The basic components of chewing gum are gum base, softeners, sweeteners and flavorings. Gum base is what makes the gum chewy. When gum was first discovered it was made from tree saps called “chicle” from the sapodilla tree. However, today gum base is usually made out of a mix of rubber and artificial materials. Then gum makers will add a softner to the gum base to prevent it from hardening. Lastly, they will add sweetners and flavorings to the gum base.
When you chew gum, the saliva in your mouth begins to digest the sweeteners and flavorings in the gum. Unlike the gum base, the other ingredients can be broken down and digested. As you swallow while you chew, the digested sweeteners and flavorings move through your digestive system to your stomach. Eventually, you digest all the sweeteners and flavorings, and all you’re left with is the gum base and softeners. That’s when you sense that your gum has lost its flavor. {1}
{1} http://www.ehow.com/info_8196200_causes-gum-lose-its-flavor.html