Here's a fantastic review on green tea.

A Review on the Beneficial Effects of Tea Polyphenols on Human Health
www.researchgate.net/profile/Mohammad_Afzal14/publication/26557319_A_Review_on_the_Beneficial_Effects_of_Tea_Polyphenols_on_Human_Health/links/0deec53ba19126ecdb000000.pdf?inViewer=0&pdfJsDownload=0&origin=publication_detail