Manataka American Indian Council









The Mystery of Green Tea Solved


This basic information about green tea, uses, potential side effects, and resources will help resolve some of the mystery about green tea. All types of tea (green, black, and oolong) are produced from the Camellia sinensis plant using different methods. Fresh leaves from the Camellia sinensis plant are steamed to produce green tea.  The common names for green tea are: Chinese tea, Japanese tea. 


Green tea and green tea extracts, such as its component EGCG, have been used to prevent and treat a variety of cancers, including breast, stomach, and skin cancers.


Green tea and green tea extracts have also been used for improving mental alertness, aiding in weight loss, lowering cholesterol levels, and protecting skin from sun damage.


Green tea is usually brewed and drunk as a beverage. Green tea extracts can be taken in capsules and are sometimes used in skin products.


Laboratory studies suggest that green tea may help protect against or slow the growth of certain cancers, but studies in people have shown mixed results.


Some evidence suggests that the use of green tea preparations improves mental alertness, most likely because of its caffeine content. There are not enough reliable data to determine whether green tea can aid in weight loss, lower blood cholesterol levels, or protect the skin from sun damage.


The National Center for Complimentary and Alternative Medicine Clearinghouse is supporting studies to learn more about the components in green tea and their effects on conditions such as cancer, diabetes, and heart disease.


Green tea is safe for most adults when used in moderate amounts. Green tea and green tea extracts contain caffeine. Caffeine can cause insomnia, anxiety, irritability, upset stomach, nausea, diarrhea, or frequent urination in some people.

Green tea contains small amounts of vitamin K, which can make anticoagulant drugs, such as warfarin, less effective.


Tell your health care providers about any complementary and alternative practices you use. Give them a full picture of what you do to manage your health. This will help ensure coordinated and safe care.



National Cancer Institute. Tea and Cancer Prevention. National Cancer Institute

Green tea. Natural Medicines Comprehensive Database Web site.

Green tea (Camellia sinensis). Natural Standard Database Web site.

NIH National Library of Medicine's MedlinePlus
Green Tea Listing:


More Information:

What's in the Bottle? An Introduction to Dietary Supplements

Herbal Supplements: Consider Safety, Too

National Center for Complimentary and Alternative Medicine Clearinghouse 1-1-888-644-6226
TTY (for deaf and hard-of-hearing callers): 1-866-464-3615
Web site:




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