Green Tea and Cancer: What EGCG Does Inside the Cell

A compound found in every cup of green tea can slow cancer cell growth, trigger cancer cell death, and switch silenced tumour-suppressing genes back on – at least in laboratory and animal studies. That compound is epigallocatechin-3-gallate, or EGCG, and it is the most intensively studied plant-derived molecule in cancer prevention research. Decades of cell culture experiments, animal trials, and population studies have built a substantial – if still incomplete – case that EGCG interferes with cancer at multiple biological levels [1,2,3].

The Bottom Line Up Front

EGCG does not cure cancer. No food does. But among the thousands of plant chemicals tested in laboratories, EGCG stands out because it hits so many of the cellular processes that cancer cells rely on: unchecked growth, resistance to programmed cell death, inflammation, and the ability to silence protective genes. These findings come primarily from laboratory and animal work; large-scale human clinical trials remain limited, and a 2020 Cochrane systematic review of 142 studies concluded that the overall evidence for green tea reducing cancer risk is still “limited” and “inconsistent” [4]. What makes EGCG remarkable is not a single dramatic result, but the sheer breadth of biological mechanisms it influences.

What EGCG Is

Green tea comes from the leaves of Camellia sinensis. Unlike black tea, green tea leaves undergo minimal processing, which preserves a family of antioxidant molecules called catechins. EGCG is the most abundant and biologically active of these catechins, making up the majority of green tea’s total catechin content [5]. It is also the most potent: cell culture studies consistently show EGCG outperforms other tea catechins in blocking cancer-related signalling pathways [3].

How EGCG Fights Cancer Cells: Four Key Mechanisms

1. Blocking the growth-and-survival pathway. Many cancers hijack a cellular signalling chain known as PI3K/Akt/mTOR. This pathway normally tells cells when to grow and divide, but in cancer it gets stuck in the “on” position, driving uncontrolled multiplication and helping tumour cells resist death. EGCG has been shown to dial down this pathway across multiple cancer cell types – including breast, lung, colorectal, prostate, and melanoma – by reducing the activity of key proteins (phospho-Akt and mTOR) and tipping the balance of cell-death regulators in favour of apoptosis, the body’s natural process for eliminating damaged cells [6,7,8].

2. Boosting the cell’s own defences while calming inflammation. EGCG activates a molecular switch called Nrf2, which turns on a suite of protective genes that produce antioxidant enzymes. These enzymes neutralise harmful molecules called reactive oxygen species (ROS) and help detoxify cancer-causing chemicals [9,10]. At the same time, EGCG suppresses NF-κB, a different molecular switch that drives chronic inflammation – a known contributor to cancer development. This dual action – ramping up cellular protection while dampening inflammation – has been documented in multiple cancer types [3,10,11,12].

3. Reducing inflammation directly. Beyond the NF-κB pathway, EGCG lowers the activity of COX-2, an enzyme that fuels the inflammatory cascade, and reduces levels of inflammatory signalling molecules (TNF-α, IL-1β, and IL-6). These anti-inflammatory effects are especially relevant for cancers of the digestive system – stomach, colon, and liver – where chronic inflammation is a well-established driver of tumour formation [12,13,14].

4. Reversing gene silencing. Cancer cells often shut down their own tumour-suppressing genes by attaching chemical tags (methyl groups) to their DNA, a process called hypermethylation. EGCG directly inhibits the enzyme (DNMT1) responsible for maintaining these silencing tags. In laboratory experiments on oesophageal, colon, and prostate cancer cells, EGCG treatment reactivated several important tumour suppressor genes – including p16, RAR-beta, and MGMT – that had been silenced by methylation [15]. EGCG also inhibits another class of enzymes called histone deacetylases (HDACs), which affect how tightly DNA is packaged and therefore how accessible genes are for activation. In prostate cancer cells, green tea polyphenols reduced HDAC activity and reactivated the TIMP-3 gene, which helps prevent cancer from spreading [16,17].

What Population Studies Show

Large observational studies – particularly in East Asian populations where green tea consumption is high – have found associations between regular tea drinking and reduced risk of certain cancers, including stomach, oesophageal, and prostate cancer [1,2]. A 2022 UK Biobank study of nearly 500,000 people found that drinking two or more cups of tea per day was associated with lower overall mortality, including from cardiovascular disease [18]. However, these are observational findings – they show correlations, not proof of cause and effect.

The most rigorous assessment to date, a 2020 Cochrane systematic review that analysed 11 randomised controlled trials and 131 observational studies involving over 1.1 million participants, found that the evidence remains inconsistent across cancer types. Some case-control studies suggested reduced risk, but cohort studies – generally considered more reliable – often showed conflicting results. The reviewers concluded that well-conducted, adequately powered clinical trials are still needed before any firm conclusions can be drawn [4].

Important Caveats

Most of the mechanistic evidence for EGCG comes from cell culture and animal experiments, which use concentrations higher than what the body typically absorbs from drinking tea. EGCG has low oral bioavailability – much of it is broken down in the gut or chemically modified by the liver before it can reach target tissues. A 2025 review in Advances in Nutrition noted that absorption is limited in the small intestine and that extensive metabolism (including methylation, glucuronidation, and sulfation) further reduces the amount of active EGCG in the bloodstream [19]. High-dose green tea extract supplements have also been linked to liver injury in some cases, prompting the United States Pharmacopeia to add cautionary labelling to concentrated green tea extract products [20].

None of this invalidates the laboratory findings, but it places them in context. Green tea is not chemotherapy. The research supports EGCG as one of the most thoroughly studied plant-derived chemopreventive agents available – a dietary component that, as part of a balanced diet, may support the body’s natural defences against cancer development [3,5].

References

1. Xu Y, Zhang M, Wu T, Dai S, Xu J and Zhou Z (2020) Tea and cancer prevention: an evaluation of the pharmacological evidence. Crit Rev Food Sci Nutr 60:2574–2601. doi:10.1080/10408398.2018.1549756.
2. Yang CS, Wang X, Lu G and Picinich SC (2009) Cancer prevention by tea: animal studies, molecular mechanisms and human relevance. Nat Rev Cancer 9:429–439. doi:10.1038/nrc2641.
3. Singh BN, Shankar S and Srivastava RK (2011) Green tea catechin, epigallocatechin-3-gallate (EGCG): mechanisms, perspectives and clinical applications. Biochem Pharmacol 82:1807–1821. doi:10.1016/j.bcp.2011.07.093.
4. Filippini T, Malavolti M, Borrelli F, Izzo AA, Fairweather-Tait SJ, Horneber M and Vinceti M (2020) Green tea (Camellia sinensis) for the prevention of cancer. Cochrane Database Syst Rev 3:CD005004. doi:10.1002/14651858.CD005004.pub3.
5. Khan N and Mukhtar H (2019) Tea polyphenols in promotion of human health. Nutrients 11:39. doi:10.3390/nu11010039.
6. Ferrari E, Bettuzzi S and Naponelli V (2022) The potential of epigallocatechin gallate (EGCG) in targeting autophagy for cancer treatment: a narrative review. Int J Mol Sci 23:6075. doi:10.3390/ijms23116075.
7. Du BX, Lin P and Lin J (2022) EGCG and ECG induce apoptosis and decrease autophagy via the AMPK/mTOR and PI3K/AKT/mTOR pathway in human melanoma cells. Chin J Nat Med 20:290–300. doi:10.1016/S1875-5364(22)60166-3.
8. Alam M, Gulzar M, Akhtar MS, Rashid S, Zulfareen, Tanuja, Shamsi A and Hassan MI (2024) Epigallocatechin-3-gallate therapeutic potential in human diseases: molecular mechanisms and clinical studies. Mol Biomed 5:73. doi:10.1186/s43556-024-00240-9.
9. Lee HW, Choi JH, Seo D et al. (2024) EGCG-induced selective death of cancer cells through autophagy-dependent regulation of the p62-mediated antioxidant survival pathway. Biochim Biophys Acta Mol Cell Res 1871:119659. doi:10.1016/j.bbamcr.2024.119659.
10. Huang YJ, Wang KL, Chen HY, Chiang YF and Hsia SM (2020) Protective effects of epigallocatechin gallate (EGCG) on endometrial, breast, and ovarian cancers. Biomolecules 10:1481. doi:10.3390/biom10111481.
11. Surh YJ, Chun KS, Cha HH et al. (2001) Molecular mechanisms underlying chemopreventive activities of anti-inflammatory phytochemicals: down-regulation of COX-2 and iNOS through suppression of NF-κB activation. Mutat Res 480–481:243–268. doi:10.1016/s0027-5107(01)00183-x.
12. Ohishi T, Goto S, Monira P, Isemura M and Nakamura Y (2016) Anti-inflammatory action of green tea. Antiinflamm Antiallergy Agents Med Chem 15:74–90. doi:10.2174/1871523015666160915154443.
13. Fajardo AM and Piazza GA (2015) Anti-inflammatory approaches for colorectal cancer chemoprevention. Am J Physiol Gastrointest Liver Physiol 309:G59–G70. doi:10.1152/ajpgi.00101.2014.
14. Lee SJ, Lee IS and Mar W (2003) Inhibition of inducible nitric oxide synthase and cyclooxygenase-2 activity by 1,2,3,4,6-penta-O-galloyl-beta-D-glucose in murine macrophage cells. Arch Pharm Res 26:832–839. doi:10.1007/BF02980029.
15. Fang MZ, Wang Y, Ai N, Hou Z, Sun Y, Lu H, Welsh W and Yang CS (2003) Tea polyphe
    

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