There is a relationship between diet and spirituality. There is simply no separation between the physical and the spiritual.
Most spiritual traditions advocate a simple life and a life of moderation.
In addition, love and compassion are key virtues promoted not only towards humans but animals and nature. The Buddha taught compassion towards all beings and animals. Unlike the passover of old, Jesus Christ initiated a vegetarian passover (The Eucharist) of bread and wine, symbolizing a non violence communion.
In modern terminology, we called it an eco friendly diet. We cannot deny that a plant based diet is more in line with an eco friendly diet.
Not of all us may be suitable or ready for a 100% vegetarian diet. Yet to be healthy in body, mind and soul, we should strive towards a plant based diet. It is good for health and good for mother earth.