EGCG (ekstrakt z zielonej herbaty): metabolizm i antyoksydanty (tabela)
EGCG and green tea extract in studies: metabolism, heart, liver, and drug interactions. EFSA warns against 800 mg daily and does not recommend this dose.
Epigallocatechin gallate, abbreviated as EGCG, is the most active catechin in green tea. One number has grown around it, which is worth reversing right at the beginning. In Polish and foreign descriptions of supplements, the statement is repeated that EFSA considered 800 mg of EGCG daily to be a safe dose. The EFSA opinion from 2018 states the opposite: it is precisely from 800 mg daily from a dietary supplement that interventional studies showed a statistically significant increase in serum aminotransferase activity (EFSA, EFSA Journal, 2018). This one reversed number is not an exception, as a similarly reversed statement about the absorption of catechins with meals is often found. This article therefore collects what has actually been measured about EGCG: how much is provided by infusion, how much by capsule, the size of the metabolic effect, what studies have shown regarding the heart and cancer, and which interactions can nullify the effect of prescribed medication.
KEY INFORMATION
• EFSA indicated 800 mg of EGCG per day from supplements as the threshold at which aminotransferase activity increases, not as a safe dose (EFSA, EFSA Journal, 2018).
• Catechins reduced body weight by an average of 1.31 kg in a meta-analysis of 11 studies (Hursel, International Journal of Obesity, 2009).
• The bioavailability of free EGCG is over 3.5 times higher on an empty stomach than after a meal, although nausea occurs more frequently on an empty stomach (Chow, Clinical Cancer Research, 2005).
• Green tea reduced nadolol levels in the blood by 85% and weakened its effect on blood pressure (Misaka, Clinical Pharmacology and Therapeutics, 2014).
• In the Ohsaki cohort, cancer mortality did not differ significantly between green tea consumption groups (Kuriyama, JAMA, 2006).
What is EGCG and how much does tea provide compared to supplements?
EGCG belongs to catechins, which are flavonoids with antioxidant properties, and is the dominant fraction among them. Black tea undergoes fermentation, during which catechins oxidize to theaflavins; green tea is subjected to heat treatment after harvesting that halts this process, thus retaining more catechins. However, the difference between the drink and the capsule is not solely based on quantity.
The EFSA opinion provides specific exposure ranges. The average daily intake of EGCG from green tea infusions in the adult population of the European Union ranges from 90 to 300 mg, and among those who drink the most, it reaches 866 mg per day. Dietary supplements with catechins provide between 5 and 1000 mg of EGCG per day. The panel deemed catechins from traditionally brewed infusions to be generally safe at consumption levels reported in member states, while also noting rare cases of liver damage after infusions, most likely of an idiosyncratic nature.
| Data source | Czego dotyczy | Value provided by the authors |
|---|---|---|
| EFSA, EFSA Journal, 2018 | EGCG intake from infusions, adults in the European Union | On average, 90-300 mg per day; among the highest consumers, up to 866 mg per day |
| EFSA, EFSA Journal, 2018 | EGCG content in dietary supplements | From 5 to 1000 mg per day |
| EFSA, EFSA Journal, 2018 | Threshold for increased aminotransferases in interventional studies | Od 800 mg EGCG dziennie z suplementu |
| Chow, Clinical Cancer Research, 2005 | 30 healthy volunteers, single dose of Polyphenon E, alternating regimen | Maximum concentration of free EGCG over 3.5 times higher in fasting than after a light meal |
| Hursel, International Journal of Obesity, 2009 | Meta-analysis of 11 studies on body weight | Average change in body weight -1.31 kg compared to control (p below 0.001) |
| Misaka, Clinical Pharmacology and Therapeutics, 2014 | 10 volunteers, nadolol with green tea or water | Decrease in maximum nadolol concentration by 85.3% and area under the curve by 85.0% |
Does EGCG absorb better with a meal or on an empty stomach?
On an empty stomach, and quite clearly. The notion of significantly better absorption with a fatty meal circulates in supplement descriptions in reverse form. A pharmacokinetic study in 30 healthy volunteers administered Polyphenon E in an alternating regimen: once after overnight fasting, once with a light breakfast. The maximum concentration of free EGCG in plasma was over 3.5 times higher in fasting, and similarly, free epigallocatechin and epicatechin gallate behaved.Chow, Clinical Cancer Research, 2005).
This does not mean that taking it on an empty stomach is a better idea. In the same study, mild, transient nausea occurred most often precisely on an empty stomach and with the highest tested amount of extract. The authors also noted that a preparation providing up to 800 mg of EGCG was well tolerated on an empty stomach, but this is an observation from a single dose, not from continuous supplementation, to which the EFSA warning refers.
The practical conclusion is therefore uncomfortable for both camps. A meal lowers the concentration of free catechins in the blood, while simultaneously alleviating gastrointestinal symptoms and reducing the liver's exposure to high peak concentrations. A review on the metabolic syndrome states directly that the optimal dose of green tea catechins has not yet been established.Thielecke i Boschmann, Phytochemistry, 2009). In the absence of such a value, the method of intake is determined with a doctor or pharmacist.
Does EGCG help with weight loss, and by how much?
It helps to a degree that is easy to overestimate: on average, just over a kilogram. A meta-analysis of eleven studies showed that catechins significantly reduced body weight and helped maintain it after a weight loss period, with an average change of 1.31 kg compared to the control group and a p-value below 0.001. The authors also checked what weakens this effect: high habitual caffeine intake, above 300 mg per day, reduced it from 1.60 kg to 0.27 kg, although this difference did not reach significance.Hursel, International Journal of Obesity, 2009).
A second meta-analysis by the same team measured metabolism directly in respiratory chambers. Mixtures of catechins with caffeine increased daily energy expenditure by 428 kJ, or 4.7%, and daily fat oxidation by 12.2 g, or 16.0%. Caffeine alone raised energy expenditure almost identically, but its effect on fat oxidation was not statistically significant.Hursel, Obesity Reviews, 2011).
From these two studies, a point emerges that advertisements overlook. The increase in calorie burning is largely attributed to caffeine, while catechins mainly contribute to fat oxidation. A person who drinks a lot of coffee has less to gain, and a caffeine-free preparation works less effectively on energy expenditure. We discuss how caffeine from various plants behaves in the body in our article on yerba mate i kofeinie.
What do studies say about green tea and the heart?
The largest data comes from the Japanese Ohsaki cohort, which included 40,530 people aged 40 to 79, observed for up to eleven years. Among women drinking five or more cups daily, cardiovascular mortality was lower, with a hazard ratio of 0.69 with a confidence interval from 0.53 to 0.90 and a significant trend. Among men in the same consumption group, overall mortality had a hazard ratio of 0.88 with a range from 0.79 to 0.98. The strongest association concerned deaths from stroke.Kuriyama, JAMA, 2006).
This is an observational study, so it shows correlation, not causation. People who drink a lot of green tea may differ from the rest of the population in terms of diet, activity, and habits, which no statistical adjustment can fully eliminate. The authors note that for overall mortality, the association was stronger in women, and the interaction with sex reached statistical significance; for cardiovascular mortality, the same interaction did not achieve significance.
A review on the metabolic syndrome cautiously summarizes this area: most epidemiological and interventional studies in humans show a beneficial effect of catechins on body weight, glycemic control, and cardiovascular risk factors, but the number of studies in humans is still small, and the mechanisms have mainly been described in cell and animal models. The area of neuroprotection looks similar: a study showing that EGCG reduces amyloid beta deposition concerned cells and transgenic mice, not patients.Rezai-Zadeh, Journal of Neuroscience, 2005).
Does green tea reduce cancer risk?
The data is inconsistent, and the largest study turned out negative. In the Ohsaki cohort, cancer mortality did not significantly differ from unity in any category of green tea consumption, even though overall and cardiovascular mortality decreased with the number of cups consumed. The authors concluded directly: green tea consumption is associated with lower overall and cardiovascular mortality, but not with lower cancer mortality.
An earlier, smaller prospective study in Saitama Prefecture measured something different, as incidence rather than mortality, and there the result was positive, though only in women. It included 8,552 people over forty, observed for nine years, during which 384 cancer cases were recorded. In the highest consumption group, the relative risk was 0.57 in women, with a confidence interval from 0.33 to 0.98, and 0.68 in men, with a range from 0.39 to 1.21, which was not significant in men.Imai, Preventive Medicine, 1997).
The popular summary of this work states that the onset of cancer was delayed by seven years in men. This is doubly misleading: the effect concerned women, and in men, it did not reach statistical significance. The pharmacological review of green tea also emphasizes that transferring results from cell cultures to humans is complicated by the low bioavailability of catechins and the discrepancy between concentrations studied in vitro and those achievable in plasma.Zaveri, Life Sciences, 2006).
When does EGCG burden the liver and what symptoms should raise concern?
The threshold set by EFSA is 800 mg of EGCG per day taken in the form of a dietary supplement. Above this value, interventional studies have shown a statistically significant increase in serum aminotransferase activity in treated individuals compared to controls. The panel did not establish a safe consumption level for catechins from supplements, and traditional brews were assessed separately and more leniently.
Symptoms that warrant immediate cessation of supplementation are typical of liver damage: nausea, abdominal pain, jaundice of the skin or the whites of the eyes, dark urine, and unusual fatigue. Each of these is a reason to contact a doctor, not to wait it out. The risk increases with prolonged use of high amounts and with products of unknown purity.
It is worth remembering the proportions. A brew usually provides several times less EGCG than a capsule with concentrated extract, and rare cases of liver damage from brews are described by EFSA as idiosyncratic reactions, meaning unpredictable and not related to quantity. A supplement is a different category of exposure than drinking tea, although the labels of both suggest the same plant. A comparison with other brews high in polyphenols can be found in the text about chadze i jej antyoksydantach.
What drugs interact with EGCG and how to choose an extract?
Two interactions are documented strongly enough to change the decision about supplementation. The first concerns nadolol: in a study with ten volunteers, drinking green tea for fourteen days reduced the maximum concentration of this beta-blocker by 85.3%, and the area under the curve by 85.0%, while also weakening its effect on systolic blood pressure. The mechanism is the inhibition of the OATP1A2 transporter in the intestine (Misaka, Clinical Pharmacology and Therapeutics, 2014).
The second concerns bortezomib used in multiple myeloma. In cell and animal models, polyphenols from green tea, primarily EGCG, negated the anticancer effects of this drug, reacting directly with it and blocking proteasome inhibition. The authors suggest that consuming green tea products may be contraindicated during bortezomib therapy (Golden, Blood, 2009).
When choosing a product, pay attention to three things. The label should provide the content of EGCG in milligrams, not just the mass of the extract, as without this, one cannot relate the product to the values from the EFSA opinion. Information about caffeine content determines whether the product is suitable for the evening. An analysis certificate from an independent laboratory protects against contaminants, which in some documented cases of liver damage were found to be co-responsible. How such declarations look for other standardized extracts is shown in the text about sulforaphane from broccoli.
Frequently Asked Questions
Did EFSA consider 800 mg of EGCG daily to be safe?
No. The opinion from 2018 indicates that 800 mg of EGCG per day from a dietary supplement is the value from which interventional studies showed a significant increase in aminotransferase activity. For catechins from supplements, the panel did not establish a safe intake level. This is a warning, not a recommendation.
Does EGCG help with weight loss?
To a modest extent. A meta-analysis of eleven studies showed an average body weight change of 1.31 kg compared to controls. The effect weakened in individuals with high habitual caffeine intake. Catechins support diet and physical activity, but the magnitude of this change cannot be compared to the effect of lifestyle changes alone.
Should EGCG be taken on an empty stomach or with a meal?
Free catechins are absorbed more than 3.5 times better on an empty stomach, but nausea occurs more frequently on an empty stomach, and peak concentrations are highest. The optimal dose or method of administration has not been established in studies, so it is worth discussing the decision with a doctor or pharmacist, especially in the case of liver disease.
Does green tea protect against cancer?
The data is inconsistent. In the largest Japanese cohort, cancer mortality did not differ significantly between green tea consumption groups, although overall and cardiovascular mortality was lower. A smaller study from Saitama Prefecture showed a lower risk of disease, but only in women.
Does EGCG interact with medications?
Yes, and it's serious. Green tea reduced nadolol levels by 85% and weakened its effect on blood pressure. In preclinical studies, EGCG negated the anticancer effect of bortezomib. For chronic medications, supplementation should be preceded by a conversation with the attending physician.
Standardized plant extracts with declared active substance content are grouped in the category plant extracts; before purchasing, compare labels for EGCG and caffeine content.
This article is for informational and educational purposes and does not constitute medical advice. Before starting supplementation, consult your doctor, especially if you are taking medications regularly, are pregnant or breastfeeding, or have a chronic illness.
Author: Michał Waluk · Opublikowano: 2026-07-15 · Aktualizacja: 2026-08-11
