Our Neshama (soul) which is the spiritual part of life, depends on food which is physical. How come? It should depend on something spiritual not physical. Kabala explains that all food that we eat has a spiritual part in it that goes to the Neshama. Kosher food has positive spirit and non-kosher food has negative spirit.
Eating kosher allows us to understand the reasons for mitzvot. Once a woman asked a rabbi the reason for certain mitzvahs. He asked her to eat Kosher for a month and she would understand.