Green tea extract is a concentrated form of green tea (Camellia sinensis). Its main active compounds are catechins, chiefly EGCG (epigallocatechin gallate), plus caffeine. It is sold mostly in weight-loss supplements and is also promoted for cholesterol and preventing heart disease and cancer.
Also known as: EGCG, epigallocatechin gallate, green tea catechins, Camellia sinensis.
Green tea extract has no intake value or upper limit. ODS says a brewed cup of green tea has about 240 to 320 mg of catechins and 45 mg of caffeine; weight-loss trials in a Cochrane review used 141 to 1,207 mg of catechins a day for 12 to 13 weeks. These are study protocols, not a recommendation.
It is sold in the US as a dietary supplement. Under the 1994 dietary supplement law (DSHEA), FDA does not approve dietary supplements before they are marketed, and the maker, not FDA, is responsible for safety and labeling. NCCIH notes that FDA has approved a prescription ointment made from a specific green tea extract for genital warts; that is a different product from extract pills.
On weight, ODS says a Cochrane review of 14 trials found green tea preparations reduced weight by about 0.95 kg more than placebo, but there was no significant difference in trials done outside Japan; catechins without caffeine did not seem to affect weight, and ODS concludes any effect is small and not likely to matter clinically. NCCIH says green tea lowered total and LDL cholesterol to a small extent in trials, mostly of extract supplements.
Liver injury is the main risk. NCCIH says liver injury, though uncommon, has been reported mostly with green tea extract tablets or capsules, and people with a specific immune gene variant (5% to 15% of Americans) appear more susceptible. ODS describes at least 50 case reports since 2006, a 2008 US Pharmacopeia review of 34 of those cases that judged green tea products probably caused 7 and possibly caused 27, and a 12-month trial in which extract with 843 mg of EGCG a day raised liver enzymes. USP advises taking extracts with food. Other side effects include nausea, constipation, stomach discomfort and higher blood pressure. Interactions, per NCCIH: green tea can lower blood levels of the beta-blocker nadolol and the statin atorvastatin, and interacted with raloxifene in a study. It contains caffeine, which matters in pregnancy.
We could not find a single published half-life or time to peak for green tea extract that applies to a supplement dose, so we do not list one. Extracts range from lightly processed leaf to concentrated EGCG, so no single figure would describe them (ODS).
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