How Green Tea Extract Helps Protect Against Cancer
Tea is the most widely consumed beverage worldwide.[1] Tea, especially green tea, contains compounds called flavonoids that have antioxidant properties. Antioxidants are chemicals that protect your body against damage caused by free radicals. Free radicals are products that are formed in your body as a result of your body’s natural processes. Free radicals can also be formed if you are exposed to chemicals such as cigarette smoke or household chemicals. A few examples of free radicals include hydrogen peroxide and superoxide anion.[2]
Epigallocatechin-3-gallate, also known as EGCG, is one of the most important compounds found in green tea. EGCG has a role in many types of cancer including: breast, skin, lung, prostate, liver, colorectal, and pancreatic. The way that EGCG, and green tea extract as a whole, protects against certain types of cancers can vary but we will discuss a few mechanisms in detail.
In breast cancer, EGCG causes a downregulation of epidermal growth factor receptors (EGFR) and can decrease or inhibit various other chemicals including: MMP-2, FAK, nuclear factor-kappa B, and VEGF. Basically, cancer causes an increase in some chemicals which stimulates that cancer to grow even more. Green tea can decrease these chemicals to protect against the growth and the spread of cancer. And studies have shown that various chemicals in green tea play an important role against the spread of breast cancer cells.[3]
In liver cancer, EGCG can suppress the activities of MMP-2 and MMP-9 which suppresses the invasion and spreading of liver cancer cells. One study showed that EGCG strongly suppressed the proliferation (rapid growth in numbers) and spread of liver cancer cells.[4] Another ingredient in green tea, theanine, was actually studied in combination with a chemotherapy agent, doxorubicin, and it showed that the combination of the two helped more than the doxorubicin alone.[5]
For colorectal cancer, the second most deadly cancer in the US, EGCG has been shown to decrease metastasis signaling. EGCG decreased the amount of hydrogen peroxide generated by the body compared with the absence of EGCG. Large amounts of hydrogen peroxide were shown to directly increase metastasis.[6]There are also a few other ways by which EGCG exerts its’ anticancer activities including: increased MMP-7 and activation of ERK1/2, JNK1/2, and p38 expression.[7]
The spread of cancer, or metastasis, is responsible for the most deaths from cancer so scientists are always looking for ways to fight it. The amount of evidence showing green tea extract’s role in either fighting off cancer or preventing its’ spread is overwhelming already and is still increasing. There is a reason that even though Japan has a high rate of smoking, it also has a relatively low risk of lung cancer and that reason may be partially due to their heavy consumption of green tea.[8]
References:
- Khan N, Mukhtar H. Cancer and metastasis: prevention and treatment by green tea. Cancer metastasis reviews. 2010;29(3):435–445. doi:10.1007/s10555–010–9236–1.
- Lobo V, Patil A, Phatak A, Chandra N. Free radicals, antioxidants and functional foods: Impact on human health. Pharmacognosy Reviews. 2010;4(8):118–126. doi:10.4103/0973–7847.70902.
- Kushima Y, et al. Inhibitory effect of (−)-epigallocatechin and (−)-epigallocatechin gallate against heregulin beta1-induced migration/invasion of the MCF-7 breast carcinoma cell line. Biological & Pharmaceutical Bulletin. 2009;32(5):899–904.
- Wei DZ, et al. Inhibition of liver cancer cell proliferation and migration by a combination of (−)-epigallocatechin-3-gallate and ascorbic acid. Journal of Chemotherapy. 2003;15(6):591–595.
- Sugiyama T, Sadzuka Y. Combination of theanine with doxorubicin inhibits hepatic metastasis of M5076 ovarian sarcoma. Clinical Cancer Research. 1999;5(2):413–416.
- Larsen CA, Dashwood RH. Suppression of Met activation in human colon cancer cells treated with (−)-epigallocatechin-3-gallate: minor role of hydrogen peroxide. Biochemical and Biophysical Research Communications. 2009;389(3):527–530.
- Kim M, et al. (−)-Epigallocatechin-3-gallate promotes pro-matrix metalloproteinase-7 production via activation of the JNK1/2 pathway in HT-29 human colorectal cancer cells. Carcinogenesis. 2005;26(9):1553–1562.
- Funatogawa I, Funatogawa T, Yano E. Trends in smoking and lung cancer mortality in Japan, by birth cohort, 1949–2010. Bulletin of the World Health Organization. 2013;91(5):332–340. doi:10.2471/BLT.12.108092.
