Catechins & EGCG: Green Tea Polyphenols Explained

Catechins are a type of flavanol found primarily in tea, with green tea containing the highest concentrations. Epigallocatechin gallate (EGCG) is the most abundant and most studied catechin in green tea, accounting for 50-80% of total catechin content in a typical cup.

How EGCG Works

EGCG has a remarkably broad set of biological activities. It inhibits catechol-O-methyltransferase (COMT), an enzyme involved in catecholamine metabolism, which may partly explain green tea's mild thermogenic and alertness effects. EGCG also modulates multiple signaling pathways (AMPK, mTOR, NF-kB) and has been studied for metabolic, cardiovascular, and neuroprotective effects.

In green tea, EGCG works alongside L-theanine, the calming amino acid that modulates the stimulant effects of caffeine. This combination may explain why green tea is often described as producing "calm alertness" compared to coffee.

Bioavailability & Cautions

EGCG is poorly absorbed (oral bioavailability under 5%) and rapidly metabolized. Taking EGCG on an empty stomach improves absorption but can cause nausea. High-dose green tea extract supplements have been associated with rare but serious liver toxicity in case reports, particularly on an empty stomach.

Food Sources

Matcha provides the highest catechin dose because the whole leaf is consumed. Brewed green tea (especially first-flush, shade-grown varieties) is the standard source. White tea, oolong, and even black tea contain catechins in decreasing amounts due to oxidation during processing.