Of all the various foods and supplements that have been touted by conventional wisdom as having special health benefits, green tea is one where conventional wisdom got it right. If nothing else, it comes loaded with antioxidants, which are known to reduce inflammation and help boost immune function.
Studies have also demonstrated that green tea has the potential to reduce the risk of cancer and stroke and improve glucose tolerance. Drinking lots of green tea is always recommended, but you really have to drink excessive amounts of it in order to get the same benefits you would get from green tea extract.
Regardless of whether you go with the extract or the original drink, green tea can be extremely beneficial in preventing a number of chronic health issues, but there is insufficient evidence that it can cure an already-existing condition.
Mark Sisson gave five excellent reasons to drink green tea.