Green tea is made from the leaves of the Camellia sinesis, a plant native to parts of Asia. It has been a popular drink in that part of the world for many years and is gaining popularity here in the West.
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| Green Tea Photo © Pam Stephan |
Antioxidants and Free Radicals
Green tea's cancer-fighting reputation comes from its polyphenols, chemicals that have antioxidant properties. Antioxidants protect the cells in your body from free radicals, highly reactive molecules that speed the damage caused by chemicals in the environment or aging, which can lead to the development of cancer. Other examples of antioxidants include lycopene, found in cooked tomatoes, and vitamin A, found in carrots.
What Do the Antioxidants in Green Tea Do?
One of the antioxidants found almost exclusively in green tea is epigallocatechin-3-gallate (EGCG), which has been at the heart of recent green tea headlines. Overall, research has yielded conflicting results on whether green tea can fight or prevent cancer.
However, one particularly interesting study, presented at a medical conference in 2008, has shown promising results. Researchers at the University of Mississippi Medical Center added EGCG to the drinking water of 10 female mice. An equal number were given plain drinking water. All were later injected with breast cancer cells. In the mice that had ingested EGCG, tumors were 66% smaller than those in the untreated mice. Their tumors also appeared to have less blood supply, suggesting that the EGCG works by inhibiting blood supply to cancer cells.
While green tea has been the subject of other studies, most of these have focused on whether it prevents cancer (among lifelong tea drinkers in Asia, for example), not whether it slows an existing disease process. Results have been mixed, but more controlled and randomized studies on humans are currently in the works.
What Does this Study Mean for Me?
First, it's important to note that the amount of EGCG these mice were given translates to an awful lot of tea for the average human, that is, about 15 to 30 cups each day for 5 weeks. Although that may not be a pace you can keep up with, there's little harm in adding a few cups of green tea to your daily routine.
Aside from its cancer-fighting potential, there is some evidence that green tea lowers cholesterol and improves function of the immune system. In a 2007 study, researchers at the University of Michigan Health System found that EGCG inhibits production of molecules in the immune system that are blamed for inflammation and joint damage in arthritis sufferers.
As its popularity grows in the Western world, green tea is getting easier to find; if it's not on the shelf at your local supermarket, check with a nearby health food store or Asian market.
Green tea does contain caffeine. Be on the lookout for potential side effects, such as heart palpitations and nervousness, and adjust consumption as needed.
Sources:
Ahmed, Salah-uddin. "Epigallocatechin-3-gallate Inhibits IL-1-Induced IL-6 Production and Cyclooxygenase-2 Expression in Rheumatoid Arthritis Synovial Fibroblasts in Vitro." Experimental Biology 2007. 120th Annual Meeting of the American Physiological Society, Washington, D.C. 29 Apr 2007.
American Cancer Society Staff, "Green Tea." Cancer.org. 29 Jun 2007. American Cancer Society. 30 Apr .2008.
Gu, Jian-Wu. "Oral Administration of EGCG, an Antioxidant Found in Green Tea, Inhibits Tumor Angiogenesis and Growth of Breast Cancer in Female Mice." Experimental Biology 2008. 121st Annual Meeting of the American Physiological Society, San Diego , Calif. 7 Apr 2008.
NIH staff, "Antioxidants." MedlinePlus: Antioxidants. 15 Apr. 2008. National Institutes of Health. 3 May 2008.
NIH staff, "Free Radicals" Genetics Home Reference. 25 Apr. 2008. National Institutes of Health. 3 May 2008.
