Tea is rich in polyphenols like the catechin epigallocatechin gallate (EGCG). This catechin accounts for about a third of the weight of dry green tea and is the most important antioxidant in tea.
The highest concentration of EGCG contains white, followed by green tea. In black tea, the concentration of EGCG is lower since they are converted into theaflavins by oxidation In addition to EGCG in tea are found various other catechins. The most important are epicatechin (EC), epicatechin gallate (ECG) and epigallocatechin (EGC).
Besides the health benefits of catechins they have the disadvantage to make the tea bitter and tart. The addition of milk to tea makes it more mellow but since milk binds the catechins also a part of the health effect will be lost.