Epigallocatechin, often referred to as EGCG, is a plant-based compound found in various foods and beverages. It belongs to a group of natural chemicals known as catechins, a type of flavonoid. EGCG is studied for its potential effects on human health.
Key Sources of Epigallocatechin
Green tea (Camellia sinensis) is the primary source of EGCG, with dried leaves containing up to 7380 mg per 100 grams. White tea also provides a notable amount (approximately 4245 mg per 100 grams). Black tea has significantly lower EGCG due to oxidation during production, which converts catechins into other compounds.
Beyond tea, EGCG is found in smaller quantities in other plant-based foods, including apples, berries, and some nuts. The method of preparing tea greatly influences EGCG extraction. Water temperatures between 70–80°C (158–176°F) are effective for extraction, as higher temperatures can lead to degradation.
Steeping time also plays a role, with EGCG extraction increasing up to about 5 minutes. Longer steeping times might extract more total catechins but can also release more tannins and caffeine, leading to a bitter taste. The quality of tea leaves, such as high-quality loose-leaf or matcha, also affects the initial EGCG concentration. Matcha, consumed as a powder, offers significantly higher EGCG concentrations.
Understanding Its Action in the Body
EGCG interacts with the human body primarily through its antioxidant and anti-inflammatory properties. It directly neutralizes reactive oxygen species (ROS), or free radicals, which are unstable molecules that can damage cells and contribute to chronic conditions. EGCG also chelates free transition metals, further reducing oxidative stress.
Beyond direct scavenging, EGCG exerts indirect antioxidant effects by influencing cellular pathways. It can inhibit pro-oxidant enzymes like inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2), which produce harmful molecules. EGCG also promotes the production of antioxidant enzymes, such as glutathione S-transferase and superoxide dismutase (SOD), by inducing the expression of proteins like Nrf2.
EGCG’s anti-inflammatory actions involve modulating signaling pathways within cells. It suppresses the activation of nuclear factor-kappa B (NF-κB), a protein complex regulating genes involved in inflammation and immune responses. By inhibiting NF-κB, EGCG can downregulate pro-inflammatory cytokines, such as IL-8 and TNF-α, and reduce the expression of adhesion molecules that contribute to inflammation.
Potential Health Applications
EGCG is being studied for its potential health applications. In cardiovascular health, EGCG may contribute to improved vascular function by increasing cyclic guanosine monophosphate (cGMP) levels, which can lead to vasodilation. Studies suggest that green tea consumption may help lower total cholesterol, low-density lipoprotein (LDL) cholesterol, and potentially reduce blood pressure.
Regarding metabolic support, EGCG is being investigated for regulating blood sugar levels and influencing lipid metabolism. Research indicates it may offer protective effects against obesity-related disorders such as atherosclerosis and diabetes. EGCG’s involvement in regulating apoptosis and cell cycle progression also makes it a candidate for managing metabolic diseases.
For neuroprotection, EGCG may safeguard neurons from damage and potentially enhance cognitive function. Its antioxidant capacity helps reduce reactive oxygen species generated during physiological stress in the brain. EGCG may also modulate signaling pathways important for neuronal survival and growth, and has been linked to a reduced risk of age-related brain decline, including Alzheimer’s and Parkinson’s diseases.
For skin health, EGCG exhibits anti-inflammatory and antioxidant effects. It can inhibit inflammation mediated by various cell types in the skin, including fibroblasts. Topical application of EGCG has been shown to potentially decrease UV-induced inflammation.
EGCG’s role in cancer research is explored, with preclinical evidence suggesting it may have chemopreventive effects against various malignancies. It has been shown to inhibit the growth, proliferation, and metastasis of cancer cell lines. EGCG’s anticancer mechanisms include influencing cell signaling pathways, promoting programmed cell death (apoptosis), and inhibiting DNA hypermethylation.
Consumption Guidance and Safety
The amount of EGCG in brewed green tea can vary, but a typical 240 milliliter (ml) serving may provide around 187 mg. Health experts often suggest drinking 2-3 cups of high-quality green tea daily to maximize the benefits of its catechins.
When considering EGCG supplements, exercise caution. While EGCG from whole food sources like green tea is generally considered safe, concentrated supplements can pose risks. Some reports suggest that very high doses of EGCG may lead to liver toxicity in animals and humans.
A tolerable upper intake level of 300 mg EGCG per day has been proposed for food supplements, with liver effects generally not observed below 600 mg per day. Possible side effects from high supplement doses include liver and kidney failure, dizziness, low blood sugar, and anemia. Consult a healthcare professional before taking EGCG supplements, especially if pregnant or taking other medications.
EGCG may interact with certain medications. For instance, it might reduce the effectiveness of beta-blockers like nadolol, used for high blood pressure, and could affect the absorption of statins such as atorvastatin. Patients taking medications like clozapine, digoxin, or warfarin should avoid EGCG extracts and supplements.