Catechins are a group of natural antioxidant compounds found most abundantly in tea leaves, but also in fruits, wine, and cocoa. They belong to the flavonoid family, a broad class of plant-based chemicals with well-studied health effects. Green tea is the richest common dietary source, containing roughly 125 mg of catechins per 100 g of brewed tea, compared to about 26 mg in the same amount of black tea. Their antioxidant, cardiovascular, and metabolic effects have made catechins one of the most researched plant compounds in nutrition science.
The Four Main Types
While dozens of catechin variants exist in nature, four account for the vast majority found in tea and the ones studied most in humans:
- EGCG (epigallocatechin gallate): The most abundant and most potent catechin in green tea. It drives most of the health effects attributed to tea consumption.
- EGC (epigallocatechin): The second most common in green tea, with moderate antioxidant activity.
- ECG (epicatechin gallate): Present in smaller amounts but notable for strong free-radical scavenging.
- EC (epicatechin): Found in tea, cocoa, apples, and red wine. It has the highest absorption rate of the four.
The “gallate” types (EGCG and ECG) carry an extra chemical group that gives them stronger antioxidant capacity but also makes them harder for the body to absorb.
How Catechins Work as Antioxidants
Catechins protect cells through several overlapping mechanisms, not just one. Their most direct action is intercepting free radicals before those molecules can damage cell membranes and DNA. They act as chain-breaking antioxidants, neutralizing the reactive molecules that drive lipid peroxidation, a process where fats in cell membranes degrade and contribute to chronic disease.
The strength of this effect depends on the number and arrangement of hydroxyl groups on the catechin molecule. Having a pair of adjacent hydroxyl groups on one part of the molecule, plus a galloyl group in another position, is what makes EGCG and ECG especially effective scavengers.
Catechins also bind to metal ions like iron and copper, forming inactive complexes that prevent those metals from triggering further oxidative reactions. Beyond this direct chemistry, catechins activate the body’s own antioxidant defenses. They switch on a signaling pathway (often called the Nrf2 pathway) that ramps up production of protective enzymes, including glutathione, superoxide dismutase, and catalase. These are the same enzymes your cells rely on to clean up oxidative damage from everyday metabolism, exercise, and environmental stress.
Cardiovascular Effects
One of the best-supported benefits of catechins is their effect on blood vessels. EGCG and EC both stimulate the production of nitric oxide in the cells lining blood vessel walls. Nitric oxide is the molecule that tells blood vessels to relax and widen, which lowers blood pressure and improves blood flow. Lab studies show catechins activate the enzyme responsible for making nitric oxide, and this translates to measurable vasodilation in isolated blood vessels.
Catechins also reduce oxidative stress in artery walls, which is one of the early steps in atherosclerosis. By limiting the oxidation of LDL cholesterol and suppressing inflammatory signaling inside vessel walls, catechins help slow the buildup of arterial plaque. This combination of effects, better vessel flexibility plus less oxidative damage, is why regular tea consumption is consistently linked to lower cardiovascular risk in population studies.
Metabolism and Fat Burning
Catechins have a modest but measurable effect on how the body burns fat. In one controlled trial, a decaffeinated green tea extract providing 366 mg of EGCG per day increased fat oxidation by about 17% after a single dose and by roughly 25% after four weeks of daily use. These effects appear to come from catechins’ ability to prolong the activity of noradrenaline, a hormone that signals fat cells to release stored energy.
This mechanism is amplified when catechins are consumed alongside caffeine, which is why green tea (naturally containing both) tends to show stronger metabolic effects than catechin supplements alone. The two compounds work along the same signaling chain: caffeine prevents the breakdown of a key messenger molecule inside cells, while catechins prevent the breakdown of noradrenaline outside cells. Together, they increase the expression of enzymes that break down stored fat. The effect is real but not dramatic. It’s a subtle metabolic nudge, not a substitute for exercise or dietary changes.
Food Sources and Amounts
Green tea is the standout source. A 100 g serving of brewed green tea delivers around 8 mg of epicatechin plus over 114 mg of the three larger catechins (EGC, ECG, and EGCG) combined. Decaffeinated green tea retains a significant portion, with roughly 50 mg of those same catechins per 100 g. Oolong tea falls in the middle at about 47 mg, while black tea drops to around 23 mg because the fermentation process converts catechins into other compounds.
Outside of tea, catechins show up in places you might not expect. Blackberries contain about 37 mg of catechin per 100 g. Black diamond plums provide around 18 mg, plus an additional 13 mg of the larger catechin types. Red wine ranges from 8 to 30 mg of catechin per 100 g depending on the variety, with Cabernet Sauvignon also contributing 11 mg of epicatechin. Apples are a reliable daily source, with Granny Smith apples providing about 2 mg of catechin and 7 mg of epicatechin per 100 g of raw fruit with skin. Almonds, pecans, and pears contribute smaller but consistent amounts.
How Well the Body Absorbs Them
Catechins are not particularly well absorbed. After an oral dose, blood levels peak about two hours later, but the overall bioavailability varies dramatically between types. Epicatechin (EC) has the best absorption rate at around 39%. EGCG, despite being the most potent antioxidant of the group, has a bioavailability of only about 14%. ECG is the lowest at roughly 6%.
Several factors explain this. Catechins pass through the liver before reaching general circulation, and much of the dose is metabolized during that first pass. They also distribute widely into tissues rather than staying concentrated in the blood, with an apparent volume of distribution ranging from 30 to 63 liters per kilogram. This means blood measurements underestimate how much actually reaches your organs. Consuming catechins with food, particularly vitamin C-rich foods, and avoiding dairy (which can bind to the compounds) may improve absorption, though the evidence on these strategies is mixed.
Safety and Upper Limits
Catechins from brewed tea have an excellent safety record. The concern arises with concentrated green tea extract supplements, particularly when taken on an empty stomach. A systematic review of 159 human studies found that liver injury is the primary risk, and it occurs almost exclusively with high-dose, concentrated solid supplements taken as a single bolus, not from drinking tea.
Based on toxicological and human safety data, a safe daily limit of 338 mg of EGCG applies to concentrated supplement forms (capsules or tablets). For catechins consumed as part of a beverage, such as brewed tea or liquid extracts, the observed safe level is higher at 704 mg of EGCG per day. To put that in context, a typical cup of green tea contains roughly 50 to 100 mg of EGCG, so you would need to drink seven or more cups daily to approach the beverage limit. Most people drinking a few cups of green tea a day are well within safe territory. If you use a concentrated supplement, taking it with food rather than on an empty stomach significantly reduces the risk of liver stress.