Green tea is a good source of antioxidants called polyphenols, which may protect against cancer and heart disease, according to MedlinePlus. Green tea also improves mental alertness because of its caffeine content. Some people may use the tea to lose weight, but there is insufficient evidence to support its effectiveness.
Green tea is prepared from the unfermented leaves of the Camellia sinensis plant. This tea can be used in beverage or extract form. Although green tea is safe in most cases, more than 5 cups of green tea per day may cause headaches, dizziness and confusion because of the caffeine, according to MedlinePlus. Green tea may also interact with medications, such as adenosine, cimetidine and anticoagulant medications.