Overview

Epigallocatechin gallate (EGCG) is the most abundant and bioactive catechin found in green tea, responsible for many of green tea's health benefits. As a supplement, purified EGCG or green tea extract standardized for EGCG content is marketed for fat loss, antioxidant support, cardiovascular health, and cancer prevention.

Critical safety concern: High-dose EGCG supplements (particularly fasted) have been linked to liver toxicity in some individuals. Doses above 800 mg daily from supplements require caution, with lower risk when consumed with food or as part of whole green tea.

Primary applications focus on fat oxidation support (though weight loss effects are modest), antioxidant and anti-inflammatory effects, cardiovascular health (cholesterol, blood pressure), cancer prevention research (observational and preclinical), and metabolic health support.

Evidence quality is moderate for metabolic health and cardiovascular benefits, preliminary for cancer prevention in humans, with extensive preclinical research but translation to clinical outcomes requiring more study.

Safety is generally good at moderate doses (300-400 mg daily) with food, but concerns exist at high doses (above 800 mg daily) particularly on empty stomach.

Mechanisms, Evidence, and Safety Considerations

Fat Loss: Minimal Effects

Antioxidant activity is EGCG's most fundamental property - strong free radical scavenging, inhibition of oxidative stress, and support of endogenous antioxidant enzymes. This underlies many downstream effects.

Fat oxidation enhancement occurs through multiple pathways: inhibition of catechol-O-methyltransferase (COMT, which degrades catecholamines like epinephrine involved in fat breakdown), thermogenesis increase, and direct effects on adipocyte metabolism.

For weight loss, meta-analyses show EGCG (typically 300-600 mg daily combined with caffeine) produces modest weight loss of 0.5-1.5 kg over 12 weeks compared to placebo. Effects are small and not meaningful for most individuals. EGCG + caffeine combination is more effective than EGCG alone.

For cardiovascular health, research shows EGCG (250-500 mg daily) modestly reduces LDL cholesterol and blood pressure, improves endothelial function, and has anti-inflammatory effects. Benefits are modest but consistent.

Dosing and Critical Safety

For cancer prevention, extensive preclinical research shows anticancer effects in lab and animal models. Epidemiological studies link green tea consumption to reduced cancer risk (breast, prostate, colorectal). However, human intervention trials are limited and mixed. EGCG shows promise but isn't proven cancer prevention in humans.

For metabolic health, EGCG improves insulin sensitivity and glucose metabolism in some studies, with potential benefits for metabolic syndrome and type 2 diabetes prevention.

Dosing: 300-400 mg daily for general antioxidant and cardiovascular support. 400-600 mg daily (with caffeine 100-200 mg) for metabolic support or modest fat oxidation effects. Avoid exceeding 800 mg daily from supplements due to liver toxicity concerns.

Take with food to improve tolerability and reduce liver toxicity risk. Green tea (3-5 cups daily providing 200-400 mg EGCG) is safer long-term than high-dose isolated supplements.

Liver Toxicity Warning

Liver toxicity concerns: Case reports and studies link high-dose EGCG supplements (typically above 800 mg daily, especially fasted) to hepatotoxicity (elevated liver enzymes, hepatitis, rare liver failure). Risk factors: fasted consumption, high doses, individual susceptibility, and potentially genetic variations affecting EGCG metabolism.

European Food Safety Authority (EFSA) set 800 mg daily as upper safe limit for EGCG from supplements. Consuming EGCG with food and staying below this threshold minimizes risk. Green tea beverage consumption (even at high intakes) hasn't shown liver toxicity, suggesting isolated supplements pose higher risk.

Those with liver disease or taking hepatotoxic medications should avoid high-dose EGCG supplements or use only under medical supervision.

Other side effects: nausea or stomach upset (particularly on empty stomach), headache, iron absorption interference (EGCG chelates iron - separate from iron supplements/high-iron meals by 2+ hours), and rare: dizziness, insomnia from caffeine content if using green tea extract.

Drug interactions: anticoagulants (EGCG has anti-platelet effects), blood pressure medications (additive effects), chemotherapy drugs (interactions vary - consult oncologist), and iron supplements (reduced absorption).

EGCG shows promise for cardiovascular and metabolic health with good antioxidant research but requires caution regarding liver toxicity at high supplement doses, with moderate consumption or whole green tea being safer long-term approaches.

References

Hu J, Webster D, Cao J, Shao A. The safety of green tea and green tea extract consumption in adults - Results of a systematic review. Regul Toxicol Pharmacol. 2018;95:412-433.

Jurgens TM, Whelan AM, Killian L, Doucette S, Kirk S, Foy E. Green tea for weight loss and weight maintenance in overweight or obese adults. Cochrane Database Syst Rev. 2012;12:CD008650.