Green Tea Extract – EGCG, Antioxidants and Fat Metabolism

Green Tea Extract (GTE) is a highly concentrated plant extract derived from the leaves of Camellia sinensis. It contains a complex profile of polyphenols, particularly catechins – led by EGCG (Epigallocatechin gallate), the most active and well-researched compound.

Active Compound Profile of Catechins

Catechin	Abbreviation	Proportion in Green Tea	Effect
Epigallocatechin gallate	EGCG	50–80% of catechins	Strongest antioxidant; main active ingredient
Epigallocatechin	EGC	~15%	Antioxidant, anti-inflammatory
Epicatechin gallate	ECG	~10%	Antioxidant
Epicatechin	EC	~5%	Cardioprotective, NO synthesis

Mechanisms of Action of EGCG

COMT Inhibition: EGCG inhibits catechol-O-methyltransferase, which breaks down noradrenaline → prolonged sympathoadrenergic activation → thermogenic effect and lipolysis
Fat Oxidation: Increases fatty acid oxidation through synergy with caffeine (both together > than individually)
Antioxidant: Neutralizes free radicals, activates NRF2 pathway
Anti-inflammatory: Inhibits NF-κB pathway
Neuroprotection: Protects neurons from oxidative stress; inhibits beta-amyloid aggregation
Blood Glucose Control: Improves insulin sensitivity, inhibits alpha-glucosidase

Documented Effects with Dosage

Effect	Dose (EGCG)	Evidence
Thermogenesis (+4–5% energy expenditure)	270–600 mg EGCG/day	Good (several RCTs)
Fat oxidation (especially with caffeine)	300–500 mg EGCG + caffeine	Very well-documented
Glucose control	400–800 mg EGCG	Moderate
Cardiovascular markers	200–400 mg EGCG	Good (LDL reduction)
Cognition	400 mg GTE + L-Theanine	Moderate

Caffeine Synergism

Caffeine + EGCG is one of the best-documented combinations in sports nutrition for fat burning. Caffeine increases lipolysis (fat mobilization), EGCG inhibits the breakdown of stimulating noradrenaline → both potentiate each other.

Dosage and Precautions

Recommended Dose: 400–800 mg standardized extract (45–50% EGCG) daily. Take with meals for better tolerability.

Caution with High Doses: Liver damage has been reported in rare cases from 800 mg EGCG/day (on an empty stomach). The EFSA has set an upper safe limit of 800 mg EGCG/day (supplementary). Do not take high doses on an empty stomach.

Interactions: Reduces iron absorption (take iron-containing supplements/meals at a different time). May potentiate blood pressure-lowering medication.

Frequently Asked Questions (FAQ)

How many cups of green tea correspond to the extract?

One cup of green tea contains ~50–100 mg EGCG. So, 400 mg EGCG would be equivalent to 4–8 cups daily. Supplements allow for therapeutic doses without the amount of caffeine found in tea.

Green tea extract for weight loss – realistic expectations?

Meta-analyses show an average weight loss of ~1.3 kg over 12 weeks vs. placebo – modest but measurable. GTE does not replace a caloric deficit but can support it.