Kosher is discussed at length in Jewish law and in mystical philosophy.
Kosher food is “health food” for the soul.
According to the Kabbalah, eating is a process of purification. When we eat, we separate the coarse material from the Divine energy in the food. Everything in the world contains some sort of Divine energy. But non-kosher foods are too “coarse” for us to purify by eating. Rather than providing spiritual energy, once metabolized, these foods actually stand in the way and block energy flow.
On a deeper, more mystical level, keeping kosher keeps a human soul sensitive to spiritual matters. This is clearly a mystical concept and not immediately perceptible to our physical senses. Nevertheless, it has been asserted by numerous Jewish sages throughout the ages. Just as excessive consumption of certain foods may be physically unhealthy, non-kosher foods are spiritually unhealthy. Just as there are foods that are friendly to your body and foods that harm it, so too there are foods that are soul-friendly while other foods are not-so-friendly. They clog our “spiritual arteries” and prevent those warm, healthy spiritual feelings from circulating through our psyche and consciousness.