[jurjenh]

Just googling it (because I've heard it from several places) that the longer rising of bread does start to break down some of the gluten (hence making it easier to digest)

Fermentation of proteins. Some bacteria of the genus Clostridium (putrescent anaerobes) are able to ferment amino acids as well as carbohydrates. These bacteria are better adapted to utilize proteins, which they break down to amino acids by means of proteolytic enzymes; the amino acids are then fermented. The process of protein fermentation is important in the circulation of matter in nature.

source: http://encyclopedia2.thefreedictionary.com/Fermentation+Proc...