Green Tea

Green tea is made from the dried leaves of the same plant as traditional tea. However, traditional tea leaves are fermented, and green tea leaves are steamed but unfermented. Green tea may be brewed and drunk or ingested in tablet or capsule form. Green tea contains caffeine, but many extracts have been decaffeinated. It is high in flavonoids, polyphenols, and catechins. Those substances are antioxidants Antioxidants The human body needs various vitamins and minerals in order to thrive. Many of these nutrients can be found in whole, non-processed foods such as fruits and vegetables. However, most modern... read more , often thought to protect cells from damage by oxygen, mutations, and cancer.

(See also Overview of Dietary Supplements Overview of Dietary Supplements Dietary supplements are used by about 75% of Americans. They are the most common therapies included among integrative medicine and health (IMH) and complementary and alternative medicine (CAM)... read more .)

People take green tea for many reasons, including prevention of cancer and coronary artery disease Overview of Coronary Artery Disease (CAD) Coronary artery disease is a condition in which the blood supply to the heart muscle is partially or completely blocked. The heart muscle needs a constant supply of oxygen-rich blood. The coronary... read more , as well as treatment of external genital warts Human Papillomavirus (HPV) Infection Human papillomavirus (HPV) can be sexually transmitted and causes changes in cells, which can lead to genital warts or to precancer or cancer of the cervix, vagina, vulva, anus, or throat. Different... read more . Other reasons are reduction of fat (lipid) levels in the blood, relief of osteoarthritis pain and menopausal symptoms, and enhancement of weight loss, memory, and longevity.

Few of the benefits claimed for green tea are supported by strong scientific evidence. However, topical (applied directly on the wart) green tea may help treat genital warts. Studies have also shown a small but significant loss of weight among users.

Side effects are related to the effects (including the dose) of caffeine. They include insomnia, anxiety, rapid heart rate (tachycardia), and mild tremor. Pregnant women should avoid excessive amounts due to the caffeine content, because of the risk of miscarriage. Rare case reports document liver toxicity.

Vitamin K in green tea may decrease anticoagulant effects of warfarin, thus increasing the risk of blood clots. Green tea may cause increased side effects (due to its caffeine) if combined with amphetamines or supplements that are stimulants, particularly ephedra and bitter orange. When combined with MAO inhibitors, blood pressure and heart rate may increase. Green tea may greatly decrease blood levels of nadolol, a beta blocker, as well as atorvastatin. Green tea may also decrease absorption of iron and folic acid.

Green tea is generally considered safe, although the health benefits, if any, are likely small. People should avoid drinking large amounts, especially if pregnant.