Polyphenols are very strong, very effective antioxidants.
Green Tea  has the highest concentration of polyphenols. 30% of dry tea's weight is made up of polyphenols.

Studies have found that the polyphenols found in tea are extremely effective in blocking cholesterol from oxidizing and fouling blood vessels. One polyphenol, epigallocatechin gallate, neutralises up to five times as much LDL cholesterol as vitamin C, another  powerful antioxidant.

 Men who drink 4 cups of  tea per day, lower their chance of dying from heart disease by almost 58%.
Another study showed that men who drank more than 5 cups of  tea per day lowered their chance of stroke by 69%