The Science of Green Tea Extract: A Simple Guide to Its Benefits and Risks

Written By Ingrid Huddleston

You’ve likely heard the buzz around green tea, but its concentrated cousin, Green Tea Extract (GTE), is what’s getting significant attention in the health and wellness world. Available in convenient capsules, GTE delivers a potent dose of the plant’s beneficial compounds. But what does the science say about its effects? Let’s break it down.

How Does It Work?

The power of Green Tea Extract comes from its high concentration of polyphenols, particularly a catechin called epigallocatechin gallate, or EGCG. Think of EGCG as a powerful antioxidant that works on a cellular level. It helps protect your body from oxidative stress, which is damage caused by unstable molecules called free radicals. This antioxidant action also helps calm inflammation, a root cause of many chronic health issues. Some studies also suggest it can gently boost metabolism, which is why it’s a popular ingredient in fat-burning supplements.

What Are the Clinically Studied Benefits?

While GTE is studied for many uses, the evidence is strongest in a few key areas:

  • Cardiovascular Health: This is where GTE shows the most promise. Multiple high-quality reviews of human trials have found that GTE supplementation can significantly lower total and LDL ("bad") cholesterol levels, which are major risk factors for heart disease.

  • Weight Management: The results here are more modest. Some studies show that GTE can lead to a small but significant reduction in body weight and waist circumference, especially when combined with a healthy diet and regular exercise. However, other major reviews have found the effect is too small to be clinically important, so it’s best viewed as a supportive aid rather than a primary weight loss solution.

  • Brain Health: Research into GTE for cognitive function is still emerging. While some small studies suggest it may help improve memory and brain connectivity, more long-term research is needed to make definitive claims.

Who Might Benefit?

Based on the evidence, Green Tea Extract could be a useful addition for:

  • Individuals looking for natural support for their cardiovascular health, particularly for managing cholesterol levels.

  • People who are already following a healthy diet and exercise plan and want a modest boost for their weight management goals.

Important Safety Considerations

This is the most critical part: while generally well-tolerated, GTE supplements carry a rare but serious risk of liver injury, a risk not associated with drinking brewed green tea.

To use it safely, follow these guidelines:

  • Always take GTE with a meal. Taking it on an empty stomach can dramatically increase the concentration of compounds hitting your liver at once, which has been linked to a higher risk of adverse effects.

  • Avoid GTE if you have a pre-existing liver condition.

  • Talk to your doctor before taking GTE, especially if you are pregnant, breastfeeding, or taking medications like blood thinners or statins.

The Bottom Line

Green Tea Extract is a supplement with promising, science-backed potential, especially for supporting heart health. However, it is not a magic pill. Its benefits are best realized when it is used correctly and as part of a broader health plan that includes a balanced diet and consistent physical activity. By understanding both its benefits and its risks, you can make an informed decision about whether it’s the right choice for you.

  • Green Tea Extract (GTE) is a concentrated form of green tea available in capsules. Its power comes from polyphenols, particularly EGCG (epigallocatechin gallate), a potent antioxidant that:

    • Protects cells from oxidative stress

    • Helps calm inflammation

    • May provide a gentle metabolic boost

    • Cardiovascular Health: Strongest evidence. Multiple human studies show GTE can lower total and LDL (“bad”) cholesterol, reducing heart disease risk factors.

    • Weight Management: Provides a small, modest effect on body weight and waist size, especially with a healthy diet and exercise. Results are supportive, not transformative.

    • Brain Health: Early studies suggest potential benefits for memory and brain connectivity, but more research is needed.

    • People looking for natural support for heart health and cholesterol management

    • Individuals already maintaining a healthy lifestyle who want modest weight management support

    • Rare but serious risk of liver injury, which is not seen with brewed green tea

    • Always take GTE with a meal to reduce liver stress

    • Avoid if you have a liver condition

    • Consult your doctor if pregnant, breastfeeding, or taking medications like statins or blood thinners

Works Cited

  1. Green Tea Polyphenol (-)-Epigallocatechin-3-Gallate (EGCG): A ..., accessed June 30, 2025, https://www.mdpi.com/2076-3921/11/8/1566

  2. Tea | Linus Pauling Institute | Oregon State University, accessed June 30, 2025, https://lpi.oregonstate.edu/mic/food-beverages/tea

  3. Green Tea Catechins: Biologic Properties, Proposed Mechanisms of Action, and Clinical Implications - JDDonline, accessed June 30, 2025, https://jddonline.com/articles/green-tea-catechins-biologic-properties-proposed-mechanisms-of-action-and-clinical-implications-S1545961612E0055X

  4. Therapeutic Effects of Green Tea Polyphenol (‒)-Epigallocatechin-3 ..., accessed June 30, 2025, https://pmc.ncbi.nlm.nih.gov/articles/PMC9820274/

  5. Beneficial Properties of Green Tea Catechins - MDPI, accessed June 30, 2025, https://www.mdpi.com/1422-0067/21/5/1744

  6. Green Tea Catechins and Sport Performance - Antioxidants in Sport Nutrition - NCBI, accessed June 30, 2025, https://www.ncbi.nlm.nih.gov/books/NBK299060/

  7. Function of Green Tea Catechins in the Brain: Epigallocatechin Gallate and its Metabolites, accessed June 30, 2025, https://www.mdpi.com/1422-0067/20/15/3630

  8. Epigallocatechin-3-gallate (EGCG): Chemical and biomedical perspectives - PMC, accessed June 30, 2025, https://pmc.ncbi.nlm.nih.gov/articles/PMC2903211/

  9. Therapeutic effect of high-dose green tea extract on weight reduction: A randomized, double-blind, placebo-controlled clinical trial - ResearchGate, accessed June 30, 2025, https://www.researchgate.net/publication/277980906_Therapeutic_effect_of_high-dose_green_tea_extract_on_weight_reduction_A_randomized_double-blind_placebo-controlled_clinical_trial

  10. The Catechins Profile of Green Tea Extracts Affects the Antioxidant Activity and Degradation of Catechins in DHA-Rich Oil - MDPI, accessed June 30, 2025, https://www.mdpi.com/2076-3921/11/9/1844

  11. Epigallocatechin gallate – Knowledge and References - Taylor & Francis, accessed June 30, 2025, https://taylorandfrancis.com/knowledge/Engineering_and_technology/Chemical_engineering/Epigallocatechin_gallate/

  12. Green Tea Extract benefits, dosage, and side effects - Examine.com, accessed June 30, 2025, https://examine.com/supplements/green-tea-extract/

  13. Comparative Study of Composition and Antioxidant Properties of Green Tea Extracts from Different Commercial Grades | ACS Food Science & Technology, accessed June 30, 2025, https://pubs.acs.org/doi/10.1021/acsfoodscitech.5c00068

  14. EGCg Green Tea Extract 400 mg Veg Capsules - NOW Foods, accessed June 30, 2025, https://www.nowfoods.com/products/supplements/egcg-green-tea-extract-400-mg-veg-capsules

  15. How Much Green Tea Extract Is Needed For Weight Loss? - Swolverine, accessed June 30, 2025, https://swolverine.com/blogs/blog/green-tea-weight-loss

  16. What is more effective for weight loss, green tea extract or raw green tea leaves? - Quora, accessed June 30, 2025, https://www.quora.com/What-is-more-effective-for-weight-loss-green-tea-extract-or-raw-green-tea-leaves

  17. Green Tea Catechins and Cardiovascular Health: An Update - PMC - PubMed Central, accessed June 30, 2025, https://pmc.ncbi.nlm.nih.gov/articles/PMC2748751/

  18. Epigallocatechin Gallate (EGCG): Pharmacological Properties, Biological Activities and Therapeutic Potential - MDPI, accessed June 30, 2025, https://www.mdpi.com/1420-3049/30/3/654

  19. Effects of Dosing Condition on the Oral Bioavailability of Green Tea Catechins after Single-Dose Administration of Polyphenon E in Healthy Individuals - AACR Journals, accessed June 30, 2025, https://aacrjournals.org/clincancerres/article/11/12/4627/185571/Effects-of-Dosing-Condition-on-the-Oral

  20. Catechins: Protective mechanism of antioxidant stress in atherosclerosis - Frontiers, accessed June 30, 2025, https://www.frontiersin.org/journals/pharmacology/articles/10.3389/fphar.2023.1144878/full

  21. 10 Benefits of Green Tea Extract - Healthline, accessed June 30, 2025, https://www.healthline.com/nutrition/10-benefits-of-green-tea-extract

  22. (PDF) Pharmacological Actions and Underlying Mechanisms of Catechin: A Review, accessed June 30, 2025, https://www.researchgate.net/publication/354360660_Pharmacological_Actions_and_Underlying_Mechanisms_of_Catechin_A_Review

  23. (PDF) The Role of Epigallocatechin Gallate (EGCG) in Human Health: A Comprehensive Review - ResearchGate, accessed June 30, 2025, https://www.researchgate.net/publication/387997866_The_Role_of_Epigallocatechin_Gallate_EGCG_in_Human_Health_A_Comprehensive_Review

  24. EGCG (Epigallocatechin Gallate): Benefits, Dosage, and Safety - Healthline, accessed June 30, 2025, https://www.healthline.com/nutrition/egcg-epigallocatechin-gallate

  25. 12 Best Foods for Arthritis, accessed June 30, 2025, https://www.arthritis.org/health-wellness/healthy-living/nutrition/healthy-eating/12-best-foods-for-arthritis

  26. Molecular Mechanisms of the Anti-Inflammatory Effects of Epigallocatechin 3-Gallate (EGCG) in LPS-Activated BV-2 Microglia Cells - MDPI, accessed June 30, 2025, https://www.mdpi.com/2076-3425/13/4/632

  27. Molecular Mechanisms of Green Tea Polyphenols - PMC - PubMed Central, accessed June 30, 2025, https://pmc.ncbi.nlm.nih.gov/articles/PMC3769684/

  28. Mechanisms of Body Weight Reduction and Metabolic Syndrome Alleviation by Tea - PMC, accessed June 30, 2025, https://pmc.ncbi.nlm.nih.gov/articles/PMC4991829/

  29. Does green tea catechin enhance weight-loss effect of exercise training in overweight and obese individuals? a systematic review and meta-analysis of randomized trials - Taylor & Francis Online, accessed June 30, 2025, https://www.tandfonline.com/doi/full/10.1080/15502783.2024.2411029

  30. A 60-Day Green Tea Extract Supplementation Counteracts the Dysfunction of Adipose Tissue in Overweight Post-Menopausal and Class I Obese Women - MDPI, accessed June 30, 2025, https://www.mdpi.com/2072-6643/14/24/5209

  31. The effects of green tea extract supplementation on body ... - PubMed, accessed June 30, 2025, https://pubmed.ncbi.nlm.nih.gov/38031409/

  32. The effect of green tea supplementation on obesity: A systematic review and dose-response meta-analysis of randomized controlled trials - PubMed, accessed June 30, 2025, https://pubmed.ncbi.nlm.nih.gov/32372444/

  33. The effects of green tea on weight loss and weight maintenance: a meta-analysis - PubMed, accessed June 30, 2025, https://pubmed.ncbi.nlm.nih.gov/19597519/

  34. The effects of green tea extract supplementation on body composition, obesity-related hormones and oxidative stress markers: a grade-assessed systematic review and dose–response meta-analysis of randomised controlled trials | British Journal of Nutrition, accessed June 30, 2025, https://www.cambridge.org/core/journals/british-journal-of-nutrition/article/effects-of-green-tea-extract-supplementation-on-body-composition-obesityrelated-hormones-and-oxidative-stress-markers-a-gradeassessed-systematic-review-and-doseresponse-metaanalysis-of-randomised-controlled-trials/5F7DCFF04BE51796D39A6CC5B0A3089A

  35. Therapeutic effect of high-dose green tea extract on weight reduction: A randomized, double-blind, placebo-controlled clinical trial - PubMed, accessed June 30, 2025, https://pubmed.ncbi.nlm.nih.gov/26093535/

  36. Green tea for weight loss and weight maintenance in overweight or ..., accessed June 30, 2025, https://pubmed.ncbi.nlm.nih.gov/23235664/

  37. Green tea for weight loss and weight maintenance in overweight or obese adults - PMC, accessed June 30, 2025, https://pmc.ncbi.nlm.nih.gov/articles/PMC8406948/

  38. Long-term supplementation of decaffeinated green tea extract does not modify body weight or abdominal obesity in a randomized trial of men at high risk for prostate cancer - Oncotarget, accessed June 30, 2025, https://www.oncotarget.com/article/18858/text/

  39. Effect of green tea or green tea extract consumption on body weight and body composition; systematic review and meta-analysis - NCBI, accessed June 30, 2025, https://www.ncbi.nlm.nih.gov/books/NBK231811/

  40. From a Cup of Tea to Cardiovascular Care: Vascular Mechanisms of Action - PMC, accessed June 30, 2025, https://pmc.ncbi.nlm.nih.gov/articles/PMC11433009/

  41. Green tea consumption and risk of cardiovascular and ischemic ..., accessed June 30, 2025, https://pubmed.ncbi.nlm.nih.gov/26318390/

  42. The effects of green tea supplementation on cardiovascular risk ..., accessed June 30, 2025, https://pubmed.ncbi.nlm.nih.gov/36704803/

  43. The effects of green tea supplementation on cardiovascular risk factors: A systematic review and meta-analysis - PubMed Central, accessed June 30, 2025, https://pmc.ncbi.nlm.nih.gov/articles/PMC9871939/

  44. Effect of green tea supplementation on blood pressure among overweight and obese adults: a protocol for a systematic review | BMJ Open, accessed June 30, 2025, https://bmjopen.bmj.com/content/4/4/e004971

  45. Green Tea Suppresses Brain Aging - PMC, accessed June 30, 2025, https://pmc.ncbi.nlm.nih.gov/articles/PMC8401650/

  46. Epigallocatechin-3-gallate Enhances Cognitive and Memory Performance and Protects Against Brain Injury in Methionine-induced Hyperhomocysteinemia Through Interdependent Molecular Pathways - PubMed Central, accessed June 30, 2025, https://pmc.ncbi.nlm.nih.gov/articles/PMC9797462/

  47. Neuroprotective insights into epigallocatechin gallate (EGCG) for neurodegenerative disorders - Open Exploration Publishing, accessed June 30, 2025, https://www.explorationpub.com/Journals/en/Article/100673

  48. Epigallocatechin-3-Gallate (EGCG): New Therapeutic Perspectives for Neuroprotection, Aging, and Neuroinflammation for the Modern Age - PubMed Central, accessed June 30, 2025, https://pmc.ncbi.nlm.nih.gov/articles/PMC8945730/

  49. 10 Evidence-Based Benefits of Green Tea - Healthline, accessed June 30, 2025, https://www.healthline.com/nutrition/top-10-evidence-based-health-benefits-of-green-tea

  50. The Association between Green Tea Consumption and Cognitive Function: A Meta-Analysis of Current Evidence - PubMed, accessed June 30, 2025, https://pubmed.ncbi.nlm.nih.gov/39947165/

  51. Acute effects of (–)-gallocatechin gallate-rich green tea extract on the cerebral hemodynamic response of the prefrontal cortex in healthy humans - Frontiers, accessed June 30, 2025, https://www.frontiersin.org/journals/neuroergonomics/articles/10.3389/fnrgo.2023.1136362/full

  52. Green Tea Consumption Affects Cognitive Dysfunction in the Elderly: A Pilot Study - PMC, accessed June 30, 2025, https://pmc.ncbi.nlm.nih.gov/articles/PMC4210905/

  53. Green tea extract enhances parieto-frontal connectivity during working memory processing, accessed June 30, 2025, https://pmc.ncbi.nlm.nih.gov/articles/PMC4159594/

  54. Epigallocatechin Gallate (EGCG) - Alzheimer's Drug Discovery Foundation, accessed June 30, 2025, https://www.alzdiscovery.org/uploads/cognitive_vitality_media/EGCG-Cognitive-Vitality-For-Researchers.pdf

  55. EGCG & Your Brain | Cognitive Vitality - Alzheimer's Drug Discovery Foundation, accessed June 30, 2025, https://www.alzdiscovery.org/cognitive-vitality/ratings/egcg

  56. Green Tea Extract Powder (EGCG) - The Formulator Shop, accessed June 30, 2025, https://theformulatorshop.com/product/green-tea-extract/

  57. Randomized, placebo-controlled trial evaluating the safety of one-year administration of green tea catechins - PubMed Central, accessed June 30, 2025, https://pmc.ncbi.nlm.nih.gov/articles/PMC5340117/

  58. Green Tea: Usefulness and Safety | NCCIH, accessed June 30, 2025, https://www.nccih.nih.gov/health/green-tea

  59. Green Tea Extract - Content - Health Encyclopedia - University of Rochester Medical Center, accessed June 30, 2025, https://www.urmc.rochester.edu/encyclopedia/content?contenttypeid=19&contentid=greenteaextract

  60. Green Tea: Side Effects, Uses, Dosage, Interactions, Warnings - RxList, accessed June 30, 2025, https://www.rxlist.com/green_tea/generic-drug.htm

  61. March 12, 2021: What are the Adverse Effects of Green Tea Extract?, accessed June 30, 2025, https://www.vumc.org/poison-control/toxicology-question-week/march-12-2021-what-are-adverse-effects-green-tea-extract

  62. GREEN TEA: Overview, Uses, Side Effects, Precautions, Interactions, Dosing and Reviews, accessed June 30, 2025, https://www.webmd.com/vitamins/ai/ingredientmono-960/green-tea

  63. Green Tea Pills (Supplement): Uses & Side Effects - Cleveland Clinic, accessed June 30, 2025, https://my.clevelandclinic.org/health/drugs/20553-green-tea-oral-dosage-forms

  64. Green Tea - LiverTox - NCBI Bookshelf, accessed June 30, 2025, https://www.ncbi.nlm.nih.gov/books/NBK547925/

  65. Green tea extract–associated acute liver injury: Case report and review - PMC, accessed June 30, 2025, https://pmc.ncbi.nlm.nih.gov/articles/PMC9745259/

  66. Hepatotoxicity of Green Tea Extract: Idiosyncratic or Indirect Drug-induced Liver Injury?, accessed June 30, 2025, https://www.xiahepublishing.com/2835-6357/FIM-2022-00034

  67. Effect of Green Tea Supplements on Liver Enzyme Elevation: Results from a Randomized Intervention Study in the United States - AACR Journals, accessed June 30, 2025, https://aacrjournals.org/cancerpreventionresearch/article/10/10/571/112911/Effect-of-Green-Tea-Supplements-on-Liver-Enzyme

  68. Summary Safety Review - Green tea extract-containing natural health products - Assessing the potential risk of liver injury (hepatotoxicity) - Canada.ca, accessed June 30, 2025, https://www.canada.ca/en/health-canada/services/drugs-health-products/medeffect-canada/safety-reviews/green-tea-extract-containing-natural-health-products-assessing-potential-risk-liver-injury.html

  69. Acute effects of tea constituents L-theanine, caffeine, and epigallocatechin gallate on cognitive function and mood: a systematic review and meta-analysis - PubMed, accessed June 30, 2025, https://pubmed.ncbi.nlm.nih.gov/24946991/

  70. Research Breakdown on Green Tea Extract - Examine.com, accessed June 30, 2025, https://examine.com/supplements/green-tea-extract/research/

Content Disclaimer

This information was generated and formatted using AI technology to summarize and present current scientific research on the specified supplement. While every effort has been made to ensure accuracy, clarity, and relevance, the information provided should not be considered a substitute for professional medical advice. All health claims are supported by citations from peer-reviewed studies and credible sources, which have been included for transparency and verification. Always consult a qualified healthcare provider before making decisions related to supplement use or health interventions.

Ingrid Huddleston
Next

What Is Betaine HCl? A Guide to This Digestive Supplement