Green Tea Extract and EGCG Supplements vs Tea: Evidence and Liver Safety
How brewed green tea differs from green tea extract and EGCG capsules, what trials found for weight, cholesterol and heart health, and what is reported about liver injury.
Content last updated . This page has not been medically reviewed.
What is Green tea extract and EGCG good for?
What the body uses it for, and how strong the evidence is. A normal job in the body is not proof that extra supplements add benefit; each card says which.
Antioxidant activity in the lab
Lab or animal research onlyGreen tea catechins neutralise free radicals in laboratory tests.
Supplements: Lab antioxidant activity does not show that supplements prevent disease or slow ageing.
Cholesterol (total and LDL)
Preliminary or mixedTrials, mostly of extract supplements, found modest drops in total and LDL cholesterol, with no change in HDL or triglycerides.
Supplements: Small effect; few trials; not a substitute for medical cholesterol care.
Body weight
Preliminary or mixedA Cochrane review found small, non-significant weight loss in overweight adults, unlikely to be clinically important.
Supplements: No good evidence of meaningful weight loss.
Blood pressure and heart risk factors
Preliminary or mixedGreen tea lowered LDL and blood pressure in a few trials, but no trial reported heart disease events and results were not stable.
Supplements: Evidence is limited; extract can itself raise blood pressure as a side effect.
Cancer prevention
Not enough evidenceCochrane found inconsistent results and limited evidence that green tea prevents cancer; extract trials reported stomach upset and raised liver enzymes.
Supplements: Insufficient evidence that supplements prevent cancer.
Prescription ointment for genital warts
Clinically supportedThe FDA has approved a specific green tea extract ointment applied to the skin for external genital and perianal warts.
Supplements: Does not apply to oral supplements.
Connected topics
Open a group to see how each topic connects and how strong the evidence is.
Health goals (6)
- Cholesterol BalancePreliminary or mixed
Trials, mostly of extracts, showed modest drops in total and LDL cholesterol with no change in HDL or triglycerides.
- Liver SupportDocumented risk
Despite the common marketing of green tea for 'liver support', extract is linked to liver injury reports, so it is a liver caution rather than a liver aid.
- Weight ManagementPreliminary or mixed
A Cochrane review of trials of at least 12 weeks found small, non-significant weight loss unlikely to matter clinically; NCCIH says any effect is modest.
- Blood Pressure SupportPreliminary or mixed
A Cochrane review found green tea lowered blood pressure in a few trials, but results were not stable. Extract can also raise blood pressure as a side effect.
- Cellular ProtectionLab or animal research only
Catechins protect cells from oxidation in laboratory studies; no human trial we read shows that supplements deliver this benefit.
- Heart HealthPreliminary or mixed
No trial reported heart events. Green tea lowered LDL and blood pressure in a few small trials, so evidence is limited.
Body systems (4)
- Hepatic / Liver SystemDocumented risk
Liver injury is uncommon but has been reported with green tea extract capsules and tablets; the US Pharmacopeia asks labels to say stop and see a practitioner if liver symptoms appear.
- Liver & DetoxDocumented risk
Liver injury is uncommon but has been reported with green tea extract capsules and tablets; the US Pharmacopeia asks labels to say stop and see a practitioner if liver symptoms appear.
- Cardiovascular SystemPreliminary or mixed
Green tea lowered LDL and blood pressure in a few small trials, but no trial measured heart disease events.
- Metabolism & WeightPreliminary or mixed
Catechins and caffeine are thought to raise energy use, but trial weight loss was small and not clinically important.
Body parts (2)
- LiverDocumented risk
EFSA found trials of 800 mg or more EGCG a day as a supplement raised liver enzyme markers; this describes trial results, not a recommended amount.
- HeartPreliminary or mixed
Observed links to lower coronary heart disease risk were seen in Asian but not Western populations; trials did not report heart events.
Functional actions (1)
- AntioxidantLab or animal research only
Green tea catechins are strong antioxidants in the laboratory. That does not show that taking extract prevents disease.
Root causes (2)
- Medication Side EffectsDocumented risk
Green tea or its extract lowered blood levels of nadolol and atorvastatin and interacted with raloxifene, so it may change how some medicines work.
- Oxidative StressLab or animal research only
Catechins act as antioxidants in the lab. Whether extract reduces oxidative stress in people in a way that matters for health is not shown by the sources read.
Biomarkers (3)
- ALTDocumented risk
Liver enzyme markers such as ALT rose in trials of high-dose EGCG supplements, which is why liver tests are used to watch for harm.
- ASTDocumented risk
Liver enzyme markers such as AST rose in trials of high-dose EGCG supplements, which is why liver tests are used to watch for harm.
- LDL CholesterolPreliminary or mixed
Green tea lowered LDL cholesterol modestly in trials, but few trials contributed and results were not stable.
Conditions & symptoms (1)
- Drug-Induced Liver DiseaseDocumented risk
Liver injury has been reported in people using green tea extract supplements; it is uncommon, and some people may be more susceptible because of genes.
Documented risks and interactions (3)
- Liver safety caution. Liver injury is uncommon but has been reported with green tea extract capsules and tablets, mainly extracts rather than brewed tea.
- Interaction with medicines. High-dose green tea lowered blood levels of nadolol, extract lowered atorvastatin levels, and green tea interacted with raloxifene.
- Caffeine and other side effects. Extract can cause nausea, constipation, abdominal discomfort and higher blood pressure; tea contains caffeine.
Liver warning signs come first
Liver injury is uncommon but has been reported in people who used green tea products, mainly green tea extracts in tablet or capsule form. [1] A United States Pharmacopeia (USP) labeling caution for green tea extract says to stop use and consult a healthcare practitioner if liver trouble symptoms appear, such as abdominal pain, dark urine or jaundice (yellowing of the skin or eyes). [2] If you have those symptoms, contact a clinician promptly.Brewed tea and extract are different products
Green tea is made from the leaves of Camellia sinensis without fermentation. Most of its polyphenols are catechins, and EGCG is the most relevant one. [3] This page covers supplements and the tea comparison; the plant itself is in the green tea herb guide.| Brewed green tea | Extract capsule or tablet | |
|---|---|---|
| EGCG amounts | In EU adults, mean intake from tea infusions was 90 to 300 mg a day, and up to 866 mg a day for high-level consumers (EFSA, 2018). [3] | Food supplements provided 5 to 1,000 mg EGCG a day for adults (EFSA, 2018). [3] |
| Safety statements | NCCIH reports no safety concerns for tea as a beverage in adults, but it contains caffeine. [1] EFSA considered traditionally prepared tea generally safe at reported European intakes, with rare liver cases most probably an individual (idiosyncratic) reaction. [3] | Side effects include nausea, constipation, abdominal discomfort and increased blood pressure; liver injury is uncommon but reported. [1] |
What is reported about the liver
- EFSA (EU, 2018). Interventional trials showed that doses of 800 mg EGCG a day or more, taken as a food supplement, raised serum transaminases (liver enzyme markers) compared with control. [3] This describes trial results. It is not a recommended amount.
- Trial amounts. Sloan Kettering cites clinical data that 200 mg EGCG twice daily for one year was safe, while 800 mg daily was associated with elevated liver enzymes. [4]
- USP review (2020). Case reports linked liver injury to EGCG intakes from 140 mg to about 1,000 mg a day, with large differences between people, possibly due to genetic factors. [2] Repeated bolus doses of extract during fasting raised catechin absorption. [2] Solvent residues, pesticides and metals were not found to be involved in the injuries reviewed. [2]
- Earlier USP review (2008). Of 216 case reports on green tea products, 34 concerned liver damage; 27 were rated possible and 7 probable. [5]
- Genes. NCCIH says people with a specific immune-related gene variant appear especially susceptible, and 5 to 15 percent of Americans carry it. [1]
Case reports cannot show how often injury happens. See liver safety and supplements.
What trials found for benefits
Labels used here: promising but limited, mixed and insufficient evidence. Antioxidant activity seen in the lab is not the same as these outcomes.| Question | What the source found | Label |
|---|---|---|
| Weight loss | A Cochrane review of trials lasting at least 12 weeks in overweight or obese adults found small, non-significant weight loss, unlikely to be clinically important. [6] | Mixed |
| Cholesterol | Small drops in total and LDL cholesterol with no change in HDL or triglycerides; most trials used extract supplements. [1] | Promising but limited |
| Heart disease and blood pressure | A Cochrane review found no trial reporting cardiovascular events. Green tea lowered LDL and blood pressure, but few trials contributed and results were not stable. [7] | Promising but limited |
| Cancer prevention | A Cochrane review found inconsistent results and limited evidence; extract trials reported stomach upset and raised liver enzymes. [8] | Insufficient evidence |
Medicines, pregnancy and other cautions
- Medicines. High-dose green tea reduced blood levels of nadolol, extract reduced atorvastatin levels, and green tea interacted with raloxifene. [1] Sloan Kettering says EGCG can inhibit the effect of bortezomib and similar cancer drugs, and that green tea can affect iron absorption. [4]
- Pregnancy and breastfeeding. NCCIH says caffeine intake should stay moderate in pregnancy and that caffeine passes into breast milk. [1] Sloan Kettering advises not drinking green tea while pregnant or breastfeeding. [4]
- Children, kidney disease, surgery. Not described in the sources we read, except that moderate tea intake was not linked to kidney stones. [4] Tell your surgeon about any supplement; see supplements before surgery.
- Quality. Extract catechin profiles vary with manufacturing. [2] See quality testing and certifications and medication interactions.
Ask a clinician or pharmacist before using an extract, especially with a liver condition or regular medicines. For tea in the wider diet, see polyphenol-rich foods and drinks.
Frequently asked questions
Is green tea extract riskier than drinking green tea?
Liver injury was reported primarily with extracts in tablet or capsule form, while no safety concerns were reported for tea as a beverage in adults. [1]
At what amount does EGCG affect the liver?
EFSA found that 800 mg EGCG a day or more as a supplement raised liver enzyme markers in trials. [3] USP noted case reports starting from 140 mg a day. [2]
Does green tea extract help with weight loss?
A Cochrane review found a small, non-significant effect that is unlikely to matter clinically. [6]
Should extract be taken on an empty stomach?
USP found that repeated bolus doses during fasting raised catechin absorption, and its label caution says not to take the extract on an empty stomach. [2] Ask a pharmacist about your product.
Can I take it with my medicines?
Not always. NCCIH and Sloan Kettering list interactions including nadolol, atorvastatin, raloxifene and bortezomib. [1][4]
References
- Green Tea: Usefulness and Safety. National Center for Complementary and Integrative Health (US). Read 2026-10-23.
- United States Pharmacopeia (USP) comprehensive review of the hepatotoxicity of green tea extracts. Toxicology reports (2020). PubMed abstract. Read 2026-10-23.
- Scientific opinion on the safety of green tea catechins. EFSA journal. European Food Safety Authority (2018). PubMed abstract. EFSA full text was not readable (HTTP 403); abstract read on PubMed. Read 2026-10-23.
- Green Tea. Memorial Sloan Kettering Cancer Center, About Herbs (US). Read 2026-10-23.
- Safety of green tea extracts : a systematic review by the US Pharmacopeia. Drug safety (2008). PubMed abstract. Read 2026-10-23.
- Green tea for weight loss and weight maintenance in overweight or obese adults. The Cochrane database of systematic reviews (2012). PubMed abstract. Read 2026-10-23.
- Green and black tea for the primary prevention of cardiovascular disease. The Cochrane database of systematic reviews (2013). PubMed abstract. Read 2026-10-23.
- Green tea (Camellia sinensis) for the prevention of cancer. The Cochrane database of systematic reviews (2020). PubMed abstract. Read 2026-10-23.