That's very interesting... Here's one rule of thumb that I think everyone should consider:
Just because some is good doesn't mean more is better.
It's always a good idea to check out anything you're ingesting, be it a new vitamin, an herbal remedy, an over-the-counter remedy, a prescription medicine, or in this case, even tea! Just about anything has an upside and a downside--and overdoing anything is a really bad idea.
(Tylenol is a case in point--it is actually toxic to the liver if you take more than the recommended dose. It has been known to cause death in cases of overuse.)
"My religion is kindness." --His Holiness the Dalai Lama