Catechin effect

So What is exactly Catechin? How does it effect human body??
Catechin is polyphenol active element, and also called as tannin too. This type of polyphenol element is seemed to be available only in tea (black tea, Wulong tea also have catechin.)
Green tea has much amount of catechin (sharing 8 to 15% in itself).

Effect to:
1 protect cancers, anticancer
2 high blood & sugar diabetes
3 anti-aging
4 help to lose fat