Key findings from detailed records
Population: Analysis of 1,021 women with normal baseline liver enzymes from a trial involving 1,075 women Findings: Moderate or more severe liver test abnormalities occurred in 5.1% of the extract group. Odds ratio versus control: 7.0 (95% CI 2.4–20.3).
KNOWLEDGE RECORD
- Category
- Metabolism and cellular function
- Last Reviewed
Names and related search termsEGCG and tea catechins / EGCG / Epigallocatechin gallate / Tea catechins / Green tea extract
Study type: human intervention study.
OUTCOME-SPECIFIC EVIDENCE
Scientific Evidence Profile
Assessment pending
An outcome-specific assessment has not yet been completed. This is not a finding that the ingredient is ineffective. The study records below remain available.
This profile concerns the stated outcome and population, not the ingredient as a whole. It is not a probability of benefit, a safety rating, a product efficacy rating or an indication of product adoption.
How we assess evidenceIngredient Profile
- What is it?
- EGCG is a polyphenol formed from epigallocatechin and gallic acid. It is one specific catechin, not a synonym for every compound in tea. [1]
Sources for this profile
Compound properties and formulation properties are different. These sources do not establish the efficacy of a finished supplement.
- PubChem — Epigallocatechin Gallate (CID 65064) Chemical identity reference. Maintained by NCBI, U.S. National Library of Medicine. Database record; not a clinical trial.
Profile sources checked:
Read the evidence in context
- Evidence: what was measured in the stated population or experimental model.
- Inference: an interpretation connecting findings; its applicability depends on the study conditions.
- Hypothesis: a proposed explanation or effect that remains to be tested.
Why It Matters #
What safety data exist for high-dose green tea extracts? Check the detailed records for study conditions and use the literature map to compare other populations and outcomes.
What Was Studied #
Analysis of 1,021 women with normal baseline liver enzymes from a trial involving 1,075 women Liver function analysis of a double-blind placebo-controlled RCT. Outcomes: Liver measures including ALT and AST. The parent trial concerned breast cancer risk-related measures.[1]
What Was Found #
Moderate or more severe liver test abnormalities occurred in 5.1% of the extract group. Odds ratio versus control: 7.0 (95% CI 2.4–20.3).[1]
What the Evidence Means #
Results concern a specific high-dose extract. Exposure differs from ordinary tea drinking, and the same risk cannot be assigned to all catechin use.[1]
Comparing similar populations, formulations, durations and outcomes helps identify where findings agree and where they differ.
What We Can Learn #
“Antioxidant” and “natural” do not establish safety. Give adverse events the same attention as benefits.
What Remains Unknown #
Further questions include reproducibility across populations and formulations, and the long-term balance of benefits and harms. Use the literature map as a starting point for these questions.
LITERATURE MAP / 10 PAPERS
Compare papers by conditions and findings.
A literature map covering different populations, outcomes and formulations. Read alongside detailed records to avoid treating one trial as the conclusion for an entire ingredient.
Selected: 2026-09-21. Bibliographic information checked against Europe PMC / PubMed. Editorial selection considered major papers and a range of populations and questions. This is not a systematic search covering all recent research.
10 RECORDS
A dash marks fields outside the bibliographic record. Use detailed records to compare findings and design records to connect mechanisms.
No papers match. Change the search conditions.
The literature map is an index of research questions and references. Individual assessment of results, doses, funding and COI is limited to the detailed study records. Related reports from the same trial may be included; paper counts are not counts of independent trials.
Explore the research Study Records
Listed doses describe study conditions, not recommended intake.
Effect of Green Tea Supplements on Liver Enzyme Elevation: Results from a Randomized Intervention Study in the United States.
PubMed 28765194DOI: 10.1158/1940-6207.capr-17-0160
- Authors
- Yu Z, Samavat H, Dostal AM, Wang R, Torkelson CJ, Yang CS, Butler LM, Kensler TW, Wu AH, Kurzer MS, Yuan JM.
- Journal
- Cancer prevention research (Philadelphia, Pa.)
- Publication year
- 2017
- Study design
- Liver function analysis of a double-blind placebo-controlled RCT
- Participants
- Analysis of 1,021 women with normal baseline liver enzymes from a trial involving 1,075 women
- Dose and intervention
- Green tea extract: 4 capsules/day for 12 months, providing mean total catechins 1315 mg/day, including EGCG 843 mg/day. 2 capsules with breakfast and 2 with dinner. Composition verified in the full-text Methods.
- Duration
- 12 months
- Outcomes and their role in the study
- Liver measures including ALT and AST. The parent trial concerned breast cancer risk-related measures.
- Findings
- Moderate or more severe liver test abnormalities occurred in 5.1% of the extract group. Odds ratio versus control: 7.0 (95% CI 2.4–20.3).
- Limitations
- Results concern a specific high-dose extract. Exposure differs from ordinary tea drinking, and the same risk cannot be assigned to all catechin use.
- Funding
- US National Cancer Institute and Department of Defense/US Army Medical Research support. Corban Laboratories/Eniva Nutraceutics supplied the study supplement.
- Conflict of Interest
- Not verified within the scope of this review. This does not mean “no funding” or “no conflicts of interest.”
- Scope of source review
- The original abstract was checked for population, dose, duration and results; available source disclosures were checked separately. Any unverified disclosure details remain identified above.
Cite this page
LÍFSVARÐA. EGCG and tea catechins: What safety data exist for high-dose green tea extracts? Version 1.1 / Updated 2026-10-24
https://lifsvarda.com/knowledge/egcg/Edited by LÍFSVARÐA (product brand).Editorial policy
Safety and interactions
The liver-safety findings summarized here concern a concentrated green tea extract taken for 12 months, with a mean daily EGCG dose of 843 mg. The trial monitored liver tests and stopped supplementation when prespecified abnormalities occurred. This is a study exposure, not a recommended intake or a threshold below which all extracts are safe. Ordinary tea drinking and concentrated extracts require separate assessment.
Safety section reviewed: 2026-10-24.
Sources and updates
- Yu Z, Samavat H, Dostal AM, Wang R, Torkelson CJ, Yang CS, Butler LM, Kensler TW, Wu AH, Kurzer MS, Yuan JM. (2017). Effect of Green Tea Supplements on Liver Enzyme Elevation: Results from a Randomized Intervention Study in the United States.The original abstract was checked for population, dose, duration and results; available source disclosures were checked separately. Any unverified disclosure details remain identified above.
First published: 2026-09-21 / Version 1.1. Updated 2026-09-23: Added a research comparison table and links to design records. Source notes identify the scope of verification when the full paper has not been reviewed. Research summaries and LÍFSVARÐA’s interpretation are distinguished.