GREEN TEA

Introduction

This fact sheet provides basic information about green tea--common names, uses, potential side effects, and resources for more information. 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.

Common Names--green tea, Chinese tea, Japanese tea

Latin Names--Camellia sinensis

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 herbA plant or part of a plant used for its flavor, scent, or potential therapeutic properties. Includes flowers, leaves, bark, fruit, seeds, stems, and roots. or dietary supplementA product that contains vitamins, minerals, herbs or other botanicals, amino acids, enzymes, and/or other ingredients intended to supplement the diet. The U.S. Food and Drug Administration has special labeling requirements for dietary supplements and treats them as foods, not drugs. 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.