Green Tea

Green tea is also known as Chinese tea and Japanese tea. Fresh leaves from the Camellia Sinensis plant are steamed to produce green tea.


Green Sampler


What It Is Used For
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.

How It Is Used
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.


What the Science Says
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.

NCCAM is supporting studies to learn more about the components in green tea and their effects on conditions such as cancer, diabetes, and heart disease.

Side Effects and Cautions

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. Caffeine can also raise blood pressure, and in very high doses, it can cause seizures, delirium, or irregular heart rhythms.

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 herb or dietary supplement you are using, including green tea. This helps to ensure safe and coordinated care.


Sources
National Cancer Institute. Tea and Cancer Prevention. National Cancer Institute Web site. Accessed May 1, 2006.
Green tea. Natural Medicines Comprehensive Database Web site. Accessed May 1, 2006.
Green tea (Camellia sinensis). Natural Standard Database Web site. Accessed May 1, 2006.

For More Information
Visit the NCCAM Web site and view:
"What's in the Bottle? An Introduction to Dietary Supplements"
"Herbal Supplements: Consider Safety, Too"

NCCAM ClearinghouseToll-free in the U.S.: 1-888-644-6226TTY (for deaf and hard-of-hearing callers): 1-866-464-3615E-mail: info@nccam.nih.gov
CAM on PubMedWeb site: nccam.nih.gov/camonpubmed/
NIH Office of Dietary SupplementsWeb site: ods.od.nih.gov

Never tried Green Tea? Then try the Green Sampler