Why Do frogs eat their shed skin?

The frogs appear to be climbing out of baggy wet clothing as they scramble to get their old skin off. They also eat it as it comes off which scared me the first time I saw it because I thought he was caught in debree or eating something that should not be in the tank. As I looked closer I realized that it was his old skin. Looking at his tank buddy he was also doing the same thing. After doing a little research I found out that this is normal and the skin is good for them. They appear to choke on it a little as it goes down, a little like watching a snake eat. Then they are look all bright and fresh :) Hope that helps, I am still a bit of a novice my self. Sounds like they shed every few weeks and it is not a sign of distress or anything.