Green Tea for Cancer Prevention

Because of the lower incidence of certain cancers in societies where green tea drinking is common (Japan, Korea, and China, for example), green tea has been studied in the laboratory for its preventive effects against experimental cancers. The results have universally shown that green tea can prevent many types of cancers in mice and rats.

Because of this finding, green tea has been examined for its content of cancer-reducing chemicals. The phytochemicals in green tea include catechins as well as the major chemical EGCG (epigallocatechin gallate). When experiments have been performed with this very active chemical, EGCG was shown to induce programmed cell death (apoptosis) in cancer cells growing in culture, and also reduce cancer cell growth in test tubes. It also was found to reduce growth receptors on cancer cells, so that cancer cells could not grow in response to chemicals that stimulate cancer cell reproduction.

But to further demonstrate the activity of green tea or green tea chemicals in people, in a recent article by Dr. M. Shimizu and co-workers from Gifu University in Japan (Cancer Epidemiology Biomarkers and Prevention, Volume 17, page 3020, 2008), doctors tested green tea extracts in the prevention of pre-cancerous growths in the colon and rectum. They studied 136 patients who had a prior growth (polyp or adenoma) removed at colonoscopy, and were still free of polyps one year later. Then, physicians randomly gave these individuals either continuation of usual habits, or supplementation with additional green tea extract. The patients then had a repeat colonoscopy 12 months later to determine how many pre-cancerous colon polyps had developed.

In patients who had received additional green tea extract, there was a 51 percent reduction in the number of pre-cancerous adenomas in just 12 months. In addition, compared to the group that had no additional green tea extract, the size of these pre-cancerous growths that were detected were much smaller if patients had received green tea extract. The degree of reduction in size was from 4.0 mm with usual diet and activities down to 3.0 mm with green tea extract.

How do we prevent colon cancer now?  The most important step is to remove these precancerous polyps before they develop into an invasive cancer. This is done by having a colonoscopy periodically, starting at age 50, or at a younger age if your family history suggests this is safer.

If you are at risk of having a colon cancer or polyp (or have had one in the past), and especially if you have a family history of colon or rectal cancer, colon polyps or rectal polyps, you should be taking steps to prevent the development of colorectal cancer by changing your diet to a more prudent diet, which consists of less red meat, more chicken and fish, at least five helpings of fruits, fruit juices, or vegetables daily and increased fiber). In addition, aspirin (at least one adult size aspirin daily provided there are no medical contraindications), calcium, and perhaps selenium are helpful in reducing colorectal adenomas and cancers.

But now the results of this study suggest that in addition, you should be discussing with your physician adding green tea or green tea extracts to further reduce the risk of cancer.

It is important to realize that the use of nutritional approaches to reduce cancer is still only partially proven. Additional studies are necessary to determine exactly which nutrients and which doses are most effective in preventing cancer. For certain nutritional approaches, such as green tea, there is abundant information available to help us understand its possible use in prevention of cancer. For other nutrients, there is less supportive evidence and their use is much more controversial.