The juices in our core cleanses have zero added processed sugars, what they do have is fructose, which is naturally occurring in fruits and vegetables. Fructose is an important source of energy for the body, our body functions, and especially the brain. On a juice cleanse we need a source of energy, otherwise our bodies would shut-down. If the body can’t find ample amounts of energy it will undergo protein catabolism, where it will find a way to produce the glucose by synthesizing protein (via amino-acid degradation) through the liver. This process results in destruction of muscle mass and a general substrate overload in the liver, which is the complete opposite of what we are trying to achieve in a cleanse.