There are a few reasons why vegetarianism (non-meat eating) is being promoted strongly by Buddhism and Yoga practice.
It is supporting the idea of non-harming or non-killing and compassion towards all beings including animals and insects.
It is more healthy to eat lots of fruit, nuts, beans and vegetables than to eat meat especially nowadays the meat is not really as healthy as before because most of the animals that are being breed for food consumption are not healthy physically and mentally due to poor living environment under the mass productivity in factories and farms. These animals are being treated badly and being fed with unnatural food and being injected with hormones. Even though most of the fruit and vegetables that we get from the market are not really healthy either due to chemicals and pesticides that farmers are using nowadays for their farms to induce growth and to protect their crops from insects. But still meat eating is causing more harmful effects to our body and the mind than non-meat eating.
There are lots of unhealthy food (meat or non-meat) in the market nowadays contain substances which can cause illnesses and cancers, such like colourings, preservatives, conditioners, artificial flavourings, MSG, sugar and so much more other chemicals that is in the food and drinks. Even in all the daily personal cleaning products or housing cleaning products are full of harmful chemicals. As well as all the high-tech electrical products and conveniences are bringing so much pollutions and damages into the nature and the living environment.
No doubt that vegetarianism is more environmental friendly. By supporting non-meat eating can help to maintain the nature as healthy as possible because massive meat productions do contribute to the global warming through lots of lands had been used to produce corn to feed the animals instead of having plants and trees that work as a filter system for the air that we breath in.
Vegetarianism is also conducive for controlling the mind and to control the strong lustful passionate desires. Anyhow not only meat eating can stimulate the passionate desire, violence and anger in us, but even some non-meat products like alcohol, garlic, onion and chive also have the substances that can stimulate the passionate desire and anger in us. While drugs that are plants origin is having the substances that can affect the mind and the body, causing psychology and physical health problems in us such like addiction, dullness and depression. No doubt that the energy that comes from fresh fruit and vegetables have the calming effects in the body and the mind.
But most important in Buddhism and yoga practice for supporting and promoting vegetarianism is for people to develop compassion and non-harming towards all beings and to have control over the mind to achieve tranquility and sharpness in the mind to allow wisdom to arise within us.
In Buddhism and yoga practice, the main practice is to deal with the strong desire of cravings and aversions towards what we see, hear, smell, taste, feel and think. It is the sensual pleasure enjoyments of likes and dislikes that is over powering most of the people’s mind, that creates greed and attachment in us which contribute to the unhappiness, frustration, dissatisfaction, irritation, disappointment and painful suffering in us.
Because most of us are still being influenced and affected strongly by the food and drinks that we consume as well as other inputs that we are receiving through our eyes, ears, nose, tongue, skin and thinking faculty which influence the energy fields in our body and affect the state of our mind, either agitating, stimulating or depressing. As long as we are still being influenced by all these substances, we need to choose what type of inputs that we put into our system in order to achieve control of the mind.
At the end, it doesn’t matter if it is vegetarian or non-vegetarian food that we eat, it is the non-attachment towards the taste of the food that matters most. And no matter what type of food that we eat, we should eat with appreciation and should show gratitude that these food are providing energy for us to survive and to maintain this body and to have the life for us to be here to learn, to experience and to become enlightened.
When we are not being influenced by the energy fields in our body anymore, and we are free from duality and are fully mastering our mind; have eliminated the ego and ignorance, and we have gone beyond all the names and forms; and there is no more differences between birth and death; and we are one with the universal consciousness that is without any attributes or intentions, and then we will know that the true self in all living beings are not touched by names and forms, and are beyond birth and death, good and evil. Until then we can go beyond “vegetarian” and “non-vegetarian”.
If we eat with our taste of likes and dislikes and being influenced by our cravings and aversions towards all the objects that we get in contact with through the senses, then we are still bound by names and forms, there is still a huge difference between meat eating (non-vegetarian) and non-meat eating (vegetarian). And by eating meat we are directly or indirectly involved in harming and killing the animals and caused fears, hatred and pain onto these animals’ minds.
But for someone who is truly enlightened and had gone beyond all names and forms, the entire world is nothing but just a projection of his own mind, and then what is “live” and “death”? What is “cravings” and “aversions”? What is “meat” and “not meat”? What is “vegetarian” and “non-vegetarian”? What is “healthy” and “not healthy”? What is “good food” and “bad food”? What is “hunger” and “survival”? What is “pure” and “impure”? What is “energy” and “elements”? What is “limitations” and “conditions”? What is “past” and “future”? What is “actions” and “karma”? What is “existence” and “non-existence”?
But for many of us who are still not at that level of enlightenment yet; still have lots of impurities and ignorance of anger, hatred, jealousy, arrogance and greed; still being influenced by energy and elements; still being affected by all the inputs that we received through the senses, and still have strong cravings and aversions; still have lots of needs and wants; still have fears and worries; still have the differences of happiness and suffering, success and failure, birth and death; and still being bound by the duality in all the names and forms, then know that we are still bound by what we should do and should not do.
Vegetarianism is one of the steps of purification for the body and the mind. But if we still have the idea that “this is good, and I like it” and “that is bad, and I don’t like it”, know that we are still not even at the first step of the real practice of non-attachment and non-dualism of namelessness and formlessness, but no doubt that eating good and healthy food that is bringing harmony to the body and the mind will still be a good purification process for the body and mind to move towards non-attachment and namelessness and formlessness.
Most important is the practice of self-control and eradication of anger, hatred, jealousy, arrogance, lust and greed. And also non-harming in thoughts, actions and speech towards all beings. And if this physical body is dead, “who” will mind that the worms and germs will be eating the flesh of this body and feed whatever animals that are in hunger. At least there is still a contribution towards other living beings and allowing other living beings to have the opportunity of life to evolve spiritually and be free from the conditions of life existence.
Merely by eating vegetarian will not guarantee a person to become enlightened or being happy in life and will be free from suffering. Neither by eating meat will stop a person from attaining enlightenment, being unhappy and unkind, or cannot be free from suffering. It is all in the mind.