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Green Tea

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This fact sheet provides basic information about green tea—common names, usefulness and safety, and resources for more information.

 

Common Name:  green tea

Latin Name: 
Camellia sinensis

Background

  • Green, black, and oolong teas all come from the same plant, Camellia sinensis, but are prepared using different methods. To produce green tea, fresh leaves from the plant are lightly steamed.
  • Tea has been used for medicinal purposes in China and Japan for thousands of years.
  • Current uses of green tea as a beverage or dietary supplement include improving mental alertness, relieving digestive symptoms and headaches, and promoting weight loss. Green tea and its extracts, such as one of its components, EGCG, have been studied for their possible protective effects against heart disease and cancer.
  • Green tea is consumed as a beverage. It is also sold in liquid extracts, capsules, and tablets and is sometimes used in topical products (intended to be applied to the skin).

How Much Do We Know?

  • Although many studies have been done on green tea and its extracts, definite conclusions cannot yet be reached on whether green tea is helpful for most of the purposes for which it is used.

What Have We Learned?

  • There’s evidence that green tea enhances mental alertness, as would be expected because of its caffeine content.
  • The U.S. Food and Drug Administration has approved a specific green tea extract ointment as a prescription drug for treating genital warts.
  • Studies of green tea and cancer in people have had inconsistent results. The National Cancer Institute does not recommend for or against using green tea to reduce the risk of any type of cancer.
  • Very few long-term studies have investigated the effects of tea on heart disease risk. However, the limited evidence currently available suggests that both green and black tea might have beneficial effects on some heart disease risk factors, including blood pressure and cholesterol.
  • Green tea extracts haven’t been shown to produce a meaningful weight loss in overweight or obese adults. They also haven’t been shown to help people maintain a weight loss.
  • The National Center for Complementary and Integrative Health (NCCIH) is funding research on green tea and its extracts, including studies of the effects of high doses of tea components on the liver, whether substances in green tea can be helpful for iron overload disease, and the safety of a component of green tea in people who are HIV-positive.

What Do We Know About Safety?

  • Green tea, when consumed as a beverage, is believed to be safe when used in moderate amounts.
  • Liver problems have been reported in a small number of people who took concentrated green tea extracts. Although the evidence that the green tea products caused the liver problems is not conclusive, experts suggest that concentrated green tea extracts be taken with food and that people discontinue use and consult a health care provider if they have a liver disorder or develop symptoms of liver trouble, such as abdominal pain, dark urine, or jaundice.
  • Except for decaffeinated green tea products, green tea and green tea extracts contain substantial amounts of caffeine. Too much caffeine can make people feel jittery and shaky; interfere with sleep; and cause headaches.
  • Green tea has been shown to reduce blood levels (and therefore the effectiveness) of the drug nadolol, a beta-blocker used for high blood pressure and heart problems. It may also interact with other medicines.

Keep in Mind

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

NCCIH Clearinghouse

The NCCIH Clearinghouse provides information on NCCIH and complementary and integrative health approaches, including publications and searches of Federal databases of scientific and medical literature. The Clearinghouse does not provide medical advice, treatment recommendations, or referrals to practitioners.

Toll-free in the U.S.: 
1-888-644-6226
TTY (for deaf and hard-of-hearing callers): 
1-866-464-3615
E-mail: 

PubMed®

A service of the National Library of Medicine, PubMed® contains publication information and (in most cases) brief summaries of articles from scientific and medical journals. For guidance from NCCIH on using PubMed, see How To Find Information About Complementary Health Approaches on PubMed.

Office of Dietary Supplements (ODS), National Institutes of Health (NIH)

ODS seeks to strengthen knowledge and understanding of dietary supplements by evaluating scientific information, supporting research, sharing research results, and educating the public. Its resources include publications (such as Dietary Supplements: What You Need to Know), fact sheets on a variety of specific supplement ingredients and products (such as vitamin D and multivitamin/mineral supplements), and the PubMed Dietary Supplement Subset.

E-mail: 

Key References

This publication is not copyrighted and is in the public domain. Duplication is encouraged.

NCCIH has provided this material for your information. It is not intended to substitute for the medical expertise and advice of your primary health care provider. We encourage you to discuss any decisions about treatment or care with your health care provider. The mention of any product, service, or therapy is not an endorsement by NCCIH.
NCCIH Publication No.: 
D273
Updated: 
September 2016

This publication is not copyrighted and is in the public domain. Duplication is encouraged.


NCCIH has provided this material for your information. It is not intended to substitute for the medical expertise and advise of your primary health care provider. We encourage you to discuss any decisions about treatment or care with your health care provider. The mention of any product, service, or therapy is not an endorsement by NCCIH.


U.S. Department of Health & Human Services, National Institutes of Health, National Center for Complementary and Integrative Health

nccih.nih.gov

This page last modified November 30, 2016