The principal catechin of green tea, purified and concentrated into capsules at levels far above what tea drinking delivers. It is chemically distinct from a whole green tea extract, which contains a mixture of catechins, caffeine and theanine.
EGCG is the compound behind most of green tea's laboratory reputation, and isolating it turns a beverage constituent into something that behaves more like a drug — including in its capacity for harm. Concentrated catechin extracts are now among the most frequently implicated agents in herbal and dietary supplement liver injury in the United States, and the European Food Safety Authority concluded that doses at and above 800 mg of EGCG per day taken as a supplement are associated with signs of liver damage. Against that sits a modest efficacy record: meta-analyses of green tea catechins for weight loss find effects of roughly a kilogram, often not sustained, and cardiovascular biomarker changes that are small. The risk-benefit arithmetic for a purified isolate is genuinely different from that for drinking tea.
Milligrams of EGCG; a "green tea extract" label may specify total polyphenols, total catechins or EGCG, and these are not interchangeable — a product without this marker may not resemble what was studied.
Also known as
Epigallocatechin gallate, EGCG, Green tea catechin isolate
Regulation: Sold as a dietary supplement in the US with no pre-market efficacy or safety review. The European Food Safety Authority identified 800 mg of EGCG daily from supplements as the level at which liver enzyme elevations appear, and several European countries have introduced labelling requirements or restrictions. Health Canada and the US Pharmacopeia have issued liver-injury warnings.
What the research used
The amounts, forms and durations published trials of EGCG isolate actually administered.
These are the amounts published trials administered — not a recommendation, and not a dose to copy. Trial participants were screened, supervised and given a characterised preparation. What is in a retail bottle is frequently not what was studied, and the amount that suits one person is not general advice.
Studied for Body weight and body composition trials
250–1200 mg
Limited
Catechin extract, daily, often with caffeine · 8–24 weeks
Most weight-loss trials used extracts containing caffeine, which confounds attribution. Pooled weight differences are around one kilogram and frequently disappear in longer trials.
Small reductions in LDL cholesterol are reported across meta-analyses. The upper end of this range sits at the level European regulators associate with liver enzyme elevations.
This is general information about food, not medical advice. It cannot diagnose, treat or replace guidance from a clinician who knows your history.
When it was taken
Each window says whether a trial compared it against an alternative, or whether it is convention and pharmacology. Most timing advice is the second kind.
Each timing below was actually compared against an alternative in a trial, which is unusual.
🍽️With food
Moderate
Taking catechin extracts with food lowers peak plasma concentration but is the safer pattern, because the documented liver injury cases cluster around fasted high-dose use. Absorption studies show fasted dosing produces considerably higher peaks, which is the opposite of what you want here.
Timing was tested. A trial compared this window against another and reported a difference.
The evidence in depth
Best supported: Limited
What each association actually rests on, and the papers behind it. A rating describes the state of the research, not how promising the supplement sounds. How we rate evidence.
Pooled trials show small reductions in total and LDL cholesterol with catechin supplementation. The absolute changes are modest and the trials are short.
Limited evidence. Early human work, or mostly lab and animal research.
Meta-analyses of green tea catechins report a small average weight reduction, typically under a kilogram and a half, with results heavily influenced by whether caffeine was included and by ethnicity of the study population. Longer trials tend toward null.
What may be going on: Catechins inhibit catechol-O-methyltransferase, prolonging noradrenaline signalling and modestly raising energy expenditure, an effect that overlaps with and depends partly on caffeine.
Limited evidence. Early human work, or mostly lab and animal research.
Catechin intake raises plasma antioxidant capacity and alters markers of oxidative damage in short human studies. These are surrogate measures whose clinical meaning is unclear.
Limited evidence. Early human work, or mostly lab and animal research.
Randomised controlled trial · Nutrition research (New York, N.Y.) · 2016 · PMID 26773777
Deep research mode adds each paper’s own conclusion and stated limitations.
Things to know
Interactions, contraindications and dose limits, most serious first. Concentrated extracts interact with medication in ways the whole plant does not, so this section carries more weight here than it does on a food page.
Worth knowing
Liver injury is the defining risk
Concentrated green tea catechin extracts are among the most common causes of supplement-associated liver injury recorded by the US Drug-Induced Liver Injury Network, with cases ranging from asymptomatic enzyme elevations to acute liver failure requiring transplant. Risk rises with dose, with fasted administration, and in people carrying a particular HLA variant. Anyone taking an EGCG isolate who develops fatigue, nausea, dark urine or yellowing of the eyes should stop and seek medical assessment the same day.
Too much
The 800 mg threshold
European regulators concluded that 800 mg of EGCG daily from a supplement is the level at which liver enzyme elevations become apparent in trials. Many retail products contain that much or more in a daily serving, and stacking several green tea products makes it easy to exceed without noticing.
Interaction
Reduces absorption of several drugs and of iron
Interacts withNadolol, non-heme iron, warfarin, some statins
Catechins bind non-heme iron and reduce its absorption substantially, which matters for anyone with low iron status. Green tea catechins also lower plasma levels of nadolol and interact with several other medicines through transporter inhibition.
Worth knowing
Caffeine content varies and is often unlabelled
Non-decaffeinated catechin extracts carry meaningful caffeine, which is frequently not stated clearly. In products marketed for weight loss this is often where the perceived effect comes from.
Avoid
Avoid with existing liver disease and in pregnancy
Concentrated catechin extracts are not appropriate for anyone with liver disease or on hepatotoxic medication. High-dose EGCG in pregnancy has also been questioned on folate-metabolism grounds and has not been established as safe.
In the food catalogue
The whole-food form, where one exists. The evidence for a concentrated extract rarely transfers to the food, or the other way round — these are cross-links, not equivalents.