Green Tea and Cancer

Tuesday, January 9, 2007 - 4:13pm

By Dena McDowell, MS, RD

Teas have been used for thousands of years for healing properties of different disease states. Green tea, which is commonly consumed in Asia, may have anticancer properties. Researchers are studying the effects of green tea on various health conditions but have found promising results for certain forms of cancer. Read on to learn about how green tea can help fight cancer.

The history of green tea
Green tea comes from the leaves of the Camellia sinensis plant and has been used in ancient Chinese medicine for more than 5000 years. Unlike black tea, green tea is produced by lightly steaming the freshly cut leaves. Black tea is created after the leaves have fermented and oxidized. The process of making green tea only allows for minimal oxidation therefore the antioxidants and phytochemicals are retained in higher amounts than in black tea. Green tea contains large amounts of catechins and polyphenols which are chemicals that prevent free radical damage in the cells. Free radical damage is partly responsible for creating cancerous cells. Green tea contains almost three times the amount of catechins when compared to black tea.

What has green tea been used for?
Throughout history green tea has been used for various disease conditions. According to the American Cancer Society green tea has been used to treat adenocarinomas, bladder cancer, liver cancer, kidney cancer, leukemia, oral leukoplakia, ovarian cancer, breast cancer, prostate cancer, cancers of the digestive tract and bone marrow diseases. Other non-cancer conditions that green tea has been for are: detoxification from alcohol or other drugs, cognitive performance enhancement, Chron’s disease, gastritis, diabetes, diarrhea, headaches, heart disease, HIV/AIDS, Parkinson’s disease, stroke prevention and joint pain. Research is unclear if all of these maladies will benefit from green tea.

What the research tells us for cancer prevention
Several observational studies have been done to determine if green tea consumption affects cancer incidence. Research has found that those who drink green tea regularly may have a reduced risk of developing stomach, colon, rectal, pancreas, prostate, cervical, ovarian, breast and esophageal cancer. Although the results are promising the researchers noted that other lifestyle factors may also play a part in reducing participant’s risk of cancer development. An another study looking at people who smoke cigarettes found that drinking an average of four cups of decaffeinated green tea a day reduced damage to DNA which may also reduce cancerous cells from developing.

Animal studies have shown that catechins or polyphenols in green tea may help reduce cancer cell growth. Other early studies have shown an antiestrogenic effect with large amounts of green tea (four cups a day) in estrogen receptor positive breast cancer. More research needs to be done to determine the actual relationship.

Dosage and safety of green tea
An actual dose of green tea for cancer prevention has not been determined as more research needs to be done. Green tea comes in either a brewed form or capsule form. One cup (8 ounces) contains between 80-100 milligrams of polyphenols. Studies have looked at anywhere from one to ten cups of green tea a day for anticancer properties. It should be noted that to get the maximum anticancer benefit from drinking green tea you need to drink the brewed form of the tea (either hot or iced). Drinking tea flavored beverages do not contain the polyphenol content and will not help play a role in cancer prevention.

In the capsule form, Green Tea Extract (GTE) varies widely by manufacturer. Typical doses are anywhere from 100-175 milligrams per capsule. And the polyphenol content may also vary from 60-97 percent meaning that not all capsules are alike. Early research shows promising benefits of 360 milligrams a day of GTE however more research needs to be done to determine an actual dose.

Green tea in either the brewed or capsule form contains caffeine which acts as a stimulant and diuretic. Caffeine containing beverages may also increase stomach acid production and may worsen gastrointestinal ulcers. Green tea also contains tannins which may cause constipation in some and act as a trigger for migraine sufferers. Large doses of caffeine (250 or greater) may increase blood pressure and heart rate. Diabetics should be cautious in using green tea as it may alter blood sugars and cause hypoglycemia in large doses. Green tea also contains vitamin K which may interact with blood thinners. Inform your medical doctor if using green tea.

More research needs to be done to pinpoint the exact mechanism of how the components in green tea help reduce cancer cells from growing but preliminary results are promising. Although the dosage has not been established drinking moderate amounts of green tea is safe and may potentially reduce your risk of developing certain forms of cancer. If you are sensitive to caffeine try decaffeinated tea instead. Also if taking the capsule form or large quantities of brewed green tea inform your healthcare provider to make sure it will not interact with any coexisting medical conditions.