EGCG

What is EGCG?

EGCG (epigallocatechin gallate) is an antioxidant from the catechin group — the most active and most studied compound in green tea. About 30% of the dry weight of a green tea leaf is made up of catechins, and EGCG is the dominant one — about 50%–60% of all the catechins in the leaf. When a supplement label promises “green tea extract,” the extract is in most cases standardized by its percentage of EGCG.

Catechins are a subfamily of polyphenols — the protective compounds the plant produces for itself. What sets EGCG apart within this family is a combination of high antioxidant potency and the ability to cross the blood-brain barrier, alongside one fundamental drawback: poor absorption in the human body.

In brief: EGCG in a few lines

• What it is: the main catechin in green tea. Full name: epigallocatechin gallate.
• What it does: slows the breakdown of noradrenaline (hence the link to fat burning), inhibits the NF-κB inflammatory pathway, slows sugar absorption in the gut and protects LDL from oxidation.
• How much is in a cup: 20–50 mg in regular green tea, 70–130 mg in matcha.
• Effective dose: 200–400 mg a day — that is, 3–5 cups of tea, or a standardized supplement.
• When to be careful: above 800 mg a day from a concentrated extract, when taken on an empty stomach, or when combined with iron supplements and blood thinners.

For information on the drink itself — benefits, downsides and preparation — see green tea, and for the concentrated supplement see green tea extract.

How much EGCG is in a cup of tea?

Sources of EGCG by descending concentration:

A heat warning: EGCG breaks down quickly when tea is made with boiling water (100°C / 212°F). To get the most catechins, use water at 70–80°C (158–176°F) and steep the leaves for one to three minutes.

What EGCG does in the body

The science behind the “fat burner”

How does it work? EGCG inhibits an enzyme called COMT, whose job is to break down the hormone noradrenaline. When the enzyme is inhibited, noradrenaline levels stay higher for longer. Noradrenaline is what gives fat cells the command to break down fat and release it into the bloodstream as available energy. Studies have shown that combining EGCG with caffeine is particularly effective (synergy), raising resting metabolic rate by about 4%.

Cardiovascular effects

Meta-analyses of observational studies show that regular green tea consumption (3–5 cups a day) is associated with a roughly 10–20% lower risk of stroke and coronary heart disease compared with a population that does not drink tea. This is a statistical association, not proven causation. The main mechanisms:

• Inhibiting LDL oxidation: EGCG protects LDL from oxidation by free radicals, a critical step in the development of atherosclerosis.
• Improving endothelial function: it increases nitric oxide (NO) production in blood vessels, which widens arteries and lowers systolic blood pressure by an average of 2–3 mmHg.
• Reducing platelet aggregation: it inhibits the clumping of blood platelets — in the same direction as low-dose aspirin, but much more weakly.

Neuroprotective effects

EGCG is one of the few polyphenols that manages to cross the blood-brain barrier. Inside the brain it acts on several levels:

• Alzheimer’s disease: it inhibits the aggregation of beta-amyloid and tau proteins — the two pathological markers of the disease. Studies in mice with Alzheimer’s mutations showed a reduction of up to 50% in amyloid plaques after EGCG administration.
• Parkinson’s disease: it protects dopaminergic neurons from oxidative damage caused by MPTP (a toxin that mimics Parkinson’s in animals).
• General neurodegeneration: it increases production of BDNF (brain-derived neurotrophic factor) — a protein considered “fertilizer” for brain cells. It is important to note: most of the evidence is still preclinical. Studies in humans point to an epidemiological association only, not proven causation.

A weapon against cancer?

Dozens of laboratory (in vitro) and animal studies have demonstrated EGCG’s ability to:

1. Inhibit angiogenesis: preventing the formation of new blood vessels that feed the tumor.
2. Apoptosis: triggering programmed “suicide” of cancer cells without harming healthy cells.
3. Neutralize free radicals: protecting DNA from oxidative damage that can lead to cancerous mutations. It is important to note: studies in humans have not yet reached conclusions as clear-cut as in the lab, but the direction is promising.

Regulating blood sugar and insulin levels

EGCG acts on the insulin pathway at several points at once:

1. Inhibiting amylolytic enzymes: it inhibits alpha-amylase and alpha-glucosidase in the small intestine — enzymes that break carbohydrates down into glucose. This inhibition slows the rate at which sugar is absorbed into the blood and prevents large spikes.
2. Boosting GLUT4: it increases translocation of glucose transporters (GLUT4) to the membrane of muscle cells, allowing the cells to take up glucose even in the absence of insulin.
3. Reducing insulin resistance: in clinical trials in people with type 2 diabetes, taking 400 mg of EGCG a day led to a slight drop in HbA1c (glycated hemoglobin) after 12 weeks. Combining it with a carbohydrate-rich meal can lower the meal’s glycemic index.

Anti-inflammatory effect

EGCG directly inhibits the NF-κB pathway — the immune system’s main inflammation switch. When this pathway is overactive it leads to excess production of pro-inflammatory cytokines (IL-6, TNF-α, IL-1β) linked to chronic inflammation, autoimmune diseases and excess weight. In addition, EGCG inhibits the COX-2 enzyme — the same enzyme targeted by drugs like ibuprofen, but to a more moderate degree.

The absorption problem (bioavailability)

The bad news is that EGCG is very poorly absorbed in the human body. Most of it breaks down in the intestines or is excreted. How can you improve absorption?

• Vitamin C: combining it with lemon or orange raises absorption up to 5-fold.
• Piperine (black pepper): improves absorption (as with turmeric).
• A supplement on an empty stomach: better absorption (but see the warning in the Q&A).

Downsides and side effects of EGCG

This is the side that matters especially when it comes to a concentrated supplement rather than a drink.

• Liver toxicity — the most significant downside: concentrated green tea extracts have been linked to cases of acute liver damage (hepatotoxicity). The phenomenon is rare, but it is well documented, and it led health authorities in Europe to consider restrictions on EGCG doses in supplements. The risk rises at high doses (above 800 mg of EGCG a day), when taken on an empty stomach, and when combined with alcohol. It is important to stress: the problem concerns concentrated supplements, not drinking green tea — no liver damage has been documented from drinking tea in normal amounts.
• Nausea and stomach pain on an empty stomach: catechins irritate the stomach lining. This is also why taking it on an empty stomach — which improves absorption — increases the risk of side effects.
• Inhibiting iron absorption: EGCG binds non-heme iron and significantly reduces its absorption. This is especially relevant for vegetarians, vegans and people with anemia. Separate it from iron-rich meals by one to two hours.
• Drug interactions: EGCG may reduce the effectiveness of bortezomib (a chemotherapy drug), affect anticoagulants, and interact with drugs broken down by CYP enzymes.
• Accompanying caffeine: many green tea extracts also contain caffeine, which can cause restlessness and sleep disturbances.
• Pregnancy and breastfeeding: EGCG supplements are not recommended. In addition, EGCG may interfere with the metabolism of folic acid.
• The gap between the lab and the body: most of EGCG’s impressive results were achieved in cell cultures at concentrations that cannot be reached in the human body through food. Combined with the poor absorption, marketing promises should be treated with caution.