How much green tea? Green tea is  good for you, but only if drunk in  moderation. While the polyphenols in  green tea are credited with  preventing heart disease and cancer, it  seems they can cause liver and  kidney damage if consumed in very large  quantities, a review of studies  into the toxicity of polyphenols has  shown.
"People shouldn't be too alarmed  by  this, but those taking supplements may experience problems," says  lead  author Chung Yang of Rutgers, the State University of New Jersey.
He  stresses that up to 10 small cups  of green tea a day is fine. Problems  are likely in people who take  supplements, which can contain up to 50  times as much polyphenol as a  single cup of tea.
Yang's  review cites experiments in  which rodents and dogs died from liver  poisoning when given very large  doses of polyphenols. He also reports  cases of people with liver  toxicity after overdosing on green-tea-based  supplements. Their symptoms  disappeared when they stopped taking the  pills, only to return when  they started taking them again
  



