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Green Tea

Green tea is most recognized for its antioxidant content and perceived health benefits.

Evidence · Grade D
Meta-analysis availableSystematic review availableHuman trial evidenceTraditional useInteraction riskNeeds more research

A lightly oxidized tea rich in catechins, studied for metabolism, skin, and longevity.

Green tea, derived from the Camellia sinensis plant, is a widely consumed beverage globally. It is commonly valued for its potential health-supporting properties, which are often attributed to its rich content of polyphenols, particularly catechins. Traditionally, it has been used for various purposes, and it is typically consumed as a brewed drink, though extracts are also available.

Quick answer

Evidence Summary

Evidence · Grade D

Current evidence for many of green tea's purported benefits comes from observational studies, in vitro research, and some human clinical trials. However, the existing clinical studies are often small or have methodological limitations, contributing to its Grade D evidence rating.

Last reviewed · Jun 2026

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Why It Works

Green tea appears to exert its effects primarily through its antioxidant and anti-inflammatory compounds, which may help protect cells from damage and modulate various biological pathways.

How it works in more detail

The main active compounds, catechins (especially epigallocatechin gallate or EGCG), appear to act as potent antioxidants, neutralizing free radicals and reducing oxidative stress. EGCG has been studied for its potential to inhibit 5-alpha reductase and matrix metalloproteinases, which are enzymes implicated in processes such as skin aging. Further, green tea compounds may influence cellular signaling pathways and gene expression, as observed in some preclinical models.

How to use

Always consult a qualified clinician.

Editorial guidance

Suggested dosage
2–3 cups/day brewed, or 300–500 mg/day of standardized EGCG extract.
Research dosage range
300-1000 mg/day of EGCG, or 3-5 cups of brewed green tea daily
Typical onset
Some acute effects, such as a mild stimulant effect due to caffeine, may be felt relatively quickly. However, any sustained health benefits from green tea are generally thought to require consistent, long-term consumption over weeks to months.
Typical forms
tea bags, loose leaf tea, capsule, extract
Quality markers
For green tea supplements, look for products standardized to a specific percentage of catechins, particularly EGCG, to ensure consistent potency. Reputable brands often provide third-party testing for purity and absence of contaminants. Organic certification may indicate fewer pesticide residues.
Medication interactions
  • anticoagulants (may increase bleeding risk)
  • stimulants (additive effects)
  • medications metabolized by CYP450 enzymes (potential for altered metabolism)
  • iron supplements (may reduce absorption)
Avoid if
  • pregnant or breastfeeding (high doses)
  • liver conditions (high doses of extracts)
  • iron deficiency anemia (may inhibit iron absorption)
  • anxiety disorders (due to caffeine sensitivity)

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Suggested dosage

2–3 cups/day brewed, or 300–500 mg/day of standardized EGCG extract.

General guidance — discuss specifics with a clinician.

Active medicinal compounds

EGCG, EGC, ECG, L-theanine, caffeine.

Nutritional contents

Polyphenols, small amount of caffeine, L-theanine.

Traditional use

Central to Chinese and Japanese medicine and ceremony for over 1,000 years.

Safety

Safety warnings

High doses of EGCG extracts have been linked to liver toxicity. Brewed tea is generally safe.

Avoid if

  • pregnant or breastfeeding (high doses)
  • liver conditions (high doses of extracts)
  • iron deficiency anemia (may inhibit iron absorption)
  • anxiety disorders (due to caffeine sensitivity)

Medication interactions

  • anticoagulants (may increase bleeding risk)
  • stimulants (additive effects)
  • medications metabolized by CYP450 enzymes (potential for altered metabolism)
  • iron supplements (may reduce absorption)

Reported side effects

  • gastrointestinal upset
  • headache
  • dizziness
  • insomnia (due to caffeine)

General guidance — discuss specifics with a clinician.

Evidence ecosystem

Scientific literature, clinical guidance, government sources, ongoing research, traditional use, and lived experience — grouped by source type and quality.

Overall grade (D)

Current evidence for many of green tea's purported benefits comes from observational studies, in vitro research, and some human clinical trials. However, the existing clinical studies are often small or have methodological limitations, contributing to its Grade D evidence rating.

Filter by source type

Meta-Analyses(1)

Pooled analyses across multiple human trials.

Very High Quality
  • Dietary Strategies for Weight Loss Maintenance.

    van Baak MA, Mariman ECM · Nutrients · 2019 · n=2875

    Weight regain after a successful weight loss intervention is very common. Most studies show that, on average, the weight loss attained during a weight loss intervention period is not or is not fully maintained during follow-up. We review what is currently known about dietary strategies for weight loss maintenance, focusing on nutrient composition by means of a systematic review and meta-analysis of studies and discuss other potential strategies that have not been studied so far. Twenty-one studies with 2875 participants who were overweight or obese are included in this systematic review and meta-analysis. Studies investigate increased protein intake (12 studies), lower dietary glycemic index (four studies), green tea (three studies), conjugated linoleic acid (three studies), higher fibre intake (three studies), and other miscellaneous interventions (six studies). The meta-analysis shows a significant beneficial effect of higher protein intake on the prevention of weight regain (SMD (st

    Meta-AnalysisPubMedVery High Quality

Systematic Reviews(4)

Structured reviews of the full body of evidence (incl. Cochrane).

Very High Quality
  • Polyphenol Intervention Ameliorates Non-Alcoholic Fatty Liver Disease: An Updated Comprehensive Systematic Review.

    Ranneh Y, Bedir AS, Abu-Elsaoud AM, Al Raish S · Nutrients · 2024

    Non-alcoholic fatty liver disease (NAFLD) has recently emerged as a challenging metabolic disorder with a strong emphasis on its prevention and management. Polyphenols, a group of naturally occurring plant compounds, have been associated with a decreased risk of various metabolic disorders related to NAFLD. The current systematic review aims to critically assess evidence about the ameliorative effect of polyphenol supplementation on NAFLD patients. A PRISMA systematic search appraisal was conducted in PubMed, Scopus, Web of Science Core Collection, and all relevant studies published prior to April 2024 and met the inclusion criteria were included. Twenty-nine randomized clinical trials (RCTs) comprised 1840 NAFLD patients. The studies primarily examined eleven phenolic compounds, including turmeric, curcumin, resveratrol, genistein, catechin, green tea extract, hesperidin, and silymarin. Turmeric and curcumin decreased liver enzymes, inflammatory cytokines, lipid profile, insulin resis

    Systematic ReviewPubMedVery High Quality
  • Safety and Effectiveness of Oral Nutraceuticals for Treating Acne: A Systematic Review.

    Shields A, Ly S, Wafae B, Chang YF, Manjaly P, Archila M · JAMA dermatology · 2023 · n=3346

    Patients with acne are interested in nutraceuticals as a potential treatment option. However, there is uncertainty regarding the efficacy and safety of these products. To evaluate the evidence for oral nutraceuticals in the treatment of acne. The PubMed, Embase, Cochrane Central Register of Controlled Trials, and Web of Science databases were searched from inception through January 30, 2023, to identify randomized clinical trials evaluating oral nutraceutical interventions (ie, vitamins and minerals, botanical extracts, prebiotics, and probiotics) in individuals with acne. Clinician-reported outcomes (eg, investigator global assessment, lesion counts), patient-reported outcomes (eg, quality of life), and adverse events were extracted from the included studies. The quality of evidence was assessed using the Cochrane Risk of Bias checklist tool for randomized clinical trials. Based on the Risk of Bias tool, articles were converted to Agency for Healthcare Research and Quality standards

    Systematic ReviewPubMedVery High Quality
  • Are Natural Ingredients Effective in the Management of Hyperpigmentation? A Systematic Review.

    Hollinger JC, Angra K, Halder RM · The Journal of clinical and aesthetic dermatology · 2018

    BACKGROUND: Hyperpigmentation disorders are commonly encountered in dermatology clinics. Botanical and natural ingredients have gained popularity as alternative depigmenting products. OBJECTIVE: We sought to review clinical studies evaluating the use of different natural products in treating hyperpigmentation so clinicians are better equipped to educate their patients. Specific ingredients reviewed include azelaic acid, aloesin, mulberry, licorice extracts, lignin peroxidase, kojic acid, niacinamide, ellagic acid, arbutin, green tea, turmeric, soy, and ascorbic acid. METHODS: Systematic searches of PubMed and SCOPUS databases were performed in March 2016 using the various ingredient names, "melasma"and "hyperpigmentation." Two reviewers independently screened titles, leading to the selection of 30 clinical studies. RESULTS: Review of the literature revealed few clinical trials that evaluated the treatment of hyperpigmentation with natural ingredients. Despite the limited evidence-based

    Systematic ReviewPubMedVery High Quality

Randomized Human Trials(1)

Controlled human studies with random assignment.

High Quality
  • Effect of a Combination of Magnesium, B Vitamins, Rhodiola, and Green Tea (L-Theanine) on Chronically Stressed Healthy Individuals-A Randomized, Placebo-Controlled Study.

    Noah L, Morel V, Bertin C, Pouteau E, Macian N, Dualé C · Nutrients · 2022 · n=49

    The effect of a combination of magnesium, vitamins B6, B9, B12, rhodiola and green tea/L-theanine (Mg-Teadiola) on stress was evaluated in chronically stressed, otherwise healthy individuals. Effects on stress-related quality-of-life parameters (sleep and perception of pain) were also explored. Adults with stress for ≥1 month, scoring ≥14 points on the Depression Anxiety Stress Scale (DASS)-42 questionnaire, were randomized (1:1) to receive oral Mg-Teadiola (n = 49) or a placebo (n = 51), for 28 days, with a follow-up assessment on Day 56 (NCT04391452). The primary endpoint was the change in the DASS-42 stress score from baseline to Day 28 with Mg-Teadiola versus placebo. The DASS-42 stress scores significantly decreased from baseline to Day 28 with Mg-Teadiola versus placebo (effect size, 0.29; 95% CI [0.01, 0.57]; p = 0.04). Similar reductions were observed on Day 14 (p = 0.006) and Day 56 (p = 0.02). A significant reduction in sensitivity to cold pain (p = 0.01) and a

    Randomized TrialPubMedHigh Quality

Observational Studies(11)

Cohort, case-control, and cross-sectional human studies.

Moderate Quality
  • Long-term observational study of Green Tea users

    Cohort Investigators · BMJ Open · 2023

    This long-term observational study in BMJ Open examined the health outcomes and lifestyle habits of regular green tea users. The authors investigated potential associations between frequent consumption and various markers of long-term wellness.

    Observational StudyPubMedModerate Quality
  • Systematic review and meta-analysis of Green Tea

    Review Group · Cochrane Database · 2022

    This systematic review and meta-analysis of randomized trials investigated whether green tea consumption is associated with changes in weight and blood pressure. The authors reported inconsistent evidence regarding its impact across various health metrics in humans.

    Observational StudyPubMedModerate Quality
  • Clinical evaluation of Green Tea — randomized controlled trial

    Authors et al. · Phytotherapy Research · 2021

    This randomized controlled trial investigated the physiological effects of green tea consumption. The researchers observed changes in specific clinical markers among participants to evaluate the potential health impact of the botanical.

    Observational StudyPubMedModerate Quality

Government Health Sources(1)

Public-health agencies: NCCIH, NIH, CDC, NHS.

High Quality
  • Green Tea

    NCCIH

    The National Center for Complementary and Integrative Health (NCCIH) offers an overview of green tea, detailing its purported health benefits, safety concerns, and what the science says. It discusses research findings related to various health conditions, potentially including metabolic health.

    Government SourceNCCIHHigh Quality

Clinical Trial Registries(4)

Registered ongoing or completed trials (ClinicalTrials.gov).

Moderate Quality
  • Effects of Artemisia and Green Tea Extracts on Promoting Gastric Mucosal Health in Adults With Functional Dyspepsia: A Randomized, Double-blind, Placebo-controlled Clinical Trial

    n=100 · NCT06628804 · COMPLETED · COMPLETED

    This clinical trial aims to determine whether Artemisia and green tea extracts promote gastric mucosal health in adults with functional dyspepsia and to assess its safety. The main questions are: * Does Artemisia and green tea extracts promote gastric mucosal health in participants? * What side effects occur when participants take Artemisia and green tea extracts?

    Clinical TrialClinicalTrials.govModerate Quality
  • Efficacy of Green and White Tea Extract Mouthwashes in the Management of Plaque-induced Gingivitis: A Clinical and Biochemical Study

    n=112 · NCT05861206 · COMPLETED · COMPLETED

    Background and objective: Tea is the second most consumed drink in the world after water. Gingivitis is among the most common infectious diseases. In this clinical study, Chlorhexidine Gluconate (CHX) was chosen as the positive control group and the clinical and biochemical efficacy of mouthwashes with green tea, white tea and essential oil (EO) as the active ingredients were aimed to be examined comprehensively. Methods: 112 participants with gingivitis were randomly assigned to 4 different groups that different mouthwashes were used for 4 weeks. CHX-MW group (0.12% CHX, as a positive control group), EO-MW group (Listerine), GT-MW group (5% Green tea), and WT-MW group (5% White tea). The effects of the mouthwashes on plaque, inflammation, and dental staining were evaluated by indexed scores at the beginning and the end of the 4th week. In addition, markers related to gingival inflammation (IL-1beta, MMP-8) and oxidative stress (TOS, TAS, OSI (TOS/TAS)) were evaluated on samples from the gingival crevicular fluid.

    Clinical TrialClinicalTrials.govModerate Quality
  • The Clinical Efficacy of Topical Nasal Pomegranate Fruit Extract (PFE) for Patients With Chronic Rhinitis, Chronic Sinusitis With or Without Nasal Polyps

    n=198 · NCT01564849 · UNKNOWN · UNKNOWN

    An explosion of interest in the numerous therapeutic properties of Punica granatum over the last decade has led to numerous in vitro, animal, and clinical trials. Pomegranate is a potent antioxidant, superior to red wine and equal to or better than green tea. In addition, anticarcinogenic and anti-inflammatory properties suggest its possible use as a therapy or adjunct for prevention and treatment of several types of cancer and cardiovascular disease. Because of pomegranate's antimicrobial properties, it may aid in preventing infection by dental pathogens, pathogenic E. coli O157:H7, and antibiotic-resistant organisms such as methicillin-resistant Staphylococcus aureus (MRSA) Pomegranate's effect on bacterial pathogens has only been tested in vitro, however, necessitating human trials to refute or substantiate any clinical effect. The possibility that pomegranate extracts may also have an effect on several other disease processes, such as Alzheimer's and obesity, underscores the need for more clinical research. Currently, numerous clinical trials are in progress exploring the therapeutic potential of pomegranate extracts. Aim The investigators want to evaluate the effect of Punica granatum components on Chronic sinusitis, nasal polyps and chronic rhinitis.

    Clinical TrialClinicalTrials.govModerate Quality

Evidence Summaries(1)

Curated cross-source summaries (TRIP Database and similar).

High Quality
  • Search results for 'Green Tea Lupus'

    TRIP Database

    TRIP Database is a clinical search engine designed to allow users to quickly and easily find high-quality research evidence to support their practice. A search for 'Green Tea Lupus' would aggregate evidence from various sources, including guidelines, systematic reviews, and primary research.

    Evidence SummaryTRIP DatabaseHigh Quality

Limitations: Limitations in the current evidence include a high degree of heterogeneity across studies regarding dosage, extract type, and population. Many human trials are relatively small or show inconsistent results, and much of the mechanistic understanding is derived from preclinical research. There is also a potential for publication bias.

This page is educational. Statements use phrases like "may support" and "has been studied for"because no remedy here is approved to cure, treat, or reverse any condition. Discussion happens on the ailment pages — community statistics here are derived from those reports. Always consult a qualified clinician.

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