Bread was a staple for the Nolan family in Betty Smith's A Tree Grows in Brooklyn. The family made the most of the the bread in the household. Not only did the family treasure fresh bread, Katie Nolan learned ways to make stale bread delicious. 

The Nolans practically lived on that stale bread and what amazing things Katie could make from it!

Katie would make savory and sweet meals and desserts from stale bread. The creativity which Katie used to transform the stale bread into delicious creations could surprise even the best chefs. 

The bread, symbolically, represents the ability to make the most out of life and what one is given. One can choose to lay down and give up when presented with "bread crumbs." Others, like Katie, choose to make the most out of what they are handed. They will take the crumbs, transform them into something brilliant and new, and make the most out of life. The bread symbolizes both the life force of the family (their staple) and their creative forces (used to make the most of life).