Epigallocatechin gallate (EGCG) is an active compound found in green tea. This plant-derived substance is a type of polyphenol called a catechin. Scientific interest in EGCG focuses on its potential health benefits, particularly its role in cancer research, exploring how it interacts with cancer cells and influences disease progression.
Where EGCG is Found
Green tea, from the Camellia sinensis plant, is the most abundant dietary source of EGCG. Its concentration varies based on brewing temperature and steeping time. EGCG is also present in smaller amounts in other foods and beverages, including black tea, white tea, coffee, red wine, grapes, and various berries like strawberries and raspberries. Trace amounts are found in apple skin, plums, onions, hazelnuts, pecans, and dark chocolate.
How EGCG May Affect Cancer Cells
EGCG may influence cancer cells through several biological pathways. One mechanism involves inducing programmed cell death (apoptosis), triggering cancer cells to self-destruct without harming healthy cells. EGCG may also interfere with the uncontrolled multiplication of cancer cells, limiting their growth and spread.
Another area of interest is EGCG’s potential to inhibit angiogenesis, the formation of new blood vessels tumors need to grow and spread. EGCG has been observed to reduce the expression of vascular endothelial growth factor (VEGF), a protein promoting blood vessel formation. The compound also exhibits antioxidant and anti-inflammatory properties, which may protect cells from damage by unstable molecules called free radicals. EGCG can modulate various cellular signaling pathways, including those involved in cell proliferation and inflammation, such as NF-κB, PI3K/AKT, and MAPK/ERK.
Research Findings on EGCG and Cancer
Investigations into EGCG’s effects on cancer have progressed from laboratory experiments to human trials. Much promising evidence comes from preclinical studies using cancer cell lines (in vitro) and animal models (in vivo). These studies have shown EGCG’s ability to affect cancer cells by triggering cell death, limiting growth, and inhibiting blood vessel formation across various cancer types, including prostate, colorectal, lung, and oral cancers. For instance, EGCG reduced breast cancer xenograft growth in mice by suppressing glucose metabolism.
Human studies and clinical trials, however, have yielded mixed results and are often in early stages. Some research suggests EGCG, when combined with certain chemotherapy drugs, might increase tumor cell sensitivity to treatment or help reduce chemotherapy side effects. However, EGCG’s efficacy in human brain tumor patients, for example, when combined with drugs like temozolomide, has not been definitively confirmed. Epidemiological studies have explored associations between regular green tea consumption and reduced cancer incidence, such as a possible link to lower breast cancer risk.
Findings from laboratory and animal studies do not always translate directly to humans. While preclinical research indicates potential anti-cancer actions, larger human clinical trials are needed to confirm these benefits and establish EGCG as a reliable cancer preventative or treatment. The current human evidence is not strong enough to make definitive claims about EGCG’s effectiveness in preventing or treating cancer.
Important Considerations When Using EGCG
While EGCG offers potential health benefits, important considerations exist, especially when consumed in concentrated forms like supplements. A notable concern is the risk of liver injury (hepatotoxicity), particularly with high doses of EGCG extracts. Daily intakes of 800 mg or more from supplements may increase liver damage risk. This risk might be heightened when EGCG is consumed on an empty stomach or during dieting or fasting, as these conditions can affect the liver’s ability to process the compound.
EGCG can also interact with certain medications. Its antioxidant properties might theoretically reduce the effectiveness of some chemotherapy drugs. EGCG also has potential to interact with blood thinners or drugs like glyburide, used to lower blood sugar. Individuals taking medications should exercise caution and seek medical advice before considering EGCG supplementation.
EGCG content in supplements can be significantly higher than in a typical cup of green tea (70 to 187 mg). The amount also varies widely between different tea brands and preparation methods. EGCG supplements are not a substitute for conventional cancer treatments. Individuals with cancer or other health conditions should always consult a healthcare professional before incorporating EGCG into their routine.