Termites eat the cellulose that is found within wood and plant cell walls. Although termites do not eat and gather nutrients from foam, drywall, lead and plastics, they often chew through the material.
The termites are able to digest the cellulose in wood and plant fibers in a way that no other animal can. Termites have bacteria that live within their stomach, and the bacteria helps termites digest these materials to obtain the nutrients from the cellulose, which is why termites can cause so much destruction within a home. The termite does not have any competition from other animals when it comes to eating wood, so there is no predator to stop them.