How does tea affect blood pressure levels?

There is good amount of hype in connection to tea these days. It is believed that green tea is beneficial for heart and therefore the blood pressure levels too. Green tea is believed to be rich in antioxidants and due to this it reduces the bad cholesterol in the body and avoids hardening of the arteries. Green tea also discards blood clotting possibility from the system and has anti-inflammatory effects on the body. But some health experts believe that green tea must be consumed moderately. This is because too much can also be harmful and may increase blood pressure. Even white tea is beneficial if consumed moderately for preventing blood pressure.
As far as research on black tea is concerned, here are the details: