Green Tea Extract
Research reviewed: up until 05/2023
Green Tea Extract (Camellia sinensis) is a dietary supplement with 21 published peer-reviewed studies involving 52,858 participants, researched for Obesity with metabolic syndrome, Mortality rate, Weight Management and 7 more areas.
Evidence at a Glance
Strength is scored by study design, sample size, study type, and outcomes
Obesity with metabolic syndrome
ModerateMortality rate
ModerateWeight Management
ModerateWeight Loss
ModerateCholesterol & Lipids
ModerateCognitive Function & Brain Health
ModerateLiver Health & NAFLD
ModerateBlood Pressure & Cardiovascular Health
ModerateAthletic Performance & Fat Oxidation
ModerateClinical trials
ModerateResearch Visualised
Visual breakdown of the clinical data.
Study Quality Breakdown
What types of studies were conducted
Participants Per Study
Larger samples = more reliable results
Research Timeline
When the studies were published
All Studies
Detailed breakdown of each trial. Click to expand.
Obesity with metabolic syndrome
To examine the effects of green tea extracts and beverages on body weight, fasting glucose, and lipids, and oxidative stress in obese subjects with metabolic syndrome (which is a medical term for a combination of diabetes, high blood pressure and obesity).
Study Type
Randomised, single-blind, controlled trial
Purpose
To examine the effects of green tea extracts and beverages on body weight, fasting glucose, and lipids, and oxidative stress in obese subjects with metabolic syndrome (which is a medical term for a combination of diabetes, high blood pressure and obesity).
Dose
870 mg/day of green tea capsules (2 x 435 mg capsules) or 928 mg/day of green tea beverages (4 cups x 232 mg tea bags)
Participants
35 obese males and females with metabolic syndrome and an average age of 43
Duration
8 weeks
Results
The researchers observed that the average body weight and body mass index (BMI) of obese participants in the green tea beverage and supplementation group significantly decreased after 8 weeks. A significant reduction in the biomarkers of oxidative stress (malondialdehyde and 4-hydroxynonenal) was also observed in green tea drinkers but not in the green tea supplementation group. A decrease in oxidative stress is associated with reduced risks of cardiovascular disease. The study also found that the green tea drinkers were associated with a decreasing trend in LDL-cholesterol and an increasing trend in HDL-cholesterol compared to the control groups. High levels of LDL-cholesterol, also known as “bad” cholesterol, are associated with a higher risk for heart disease and stroke. In contrast, higher levels of HDL-cholesterol is associated with a lower risk of heart disease and stroke.
Mortality rate
To investigate the associations between green tea consumption and mortality from all causes and specific causes.
Study Type
Prospective cohort study
Purpose
To investigate the associations between green tea consumption and mortality from all causes and specific causes.
Participants
40,530 participants from the Ohsaki National Health Insurance Cohort Study
Duration
11 years of follow-up for all-cause mortality and up to 7 years of follow-up for cause-specific mortality
Results
The study found an association between increased green tea consumption and lower deaths from all causes and cardiovascular disease, except cancer. The association with lower cardiovascular disease deaths was stronger than that with deaths from all causes. The association with deaths from all causes was stronger in women.
How They Measured It
The amount of green tea consumption was determined using a food frequency questionnaire. The causes of death were investigated by reviewing the death certificates filed at Ohsaki Public Health Center.
To investigate the association between green tea consumption and death from all causes, cancer, and cardiovascular disease among elderly people.
Study Type
Population-based, prospective cohort study
Purpose
To investigate the association between green tea consumption and death from all causes, cancer, and cardiovascular disease among elderly people.
Participants
12,251 men and women aged 65–84 years
Duration
6 years follow up from December 1999 to March 2006
Results
The study found that those who consumed seven or more cups of green tea per day were associated with a 55% lower risk of death from all causes and a 75% lower risk of death from cardiovascular disease when compared with those who consumed less than one cup per day. A moderate dose of green tea consumption was also associated with a lower risk of colorectal cancer mortality.
How They Measured It
The frequency of green tea consumption was determined using questionnaires. The causes of death of the deceased subjects were identified using the National Vital Statistics Database from the Ministry of Health, Labour and Welfare of Japan.
Weight Management
To evaluate therapeutic effect of high-dose green tea extract on weight reduction
Study Type
Randomized, double-blind, placebo-controlled clinical trial
Purpose
To evaluate therapeutic effect of high-dose green tea extract on weight reduction
Dose
856.8 mg EGCG daily (high-dose green tea extract)
Participants
Women with central obesity (mean age ~40)
Duration
12 weeks
Results
High-dose EGCG resulted in significant weight loss, decreased BMI, reduced waist circumference. Adiponectin increased and ghrelin decreased
How They Measured It
Body weight, BMI, waist circumference, adipokine levels (leptin, adiponectin), oxidative stress markers
To evaluate the combined effect of green tea catechins with or without caffeine on anthropometric measures and weight loss
Study Type
Systematic review and meta-analysis
Purpose
To evaluate the combined effect of green tea catechins with or without caffeine on anthropometric measures and weight loss
Dose
Green tea catechins (various doses)
Participants
Meta-analysis of randomized controlled trials
Duration
Various study periods
Results
Green tea catechins showed significant dose-dependent effects on weight and body composition, with benefits more pronounced in doses ≥300 mg EGCG daily.
How They Measured It
Body weight, BMI, body fat percentage, fat mass
To evaluate the combined effect of green tea extract and α-glucosyl hesperidin in preventing obesity
Study Type
Randomized, placebo-controlled trial
Purpose
To evaluate the combined effect of green tea extract and α-glucosyl hesperidin in preventing obesity
Dose
Green tea extract combined with α-glucosyl hesperidin
Participants
Individuals at risk for obesity
Duration
12 weeks
Results
Combined green tea and hesperidin supplementation significantly reduced body weight and improved metabolic parameters compared to placebo.
How They Measured It
Body weight, adiposity markers, metabolic parameters
Weight Loss
To evaluate therapeutic effect of high-dose green tea extract on weight reduction
Study Type
Randomised, double-blind, placebo-controlled trial
Purpose
To evaluate therapeutic effect of high-dose green tea extract on weight reduction
Dose
High-dose EGCG green tea extract
Participants
Obese women
Duration
12 weeks
Results
Significant weight loss from 76.8 ± 11.3 kg to 75.7 ± 11.5 kg (p = 0.025). Decreases in BMI (p = 0.018) and waist circumference (p = 0.023).
How They Measured It
Body weight, BMI, waist circumference, fat mass
To assess the effect of green tea extract on body composition in obese women
Study Type
Randomised, double-blind, placebo-controlled trial
Purpose
To assess the effect of green tea extract on body composition in obese women
Dose
Green tea extract
Participants
Obese women
Duration
12 weeks
Results
Green tea extract produced significant reductions in body weight and body fat compared to placebo.
How They Measured It
Body weight, body composition, anthropometric measures
Cholesterol & Lipids
To evaluate effects of green tea catechin on serum lipids in postmenopausal women
Study Type
Randomised, double-blind, placebo-controlled trial
Purpose
To evaluate effects of green tea catechin on serum lipids in postmenopausal women
Dose
~1315 mg green tea catechins (843 mg EGCG)
Participants
Postmenopausal women with elevated cholesterol
Duration
12 months
Results
Daily supplementation significantly reduced total cholesterol, LDL, and non-HDL cholesterol. Greatest effects in high cholesterol baseline group (-8.3% total, -12.2% LDL).
How They Measured It
Total cholesterol, LDL cholesterol, HDL cholesterol, triglycerides
To evaluate effects of green tea extract on insulin resistance and glucose control in type 2 diabetes
Study Type
Randomized, double-blind, placebo-controlled trial
Purpose
To evaluate effects of green tea extract on insulin resistance and glucose control in type 2 diabetes
Dose
Green tea extract (various doses)
Participants
Patients with type 2 diabetes and lipid abnormalities
Duration
8-16 weeks
Results
Green tea extract decreased triglycerides and HOMA-IR index, indicating improved insulin sensitivity in some studies, though effects on fasting glucose were inconsistent.
How They Measured It
Fasting glucose, HbA1c, HOMA-IR, serum lipids, GLP-1
Cognitive Function & Brain Health
To evaluate effects of heat-treated green tea extract on memory function and brain connectivity in individuals with subjective memory impairment
Study Type
Double-blind, randomized, placebo-controlled trial
Purpose
To evaluate effects of heat-treated green tea extract on memory function and brain connectivity in individuals with subjective memory impairment
Dose
Heat-treated green tea extract
Participants
Individuals with subjective memory impairment
Duration
12 weeks
Results
Heat-treated green tea extract group demonstrated significant improvements in memory function and increased functional connectivity within the right precuneus region of the default mode network compared to placebo.
How They Measured It
Memory function tests, default mode network functional connectivity (fMRI)
To evaluate the effects of green tea on cognition, mood, and human brain function
Study Type
Systematic review and meta-analysis
Purpose
To evaluate the effects of green tea on cognition, mood, and human brain function
Dose
Green tea consumption (various forms and doses)
Participants
Meta-analysis of multiple studies
Duration
Various study periods
Results
Green tea demonstrated beneficial effects on cognitive function and mood, with the combined influence of caffeine and L-theanine being particularly beneficial. Habitual green tea drinking decreased cognitive dysfunction.
How They Measured It
Cognitive performance, mood assessment, neuroimaging outcomes
To evaluate effects of daily green tea catechin intake on cognitive function in middle-aged and older subjects
Study Type
Randomized, placebo-controlled study
Purpose
To evaluate effects of daily green tea catechin intake on cognitive function in middle-aged and older subjects
Dose
Daily green tea catechins
Participants
Middle-aged and older adults
Duration
Multiple months
Results
Green tea catechin supplementation significantly improved cognitive function measures including working memory and attention compared to placebo.
How They Measured It
Cognitive assessment battery, working memory, attention
Liver Health & NAFLD
To evaluate effects of green tea extract with high-density catechins on liver function and fat infiltration in NAFLD patients
Study Type
Randomized, double-blind, placebo-controlled trial
Purpose
To evaluate effects of green tea extract with high-density catechins on liver function and fat infiltration in NAFLD patients
Dose
High-density green tea catechins
Participants
Patients with nonalcoholic fatty liver disease
Duration
12 weeks
Results
High-density green tea catechin group significantly decreased serum ALT levels, reduced liver fat content and inflammation by reducing oxidative stress.
How They Measured It
Liver enzymes (ALT, AST), liver fat content, inflammation markers, oxidative stress
To evaluate the effect of green tea extract supplementation on liver enzymes in NAFLD patients
Study Type
Randomized, placebo-controlled trial
Purpose
To evaluate the effect of green tea extract supplementation on liver enzymes in NAFLD patients
Dose
500 mg green tea extract daily
Participants
Patients with nonalcoholic fatty liver disease
Duration
90 days
Results
Green tea extract supplementation decreased liver enzymes in NAFLD patients and improved serum levels of liver function markers.
How They Measured It
Liver function tests (ALT, AST, ALP), liver ultrasound
To evaluate effects of green tea or green tea catechins on liver enzymes in healthy subjects and NAFLD patients
Study Type
Systematic review and meta-analysis
Purpose
To evaluate effects of green tea or green tea catechins on liver enzymes in healthy subjects and NAFLD patients
Dose
Green tea extract (various doses)
Participants
Meta-analysis of randomized clinical trials
Duration
Various study periods
Results
Subgroup analyses showed green tea significantly reduced liver enzyme levels in NAFLD patients, though overall effect was nonsignificant. A small increase was observed in healthy subjects.
How They Measured It
ALT, AST, ALP levels
Blood Pressure & Cardiovascular Health
To evaluate the effect of green tea supplementation on blood pressure in adults
Study Type
Systematic review and meta-analysis
Purpose
To evaluate the effect of green tea supplementation on blood pressure in adults
Dose
Green tea extract (various doses)
Participants
Meta-analysis of randomized controlled trials
Duration
Various study periods
Results
Green tea supplementation showed small reductions in blood pressure (both systolic and diastolic) compared to placebo, though clinical significance remains uncertain.
How They Measured It
Systolic and diastolic blood pressure changes
To evaluate green tea extract effects on blood pressure, inflammatory biomarkers, and oxidative stress in obese, hypertensive patients
Study Type
Randomized, placebo-controlled trial
Purpose
To evaluate green tea extract effects on blood pressure, inflammatory biomarkers, and oxidative stress in obese, hypertensive patients
Dose
Green tea extract supplementation
Participants
Obese patients with hypertension
Duration
3 months
Results
Green tea extract significantly reduced blood pressure and decreased serum TNF-α and C-reactive protein while increasing total antioxidant status. Markers of insulin resistance also improved.
How They Measured It
Blood pressure, inflammatory markers (TNF-α, CRP), total antioxidant status, insulin resistance parameters
Athletic Performance & Fat Oxidation
To evaluate the effect of green tea supplementation combined with exercise on weight loss and body composition
Study Type
Randomized, double-blind, placebo-controlled trial
Purpose
To evaluate the effect of green tea supplementation combined with exercise on weight loss and body composition
Dose
Green tea extract with catechins
Participants
Overweight/obese individuals
Duration
12 weeks
Results
Green tea catechins enhanced the weight-loss effect of exercise training compared to exercise alone or placebo.
How They Measured It
Body weight, fat mass, lean mass, exercise capacity
To evaluate the effect of green tea catechins on fat oxidation and exercise substrate utilization
Study Type
Randomized, double-blind, placebo-controlled trial
Purpose
To evaluate the effect of green tea catechins on fat oxidation and exercise substrate utilization
Dose
Green tea extract with catechins
Participants
Active individuals
Duration
Acute supplementation with exercise testing
Results
Green tea catechins significantly increased fat oxidation during exercise and improved metabolic flexibility between carbohydrate and fat utilization.
How They Measured It
Fat oxidation rates, carbohydrate oxidation, exercise performance
Clinical trials
To evaluate whether green tea extract standardized to 150 mg EGCG twice daily prevents colorectal adenomas over 3 years.
Study Type
Randomized, double-blind, placebo-controlled trial
Purpose
To evaluate whether green tea extract standardized to 150 mg EGCG twice daily prevents colorectal adenomas over 3 years.
Dose
150 mg EGCG twice daily (300 mg/day total) for up to 3 years
Participants
879 participants randomized (40 German centers; initially 1,001 with colon adenomas)
Duration
3 years
Results
Adenoma rate was 51.1% (GTE) vs 55.7% (placebo); 4.6% difference not statistically significant (P=0.1613). GTE was well tolerated with no major safety concerns.
How They Measured It
Adenoma/colorectal cancer presence at follow-up colonoscopy 3 years post-randomization (modified ITT and per-protocol)
Frequently Asked Questions
Common questions about Green Tea Extract research
There are currently 21 peer-reviewed studies on Green Tea Extract (Camellia sinensis), involving 52,858 total participants. Research covers Obesity with metabolic syndrome, Mortality rate. The overall evidence strength is rated as Strong.
The evidence is currently rated as "Strong Evidence". This rating is based on study design quality (randomisation, blinding, placebo controls), sample sizes, study types (17 human studies), and reported outcomes.
Green Tea Extract has been researched for: Obesity with metabolic syndrome, Mortality rate. Each area has its own body of evidence which you can explore in the study breakdowns above.
Yes, 17 out of 21 studies are human trials. Human trials carry more weight in our evidence scoring system.
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