There are no added preservatives in cassava bread. Instead, it is preserved by drying in the sun. If you are looking for a naturally preserved food, cassava bread should be your choice. Young tender cassava (yuca) leaves are a good source of dietary proteins and vitamin K. Vitamin K has a potential role in bone mass building by promoting osteotrophic activity in the bones. It also has established role in the treatment of Alzheimer s disease patients by limiting neuronal damage in the brain.