Epigallocatechin gallate, usually called EGCG, is the most abundant and most studied antioxidant in green tea. It belongs to a class of plant compounds called catechins, which fall under the broader flavonoid family. A typical cup (250 mL) of brewed green tea delivers roughly 50 to 100 mg of EGCG, and it accounts for 50 to 65% of all the catechins in the tea leaf. This single compound is responsible for much of what makes green tea a subject of ongoing health research.
How EGCG Works in the Body
EGCG is primarily an antioxidant, meaning it neutralizes unstable molecules called free radicals that damage cells. It does this by donating hydrogen atoms or electrons from its chemical structure, directly scavenging several types of reactive oxygen species. But its effects go well beyond simple antioxidant activity.
EGCG also influences how genes are expressed. It can block an enzyme called DNA methyltransferase, which controls whether certain genes are switched on or off. This type of influence, known as epigenetic modification, is one reason researchers have been particularly interested in its potential role in cancer biology. It also dials down a key inflammatory signaling pathway (NF-κB), which plays a role in cell survival, migration, and the growth of new blood vessels that tumors rely on.
Where You’ll Find the Most EGCG
Not all teas are equal when it comes to EGCG content. Green tea is the richest source because the leaves are minimally oxidized during processing. Black tea, by contrast, undergoes full oxidation, which converts most catechins into different compounds. Even within green tea, the range is wide. Testing of commercially available products found EGCG concentrations ranging from about 23 mg per gram of tea leaves in some bagged teas to over 70 mg per gram in loose-leaf gunpowder-style green tea.
Matcha is often promoted as an EGCG powerhouse because you consume the whole ground leaf rather than steeping and discarding it. Lab testing of popular brands found culinary matcha averaging around 37 to 62 mg of EGCG per gram, and ceremonial matcha in a similar range of 49 to 70 mg per gram. The actual amount you get in a cup depends heavily on how much tea you use and how it’s prepared, but matcha’s advantage is that nothing gets left behind in a tea bag.
Effects on Heart Health
A meta-analysis of randomized clinical trials found that green tea consumption lowered systolic blood pressure by about 1.94 mmHg on average. It also reduced total cholesterol and LDL (“bad”) cholesterol by modest but statistically significant amounts. However, it had no meaningful effect on diastolic blood pressure, HDL (“good”) cholesterol, or triglycerides. These are small shifts at the individual level, but across a population, even a 2-point drop in systolic blood pressure can translate into meaningful reductions in cardiovascular events.
Fat Burning and Metabolism
EGCG has a measurable effect on how the body uses fat for fuel during exercise. In one study of overweight, recreationally active adults, eight weeks of supplementation with decaffeinated green tea extract increased the contribution of fat to energy expenditure from about 21% to nearly 35% during exercise. The intensity at which the body stopped burning fat also shifted upward by 22.5%, meaning participants could exercise harder before their bodies switched entirely to burning carbohydrates. These findings suggest EGCG may enhance fat oxidation, though weight loss outcomes in broader research have been modest.
Cancer Research: Promising but Incomplete
EGCG has shown anticancer activity in lab dishes and animal studies across a wide range of cancer types, including skin, lung, breast, prostate, liver, stomach, and colon cancers. It inhibits tumor growth through multiple routes: triggering cell death in cancer cells, blocking the formation of new blood vessels that feed tumors, and interfering with cell migration.
Human evidence is more mixed. A large prospective study of over 8,000 people in Japan found that daily green tea consumption was associated with delayed cancer onset. A follow-up in breast cancer patients found lower recurrence rates among green tea drinkers with early-stage disease. One clinical trial found that 200 mg of EGCG daily for 12 weeks was effective in patients with HPV-related cervical lesions. Still, epidemiological studies overall have produced inconsistent results, and EGCG is not considered a proven cancer treatment or prevention strategy in humans.
Absorption: Timing Matters
One of EGCG’s biggest limitations is poor bioavailability. Your body absorbs only a fraction of what you consume, and food makes this significantly worse. When healthy volunteers took EGCG capsules on an empty stomach after an overnight fast, their blood levels were 2.7 times higher than when they took the same capsules with a light breakfast, and 3.9 times higher than when the EGCG was embedded in food. The food didn’t speed up how quickly EGCG was cleared from the bloodstream; it simply blocked absorption in the gut.
If you’re drinking green tea for general enjoyment, this distinction is mostly academic. But if you’re taking concentrated EGCG supplements and want maximum absorption, taking them with water on an empty stomach makes a substantial difference.
Safety and Liver Risk
EGCG from brewed tea is generally well tolerated. The concern arises with concentrated supplements. High doses of green tea extract have been linked to liver damage in some individuals, prompting the European Food Safety Authority to recommend keeping EGCG intake from supplements below 800 mg per day. For context, you would need to drink roughly 8 to 16 cups of green tea to reach that threshold from beverages alone, which is difficult to do accidentally. Supplement capsules, however, can easily deliver 400 to 500 mg in a single pill, making it possible to exceed safe levels with just one or two doses.
Genetic variation also plays a role. People differ in how efficiently their liver processes EGCG based on the activity of specific detoxification enzymes. This means some individuals may be more susceptible to liver stress at doses that others tolerate without issue.
Drug Interactions to Watch For
EGCG can alter how your body absorbs and processes several common medications. The most dramatic interaction is with nadolol, a blood pressure medication: green tea reduced the drug’s absorption by 85% and significantly weakened its blood pressure-lowering effect. For people relying on nadolol to manage hypertension, this is a clinically meaningful interaction.
Green tea also affects cholesterol-lowering statins. It reduced absorption of rosuvastatin by about 19%, while it increased blood levels of simvastatin’s active form by 22%. The direction of the interaction depends on which transport proteins and liver enzymes are involved. EGCG increased blood levels of sildenafil (used for erectile dysfunction and pulmonary hypertension) by roughly 50%, and doubled blood levels of tacrolimus, an immune-suppressing drug used after organ transplants. It also reduced the effectiveness of warfarin, a blood thinner, by supplying vitamin K and lowering the key clotting measure (INR) from a therapeutic 3.79 to a subtherapeutic 1.37 in one documented case.
These interactions become more likely at higher intakes, whether from concentrated supplements, large volumes of green tea, or strong infusions. If you take any of these medications, it’s worth discussing your green tea and supplement habits with a pharmacist or prescriber.