Green tea is made from the dried leaves of the same plant as traditional tea, an evergreen shrub native to Asia. However, traditional tea leaves are fermented, and green tea leaves are steamed but unfermented. Green tea may be brewed and drunk or ingested in extracted tablet or capsule form. It has multiple components that are thought to have antioxidant and anticancer effects. Green tea contains polyphenols and catechins as well as caffeine, but many extracts have been decaffeinated.
Green tea is said to have multiple health benefits, none of which are supported by strong scientific evidence. It has been used for cancer prevention, weight loss, serum lipid reduction, prevention of coronary artery disease, memory enhancement, relief of osteoarthritis pain, treatment of menopausal symptoms, and longevity.
Adverse effects are related to effects of caffeine. They include insomnia, anxiety, tachycardia, and mild tremor. Pregnant women should avoid excessive caffeine.
Last full review/revision May 2009 by Ara DerMarderosian, PhD
Content last modified August 2013