EGCg is a polyphenol antioxidant found in tea leaves, most notably in green tea. Polyphenols, like EGCg, have free radical-scavenging abilities that protect cells and tissues from damage and prevent against the development of certain cancers.  EGCg is also known to strongly enhance the immune system. Due to this product’s antioxidant effects, this product should be avoided 1 week before, during, and for 4 weeks after radiation.
 
References:
A Comprehensive Review on the Effects of Green Tea and its Components on the Immune Function
 
Green Tea Compounds in Breast Cancer Prevention and Treatment
 
Protective Effect of Green Tea Consumption on Colorectal Cancer Varies by Lifestyle Factors