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Green Tea (Camellia sinensis)

Green Tea (Camellia sinensis)

*This statement has not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.  

About

Green tea is made from the Camellia sinensis plant. The dried leaves and leaf buds of Camellia sinensis are used to produce various types of teas. Green tea is prepared by steaming and pan-frying these leaves and then drying them. Other teas such as black tea and oolong tea involve processes in which the leaves are fermented (black tea) or partially fermented (oolong tea).

Green tea is taken by mouth to improve mental alertness and thinking.

It is also taken by mouth for depression, non-alcoholic fatty liver disease (NAFLD), inflammatory bowel disease (ulcerative colitis or Crohn's disease), weight loss and to treat stomach disorders, vomiting, diarrhea, headaches, and bone loss (osteoporosis).

Some people take green tea by mouth to prevent various cancers. Some women use green tea to fight human papilloma virus (HPV), which can cause genital warts, the growth of abnormal cells in the cervix (cervical dysplasia), and cervical cancer.

Green tea is also taken by mouth for Parkinson's disease, diseases of the heart and blood vessels, diabetes, low blood pressure, chronic fatigue syndrome (CFS), dental cavities (caries), kidney stones, and skin damage.

Instead of drinking green tea, some people apply green tea bags to their skin to soothe sunburn and prevent skin cancer due to sun exposure. Green tea bags are also used to decrease puffiness under the eyes, as a compress for tired eyes or headache, and to stop gums from bleeding after a tooth is pulled. A green tea footbath is used for athlete's foot.

Some people gargle with green tea to prevent colds and flu. Green tea extract is also used in mouthwash to reduce pain after tooth removal. Green tea in candy is used for gum disease.

Green tea is used in an ointment for genital warts.

In food, people drink green tea as a beverage

How does it work?

The useful parts of green tea are the leaf bud, leaf, and stem. Green tea is not fermented and is produced by steaming fresh leaves at high temperatures. During this process, it is able to maintain important molecules called polyphenols, which seem to be responsible for many of the benefits of green tea.

Polyphenols might be able to prevent inflammation and swelling, protect cartilage between the bones, and lessen joint degeneration. They also seem to be able to fight human papilloma virus (HPV) infections and reduce the growth of abnormal cells in the cervix (cervical dysplasia). Research cannot yet explain how this works.

Green tea contains 2% to 4% caffeine, which affects thinking and alertness, increases urine output, and may improve the function of brain messengers important in Parkinson's disease. Caffeine is thought to stimulate the nervous system, heart, and muscles by increasing the release of certain chemicals in the brain called "neurotransmitters."

Antioxidants and other substances in green tea might help protect the heart and blood vessels.

Traditionally used for

Genital warts.
High cholesterol.
Abnormal development of cells of the cervix (cervical dysplasia).
Clogged arteries (coronary artery disease).
High blood pressure.
Low blood pressure.
Thick, white patches on the gums (oral leukoplakia).
Osteoporosis.
Parkinson's disease.
Acne.
Abnormal protein buildup in the organs (Amyloidosis).
Athletic performance.
Heart disease.
Colds and flu.
Depression.
Diabetes.
Fertility problems.
Allergy to Japanese cedar (pollinosis).
Leukemia.
Mental alertness.
Metabolic syndrome.
Nonalcoholic fatty liver disease (NAFLD).
Obesity.
Gum disease (periodontal disease).
Pneumonia.
Pain after surgery.
Stress.
Stroke.
Athlete's foot.
Inflammatory bowel disease (ulcerative colitis).
Upper respiratory tract infection.
Wrinkled skin.

Dosage

By mouth

For high cholesterol: Green tea or green tea extracts containing 150 to 2500 mg catechins, taken in single or 2 divided doses daily for up to 24 weeks, has been used.

For abnormal development of cells of the cervix (cervical dysplasia): 200 mg of green tea extract, taken by mouth daily along with a green tea ointment applied twice weekly for 8-12 weeks, has been used.

For high blood pressure: A green tea drink, made by boiling a 3 gram tea bag with 150 mL water, has been used three times daily about 2 hours after each meal for 4 weeks. Also, 379 mg of a specific product containing green tea extract (Olimp Labs, Debica, Poland), taken daily with the morning meal for 3 months, has been used.

For low blood pressure: 400 mL of green tea taken before lunch has been used.

For thick, white patches on the gums (oral leukoplakia): 3 grams of mixed green tea taken by mouth and applied to the skin for 6 months has been used.

For osteoporosis: Capsules containing 500 mg of green tea polyphenols, taken twice daily alone or while practicing tai chi for 60 minutes three times weekly for 24 weeks, has been used.

By skin

For genital warts: A specific green tea extract ointment (Veregen, Bradley Pharmaceuticals; Polyphenon E ointment 15%, MediGene AG) applied three times daily to warts for up to 16 weeks, has been used. This product is FDA-approved for treating this condition.

For abnormal development of cells of the cervix (cervical dysplasia): A green tea ointment has been used alone twice weekly, or in combination with 200 mg of green tea extract taken by mouth daily for 8-12 weeks.

For thick, white patches on the gums (oral leukoplakia): 3 grams of mixed green tea taken by mouth and applied to the skin for 6 months has been used.

Possible Side Effects

Green tea is SAFE for most adults when consumed as a drink in moderate amounts or when green tea extract is applied to the skin as a specific ointment (Veregen, Bradley Pharmaceuticals), short-term. Green tea extract is SAFE for most people when taken by mouth for up to 2 years, when applied to the skin as other ointments short-term, or when used as a mouthwash short-term. In some people, green tea can cause stomach upset and constipation. Green tea extracts have been reported to cause liver and kidney problems in rare cases.

Green tea is POSSIBLY UNSAFE when taken by mouth long-term or in high-doses. It can cause side effects because of the caffeine. These side effects can range from mild to serious and include headache, nervousness, sleep problems, vomiting, diarrhea, irritability, irregular heartbeat, tremor, heartburn, dizziness, ringing in the ears, convulsions, and confusion. Green tea seems to reduce the absorption of iron from food. Drinking very high doses of green tea is LIKELY UNSAFE and can actually be fatal. The fatal dose of caffeine in green tea is estimated to be 10-14 grams (150-200 mg per kilogram). Serious toxicity can occur at lower doses.

Special Precautions & Warnings

Children: Green tea is SAFE for children when used in amounts commonly found in foods and beverages or when used for gargling three times daily for up to 90 days.

Pregnancy and breast-feeding: If you are pregnant or breast-feeding, green tea in small amounts - about 2 cups per day - is POSSIBLY SAFE. This amount of green tea provides about 200 mg of caffeine. However, drinking more than 2 cups of green tea per day is POSSIBLY UNSAFE. Consuming more than 2 cups of green tea daily has been linked to an increased risk of miscarriage and other negative effects due to the caffeine content. Also, green tea might increase the risk of birth defects associated with folic acid deficiency. In women who are nursing, caffeine passes into breast milk and can affect a nursing infant. Don't drink an excessive amount of green tea if you are pregnant or breast-feeding.

"Tired blood" (anemia): Drinking green tea may make anemia worse.

Anxiety disorders: The caffeine in green tea might make anxiety worse.

Bleeding disorders: Caffeine in green tea might increase the risk of bleeding. Don't drink green tea if you have a bleeding disorder.
Heart conditions: Caffeine in green tea might cause irregular heartbeat.

Diabetes: Caffeine in green tea might affect blood sugar control. If you drink green tea and have diabetes, monitor your blood sugar carefully.

Diarrhea: Green tea contains caffeine. The caffeine in green tea, especially when taken in large amounts, can worsen diarrhea.

Glaucoma: Drinking green tea increases pressure inside the eye. The increase occurs within 30 minutes and lasts for at least 90 minutes.

High blood pressure: The caffeine in green tea might increase blood pressure in people with high blood pressure. However, this does not seem to occur in people who regularly drink green tea or other products that contain caffeine.

Irritable bowel syndrome (IBS): Green tea contains caffeine. The caffeine in green tea, especially when taken in large amounts, can worsen diarrhea and might worsen symptoms of IBS.

Liver disease: Green tea extract supplements have been linked to several cases of liver damage. Green tea extracts might make liver disease worse.

Weak bones (osteoporosis): Drinking green tea can increase the amount of calcium that is flushed out in the urine. Caffeine should be limited to less than 300 mg per day (approximately 2-3 cups of green tea). It is possible to make up for some calcium loss caused by caffeine by taking calcium supplements.

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