase II clinical trial clearly demonstrates that high-dose of GTE intake for approximately 12 months associated with liver enzyme elevation in a small proportion of healthy postmenopausal women.

The public should be informed about the potential risk of liver injury with a high, sustained dose of GTE as a dietary supplement, especially for those who are obese or have preexisting liver disease. Butler is an epidemiologist at Genentech, Inc.

No potential conflicts of interest were disclosed by the other authors. Acquisition of data provided animals, acquired and managed patients, provided facilities, etc. Samavat, A. Dostal, C. Torkelson, M. Analysis and interpretation of data e. Yu, R. Wang, L.

Butler, T. Kensler, A. Wu, J. Yu, H. Torkelson, C. Yang, L. Wu, M. Kurzer, J. Administrative, technical, or material support i. The authors would like to acknowledge the study participants, the data collection team, and study administrative staff at the Human Nutrition Research Clinic, Department of Food Science and Nutrition, University of Minnesota; the Oncology Research Department of the Park Nicollet Institute St.

Louis Park, MN , and the Investigational Drug Services pharmacy of the University of Minnesota Medical Center, Fairview. The Minnesota Green Tea Trial was supported by the U.

National Cancer Institute R01 CA; to M. This work was partially supported by the U. National Cancer Institute UM1 CA, to J.

Yuan; R35 CA, to T. Kensler; T32CA, A. Both the National Cancer Institute's Cancer Center Support Grants of the University of Minnesota Masonic Cancer Center P30 CA and the University of Pittsburgh Cancer Institute P30 CA partially supported this work.

The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U. Section solely to indicate this fact. Supplemental Table S1 shows the severity grading in Drug Induced Liver Injury from LIVERTOX produced by AIDS CTG.

Supplemental Table S2 shows the baseline mean concentrations of alanine aminotransferase ALT and aspartate aminotransferase AST in all participants and in subgroups stratified by selected characteristics of study participants by treatment status GTE or placebo.

Supplemental Table S4 shows the grading of ALT during the month treatment period by the level of baseline liver function tests and the interaction with treatment assignment GTE or Placebo. Supplemental Table S5 demonstrates the change of serum ALT and AST during the intervention period from baseline in subgroups stratified by selected baseline characteristics.

Sign In or Create an Account. Search Dropdown Menu. header search search input Search input auto suggest. Advanced Search. User Tools Dropdown. Sign In. Toggle Menu Menu About The Journal Editorial Board AACR Journals Subscriptions Permissions and Reprints Articles Online First Issues Meeting Abstracts PreCancer Atlas Collection: From Biology to Cancer Interception Collection: Biology of Susceptibility and Premalignancy Collection: E-Cigarettes Collection: Must-Read Articles Collection: Editors' Picks COVID 'Best 'Of' Collection For Authors Information for Authors Author Services Outstanding Journal Article Award Best of: Author Profiles Submit Alerts News Cancer Hallmarks Webinars.

Skip Nav Destination Close navigation menu Article navigation. Volume 10, Issue Previous Article Next Article. Materials and Methods. Disclosure of Potential Conflicts of Interest. Authors' Contributions. Grant Support. Article Navigation. Research Articles October 01 Effect of Green Tea Supplements on Liver Enzyme Elevation: Results from a Randomized Intervention Study in the United States Zheming Yu ; Zheming Yu.

This Site. Google Scholar. Hamed Samavat ; Hamed Samavat. Paul, Minnesota. Allison M. Dostal ; Allison M. Renwei Wang ; Renwei Wang. Carolyn J. Torkelson ; Carolyn J. Chung S. Yang ; Chung S.

Lesley M. Butler ; Lesley M. Thomas W. Kensler ; Thomas W. Anna H. Wu ; Anna H. Mindy S. Kurzer ; Mindy S. Phone: ; Fax: ; E-mail: yuanj upmc. gov Identifier: NCT Received: May 20 Revision Received: July 06 Accepted: July 28 Online ISSN: Funding Group: Award Group: Funder s : National Cancer Institute.

Award Group: Funder s : National Cancer Institute. Award Group: Funder s : Department of Defense. Award Group: Funder s : University of Minnesota Masonic Cancer Center. Award Group: Funder s : University of Pittsburgh Cancer Institute. Cancer Prev Res Phila 10 10 : — Article history Received:.

Revision Received:. Cite Icon Cite. toolbar search Search Dropdown Menu. toolbar search search input Search input auto suggest. Figure 1. View large Download slide.

Table 1. years of quitting smoking, mean SD of drinks per week, mean SD 3. b The sum of some variables may be less than the total due to missing values. View Large. Table 2. Table 3. Table 4. P int c. COMT, catecheol-O-methyltransferase. All means are from least squares means.

Figure 2. Conception and design: Z. Yu, C. Yang, M. Development of methodology: M. Study supervision: M. Search ADS. Green tea and liver cancer risk: a meta-analysis of prospective cohort studies in Asian populations. Green tea consumption and mortality due to cardiovascular disease, cancer, and all causes in Japan: the Ohsaki study.

Mechanisms of body weight reduction and metabolic syndrome alleviation by tea. Prevention of chronic diseases by tea: possible mechanisms and human relevance. Green tea polyphenol - -epigallocatechingallate triggered hepatotoxicity in mice: responses of major antioxidant enzymes and the Nrf2 rescue pathway.

But soon after his son's graduation, Jim was admitted to hospital with a suspected liver injury. Trying to identify the cause of Jim's liver injury, those treating him ruled out alcohol.

So alcohol was not a big part of my life," Jim says. They also ruled out prescription drugs - he wasn't taking any at the time - and smoking, something he had never done. Watch the BBC Two Horizon programme Vitamin pills: Miracle or Myth?

online UK viewers only. BBC Food: Can a vitamin pill a day keep the doctor away? As part of his mid-life health kick, Jim had started taking a green tea supplement because he had heard it might have cardiac benefits.

These supplements have grown in popularity in recent years, often breathlessly promoted online for their antioxidant benefits, and their supposed ability to aid weight loss and prevent cancer.

He had been taking the green tea supplement for two to three months when he became ill. According to Jim's medical record this is the presumed cause of his liver injury.

After his admission to hospital, Jim went into a "holding pattern", waiting for the results of a series of blood tests to establish the seriousness of his liver injury.

Then, about three weeks after his wife had first noticed he looked ill, one of his liver doctors delivered the news he had been fearing: "She said you need a liver transplant. This has to happen fast. You have days - you don't have a week. It really crystallises what's important in life.

I wasn't there thinking about projects at work. I was thinking of different people that were important to me for different reasons. What is it about green tea supplements that might cause harm at certain doses to some people?

Scientists do not know for certain. Because green tea has been drunk for thousands of years, supplements consisting of its concentrated form are regulated in the US and Europe as foods, not medicines.

That means that specific safety testing has not been required, so the scientific picture of how green tea supplements might affect our health is incomplete. Concern has focused on a potentially toxic ingredient called Epigallocatechingallate or EGCG, the most abundant of the naturally occurring compounds with antioxidant properties in green tea, called catechins.

There are likely to be a number of factors that might make an individual susceptible to harm from EGCG including genetics, and the way supplements are used. There may well be other factors of other drugs, other chemicals, use of alcohol that are also important as modifying factors.

Antioxidants are a group of vitamins and other compounds that for many have taken on miraculous properties, helping to drive the global market for supplements of all kinds, now worth more than £bn per year. Antioxidants ward off "free radicals", molecules produced in our cells as they turn oxygen and food into energy.

Just as oxygen and water corrode iron, too many free radicals can damage our cells. In the s, Prof Denham Harman theorised that free radicals drove the process by which the body ages and could lead to disease.

But some scientists now believe that free radicals at certain levels may be beneficial for human health, and argue that the orthodox view of the last half century that antioxidants are an unalloyed good is outdated.

While millions of people take green tea supplements safely, at least 80 cases of liver injury linked to green tea supplements have been reported around the world, ranging from lassitude and jaundice to cases requiring liver transplants.

A study involving 10 people revealed that applying a cream containing green tea extract to the skin for 60 days resulted in improved skin elasticity Additionally, a study showed that applying green tea extract to the skin reduced skin damage caused by sun exposure Interestingly enough, adding green tea extract to cosmetic products has been shown to benefit the skin by providing a moisturizing effect Antioxidants, like green tea catechins, can reduce cellular damage and delay muscle fatigue 44 , Additionally, 16 sprinters who took green tea extract for 4 weeks demonstrated increased protection against oxidative stress produced by repeated sprint bouts One study found that 14 men who actively engaged in physical activity and consumed green tea extract for 4 weeks increased their running distance by Green tea extract increases antioxidant protection against oxidative damage caused by exercise.

This translates to better exercise performance and recovery. The catechins in green tea, especially EGCG, have been shown to enhance insulin sensitivity and regulate the production of blood sugar, both of which can lower blood sugar levels 49 , A study gave 14 people with no underlying health conditions a sugary substance and either 1.

The group that consumed green tea experienced better blood sugar tolerance after 30 minutes and continued to show better results compared with the placebo group Keep in mind that these studies 51 , 52 were very small and that the participants had no underlying health conditions.

Many people with diabetes, on the other hand, take medications that affect their liver, and many have NAFLD, so they would need to monitor their liver enzymes. An analysis of 17 studies concluded that green tea extract is useful in decreasing fasting blood sugar levels. It can also help lower the hemoglobin A1C value, which is an indicator of blood sugar levels over the past 2—3 months Green tea extract has been shown to increase insulin sensitivity and blood sugar tolerance, all while decreasing hemoglobin A1C and blood sugar levels.

Green tea extract is available in liquid, powder, and capsule forms. A wide selection can be found on Amazon. The liquid extract can be diluted in water, while the powder can be mixed into smoothies. However, it has a strong taste.

The recommended dosage of green tea extract is between — mg per day. This amount can be obtained from 3—5 cups of green tea, or about 1. Some supplements contain only dry green tea leaves, while others contain isolated forms of one or more catechins.

Because supplements are not FDA regulated to ensure safety, purity, or verification of contents, you should only purchase supplements that have been analyzed by an independent lab to verify purity and content.

Both exceeding the recommended dose and taking it on an empty stomach may cause serious liver damage 30 , Green tea extract can be consumed in capsule, liquid, or powder form. The recommended dose is — mg, taken with food.

Thanks to its high antioxidant content, green tea extract has been shown to help improve health and body composition. Many studies have shown that green tea extract can promote weight loss, blood sugar regulation, disease prevention, and exercise recovery.

It can also help keep your skin and liver healthy, reduce blood fat levels, regulate blood pressure, and improve brain health. It can be consumed in capsule, liquid, or powder form. Amounts above this may be toxic. Plus, people with diabetes or those taking certain medications should speak with a healthcare professional before taking any amount of green tea extract.

Whether you want to improve your general health or decrease your risk of disease, green tea extract is an easy way to add health-boosting antioxidants to your diet. Our experts continually monitor the health and wellness space, and we update our articles when new information becomes available.

VIEW ALL HISTORY. EGCG is a plant compound particularly prominent in green tea that's linked to several benefits.

This article reviews EGCG, including its health…. This is a detailed article about green tea and its health benefits. Green tea is high in antioxidants that can improve the function of your body and….

Discover how green tea can help with oily skin, acne, making your skin look younger. Also, learn about its effects regarding melanoma and nonmelanoma…. Many studies show that green tea can help you lose weight. It contains bioactive substances that can make you burn more calories, even at rest. Many companies have started adding green tea to their products, especially those that claim to make your hair healthier.

This article gets to the root…. Phosphatidylcholine is known to boost cognition, but its potential benefits don't stop there. Here's what you should know about this herbal remedy.

Research suggests rhodiola and ashwagandha work well together, but you may want to take them at different times of day. A Quiz for Teens Are You a Workaholic?

How Well Do You Sleep? Health Conditions Discover Plan Connect. Nutrition Evidence Based 10 Benefits of Green Tea Extract. Medically reviewed by Jerlyn Jones, MS MPA RDN LD CLT , Nutrition — By Arlene Semeco, MS, RD and Alyssa Northrop, MPH, RD, LMT — Updated on May 31, How we vet brands and products Healthline only shows you brands and products that we stand behind.

Our team thoroughly researches and evaluates the recommendations we make on our site. To establish that the product manufacturers addressed safety and efficacy standards, we: Evaluate ingredients and composition: Do they have the potential to cause harm? Fact-check all health claims: Do they align with the current body of scientific evidence?

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Was this helpful? High in antioxidants. May promote heart health. Good for the brain. Can help with weight loss. Might benefit liver function. May reduce the risk of cancer.

May be good for the skin. May benefit exercise performance and recovery. May help lower blood sugar. Easy to add to your diet. The bottom line. How we reviewed this article: History. May 31, Written By Arlene Semeco, Alyssa Northrop, MPH, RD, LMT.

Medically Reviewed By Jerlyn Jones, MS MPA RDN LD CLT. May 10, Written By Arlene Semeco, Alyssa Northrop, MPH, RD, LMT. Share this article. Read this next. EGCG Epigallocatechin Gallate : Benefits, Dosage, and Safety.

I was thinking of different people that were important to me for different reasons. What is it about green tea supplements that might cause harm at certain doses to some people?

Scientists do not know for certain. Because green tea has been drunk for thousands of years, supplements consisting of its concentrated form are regulated in the US and Europe as foods, not medicines. That means that specific safety testing has not been required, so the scientific picture of how green tea supplements might affect our health is incomplete.

Concern has focused on a potentially toxic ingredient called Epigallocatechingallate or EGCG, the most abundant of the naturally occurring compounds with antioxidant properties in green tea, called catechins.

There are likely to be a number of factors that might make an individual susceptible to harm from EGCG including genetics, and the way supplements are used. There may well be other factors of other drugs, other chemicals, use of alcohol that are also important as modifying factors.

Antioxidants are a group of vitamins and other compounds that for many have taken on miraculous properties, helping to drive the global market for supplements of all kinds, now worth more than £bn per year. Antioxidants ward off "free radicals", molecules produced in our cells as they turn oxygen and food into energy.

Just as oxygen and water corrode iron, too many free radicals can damage our cells. In the s, Prof Denham Harman theorised that free radicals drove the process by which the body ages and could lead to disease.

But some scientists now believe that free radicals at certain levels may be beneficial for human health, and argue that the orthodox view of the last half century that antioxidants are an unalloyed good is outdated. While millions of people take green tea supplements safely, at least 80 cases of liver injury linked to green tea supplements have been reported around the world, ranging from lassitude and jaundice to cases requiring liver transplants.

Those harmed after taking green tea pills have included teenagers, like year-old Madeline Papineau from Ontario, Canada who developed liver and kidney injury, and an year-old woman diagnosed with toxic acute hepatitis.

A recent investigation by the European Food Safety Authority into the safety of green tea concluded that catechins from green tea drinks are "generally safe", but when taken as supplements catechin doses at or above mg per day "may pose health concerns".

The EFSA could not identify a safe dose on the basis of available data and called for more research to be carried out.

The day after Jim was told he needed a liver transplant, amazingly he was told a suitable liver had been found. The phone call that there was a match gave me hope that there would be something positive on the other side of this for me," he says.

The liver transplant saved Jim's life. But four years later he still has serious health problems including kidney disease that may require dialysis and a transplant in the future. He sees his liver and kidney doctors twice a year, and lives with chronic abdominal pain. And now it's much more sedentary and I struggle with fatigue," he says.

It's a "tremendous blessing", as he puts it, that his managers allow him to work from home. I'm able to just let my manager know I'm going offline, I'll be back.

Jim is pursuing a lawsuit against the American firm Vitacost, which sold the green tea supplement he took. Vitacost did not want to comment on the legal case, but said: "We take the safety of our Vitacost brand supplements very seriously and stand behind the quality of our products.

Four years on, Jim reflects on how his life and that of his family changed after he took a green tea supplement. I expected that I might waste my money, I may take these and they don't do a bit of good.

I can accept that risk," he says. British army officer Naima Houder-Mohammed paid thousands of dollars to the father of the alkaline diet, Robert O Young, for a treatment that she falsely believed would cure her cancer.