Green tea extract (catechins / EGCG) — intervention evidence review

Regulatory status: dietary supplement

Mechanism evidence: human

• **Upper-respiratory infections / colds / influenza** (incidence, symptom days) — the 225 mg “immune support” claim.
• **Body weight and fat mass / fat oxidation** (kg lost, % fat, 24-h EE and fat oxidation).
• **LDL-cholesterol** (and total cholesterol) as a cardiometabolic surrogate.
• **Cancer prevention** (incident cancer, or progression of high-grade PIN / mammographic density).
• **Cognition** (memory, attention, MMSE, working memory) in healthy or cognitively impaired adults.

Green tea **as a beverage** is a different intervention from a concentrated extract. The extract has one clearly established human effect: a **hepatocellular liver-injury risk** that rises with EGCG dose, duration, bolus dosing, and **fasting**, is idiosyncratic at lower doses, and has been serious enough for EFSA, Health Canada, USP, and the European Commission to write warnings and (in the EU) a hard <800 mg EGCG/day cap. Against that, the benefit record at human doses is modest and outcome-specific: **LDL about −5 mg/dL** (real, small, surrogate); **weight about −0.6 to −1.3 kg** in optimistic pools and **−0.04 kg outside Japan**, with caffeine doing most of the thermogenic work and **300 mg/day caffeine-free EGCG failing**; **URTI/influenza meta-RRs ~0.67–0.79** that mix Japanese gargling, catechin drinks, and a proprietary EGCG+theanine capsule — not 225 mg unnamed extract; **cancer prevention unproven** (Cochrane; Bettuzzi unreplicated; MGTT density null at 843 mg EGCG); **cognition unsupported** as EGCG monotherapy (acute null, 12-month MMSE null, one 12-week working-memory signal).

Confidence: moderate