"To become vegetarian is to step into the stream which leads to Nirvana" - Buddha
I suspect it is a common feeling especially since many religious beliefs throughout history have recommended shunning meat diets as a way to reach a higher level of purity and consciousness. In fact, if one feels that all life was created from a divine being, then bringing harm to any of those creatures for any reason could be perceived as a disrespectful action. Such is one foundation of the connection between diet and spiritualism. Beyond the arguments of logic, many on their spiritual path feel, emotionally or physically, that it is just the best thing to do.
One discussion in the book which was intriguing is the concept that food has a life force that "can be felt as energy that we plug into for our physical, emotional, and spiritual renewal."
When an apple is growing on a tree, drinking in the sunlight, it is filled with the energy of life. That energy is what we call the "life force". Once the apple is picked , it still contains much of ifs life force. The life force keeps the apple firm, juicy, and sweet. However, several variables can affect its life force.
Source: Eating in the Light (c) 2001, Hay House Inc.
If we consume high life force foods we should reap the reward of higher energy levels and vitality which results in positive forces and progressions in our personal and spiritual lives and a prolonged duration of the life force that makes us who we are!