The green tea compound EGCG slows down a body enzyme that normally breaks down adrenaline, so your adrenaline sticks around longer and might keep you feeling more alert.
Evidence from Studies
Supporting (2)
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Enzymology of methylation of tea catechins and inhibition of catechol-O-methyltransferase by (-)-epigallocatechin gallate.
The study found that a compound in green tea (EGCG) blocks an enzyme (COMT) that normally breaks down adrenaline (epinephrine). If the enzyme is blocked, adrenaline lasts longer in the body — which is exactly what the claim says.
Molecular modelling study of the mechanism of high-potency inhibition of human catechol-O-methyltransferase by (–)-epigallocatechin-3-O-gallate
This study found that a compound in green tea (EGCG) sticks tightly to a body enzyme that normally breaks down adrenaline (epinephrine), which means adrenaline stays active longer — exactly what the claim says.
Contradicting (1)
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Efficacy of a green tea extract rich in catechin polyphenols and caffeine in increasing 24-h energy expenditure and fat oxidation in humans.
The study found that green tea makes your body burn more energy and increases a stress hormone called norepinephrine, but it didn’t check if EGCG blocks the enzyme that breaks down epinephrine — so we can’t say if the claim about slowing epinephrine breakdown is true.
Gold Standard Evidence Needed
According to GRADE and EBM methodology, here is what ideal scientific evidence would look like to definitively prove or disprove this specific claim, ordered from strongest to weakest evidence.