Green Tea Extract
Green Tea Extract (EGCG)
Green tea extract (GTE) is a concentrated polyphenol supplement derived from Camellia sinensis leaves, standardized primarily for its catechin content, especially epigallocatechin gallate (EGCG). It is widely used for antioxidant support, metabolic enhancement, fat oxidation, cognitive function, and cardiovascular health. Research also supports its role in insulin sensitivity improvement and neuroprotection.
Mechanism of Action
EGCG inhibits catechol-O-methyltransferase (COMT), an enzyme that degrades catecholamines like norepinephrine, thereby prolonging sympathetic nervous system activation and increasing thermogenesis and fat oxidation. It also acts as a potent antioxidant by scavenging reactive oxygen species and upregulating Nrf2-mediated antioxidant pathways. Additionally, EGCG modulates AMPK signaling, influences lipid metabolism, and inhibits inflammatory NF-κB pathways, contributing to its broad metabolic and cytoprotective effects.
Evidence by Health Goal(18 goals)
Dosing Protocols
Between meals or 1-2 hours before exercise; avoid taking on an empty stomach if sensitive
Cycle: 8-12 weeks on, 4 weeks off recommended to reduce hepatotoxicity risk
Ensure product is standardized to at least 45-50% EGCG by weight. Doses above 800mg/day of EGCG significantly increase hepatotoxicity risk. Decaffeinated extracts preferred for those sensitive to caffeine. Total polyphenol intake from all sources should be considered.
Safety & Side Effects
Green tea extract is generally safe at evidence-based doses (400-800mg EGCG/day) for healthy adults, but there are documented cases of drug-induced liver injury (DILI) at higher doses or with concentrated supplements taken on an empty stomach; routine monitoring of liver enzymes is advisable with long-term use. Individuals with liver conditions, anemia, cardiovascular disease, or those who are pregnant or breastfeeding should consult a healthcare provider before use.
Possible Side Effects
- !Nausea and gastrointestinal discomfort, especially on an empty stomach
- !Caffeine-related effects (jitteriness, insomnia, elevated heart rate) if non-decaffeinated extract is used
- !Headache, particularly during early use or at higher doses
- !Reduced non-heme iron absorption with concurrent meal consumption
- !Elevated liver enzymes (hepatotoxicity) at high doses exceeding 800mg EGCG/day or with prolonged use
- !Dizziness or lightheadedness, particularly in those with lower blood pressure
- !Rare allergic reactions including skin rash or itching
Interactions
- -May enhance anticoagulant effects of warfarin and other blood thinners, increasing bleeding risk
- -Can potentiate stimulant and thermogenic effects of caffeine, synephrine, or other sympathomimetics
- -May reduce absorption and efficacy of certain medications including statins, beta-blockers, and nadolol due to inhibition of intestinal transport proteins (OATP1A2)
- -Inhibits non-heme iron absorption — avoid co-administration with iron supplements or iron-rich meals in iron-deficient individuals
- -May have additive blood pressure-lowering effects when combined with antihypertensive medications, risking hypotension
Cost & Where to Buy
Cost varies significantly by EGCG standardization percentage, brand quality, and whether the extract is decaffeinated. Budget brands with lower standardization are cheaper; pharmaceutical-grade or third-party tested products with 50%+ EGCG cost more. Bulk powder purchases can reduce cost substantially.
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