Skip to main content

Tea

Green tea leaves
© Steven Foster

Latin Names: Camellia sinensis

All types of tea—green, black, oolong, and white—are produced from the Camellia sinensis plant using different methods. Tea is usually brewed and drunk as a beverage, but green tea extracts are also sold in capsules and sometimes used in skin products. (Herbal teas are made from plants other than Camellia sinensis.) 

Tea contains various components, including polyphenols, alkaloids (caffeine, theophylline, and theobromine), amino acids, carbohydrates, proteins, chlorophyll, volatile organic compounds (chemicals that readily produce vapors and contribute to the aroma of tea), fluoride, aluminum, minerals, and trace elements. The polyphenols are thought to be responsible for the health benefits that have traditionally been attributed to tea, especially green tea. 

Green tea is often promoted for improving mental alertness, relieving digestive symptoms and headaches, and stimulating weight loss. Also, green tea and its extracts have been studied for their possible protective effects against heart disease and cancer. 

So far, we have learned the following about tea: 

  • Although tea and/or tea polyphenols have been found in animal studies to inhibit the growth of tumors in different parts of the body, the results of human studies—both epidemiologic and clinical studies—have been inconclusive.  
  • Green tea has not been shown to be effective for weight loss.  
  • Very few long-term studies have looked at 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.

For More Information

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

Telecommunications relay service (TRS): 7-1-1

Website: https://nccih.nih.gov/

Email: info@nccih.nih.gov (link sends email)

Know the Science

NCCIH and the National Institutes of Health (NIH) provide tools to help you understand the basics and terminology of scientific research so you can make well-informed decisions about your health. Know the Science features a variety of materials, including interactive modules, quizzes, and videos, as well as links to informative content from Federal resources designed to help consumers make sense of health information.

Explaining How Research Works (NIH)

Know the Science: 9 Questions To Help You Make Sense of Health Research

Understanding Clinical Studies (NIH)

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.

Website: https://pubmed.ncbi.nlm.nih.gov/

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 health care provider(s). 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.

Last Updated: February 2020