Overview
Catechins, particularly epigallocatechin gallate (EGCG), are bioactive flavonoids found predominantly in green tea and are known for their antioxidant, anti-inflammatory, and cardiometabolic protective properties. Clinical evidence suggests that green tea catechins can accumulate in low-density lipoprotein (LDL) particles and protect against LDL oxidation, a key step in atherosclerosis development [7]. While some studies show modest improvements in endothelial function—such as increased flow-mediated dilation after acute EGCG supplementation in coronary artery disease patients [8]—results on systemic inflammation markers like C-reactive protein (CRP) are inconsistent, with meta-analyses showing no significant reduction [1]. Preclinical and emerging clinical data support a role for EGCG in metabolic syndrome, including potential benefits in insulin sensitivity and lipid metabolism, though long-term human trials show limited effects on adiposity or bone density [3][4]. Bioavailability of catechins is moderate and time-dependent, with peak plasma concentrations observed within 1–2 hours post-consumption [5].
Dosage Guide
Therapeutic Doses
For treatment of specific conditions
Upper Intake Limit
Maximum safe daily intake
800 mg— Upper limit for EGCG from supplements; higher doses linked to hepatotoxicity risk
Special Forms
Alternative forms for specific needs
For individuals sensitive to caffeine, used in long-term trials
Standardized high-dose supplementation for research and therapeutic use
Clinical Notes
- High-dose EGCG supplements (≥800 mg/day) have been associated with hepatotoxicity; liver function monitoring is advised.
- Take with food to reduce gastrointestinal irritation.
- Avoid on an empty stomach due to potential for nausea or liver enzyme elevations.
- Caffeine content in non-decaffeinated extracts may affect sensitive individuals.
- Drug interactions possible with stimulants, anticoagulants, and chemotherapy agents; consult healthcare provider.
Research
Meta-analysis of RCTs shows no significant effect of green tea catechins on plasma CRP levels.
Review highlights EGCG's potential therapeutic effects in metabolic syndrome beyond antioxidant and anti-inflammatory actions.
High-dose green tea extract (843 mg EGCG) did not significantly improve serum lipids in postmenopausal women over 12 months.
Long-term decaffeinated green tea extract supplementation did not alter adiposity or bone mineral density in overweight/obese postmenopausal women.
Green tea extract increases plasma catechin levels and antioxidant capacity within hours of ingestion.
Green tea polyphenols, especially EGCG, show chemopreventive potential in prostate cancer, though clinical evidence is limited.
Green tea catechins incorporate into LDL particles and prevent oxidation in humans after acute supplementation.
Acute EGCG supplementation (300 mg) improves endothelial function in patients with coronary artery disease.
