What is the role of vegetarianism in the yogic philosophy?

Before I started the Yoga Teacher Training Course I assumed that practitioners of yoga were “supposed” to be vegetarian but I didn’t know why.  I came to this conclusion because I met people who practiced yoga and vegetarianism, and I also visited ashrams where a vegetarian diet was followed.  From this I decided that vegetarianism must be to do with the notion of “karma” that I had heard about and vaguely understood.
But now that I am learning the philosophy of yoga, I am learning that there are many reasons that suggest a practitioner of yoga should be vegetarian.  Whilst these reasons fall under the realm of philosophy, medical and scientific evidence supports them.
On a practical level, being vegetarian can help one’s yoga because it is likely that food will be digested easily.  Of course this is assuming that one is following a healthy vegetarian diet, high in what is referred to as sattvic foods in the yogic philosophy  – a diet of fruits and vegetables and unprocessed whole grains.    Indeed any diet that is high in processed foods, frozen ready meals, and deep fried foods is going to conflict with good yoga practice whether you are following a vegetarian or omnivorous diet.
Beside the belief that sattvic foods should make up the whole or the majority of ones diet, this yogic philosophy of sattvic food alone does not advocate vegetarianism.   Further evidence to support vegetarianism can be found in the Eight Limbs, or eight key principles, that were scribed by the ancient sage Patanjali.
One of the limbs, or principles, concerns Yamas.  Yamas are behaviours that should be dissolved in order to achieve good karma and overall well-being.  One of the Yamas is ahisma, which is translated as non-violence and non-injury to others.  It is clear that following a vegetarian diet is a positive step to committing to dissolving the ahisma in one’s life.
From a scientific perspective, the ideal pH of the human body is 7.4 which is slightly alkaline.  When the body is maintained at this pH level, there will be improved immune function, reduced pain and inflammation, slower aging, and healthier teeth and gums which can help to prevent heart disease.  The simplest way to keep the body’s pH at 7.4 is to eat a diet that is high in fruit and vegetables – a hunter gatherer’s diet as some people refer to it.  In fact, the hunter gatherer diet is what many believe our bodies are originally intended to survive on: human’s lack the powerful jaw and sharp incisors to eat meat, and our intestines are similar in length to other vegetarian animals and not to carnivorous animals.   It has been suggested that humans began relying on meat when their vegetarian sources of food were scarce, and that it has become more of a cultural habit than a physical necessity.
Just as asana can bring about a new level of consciousness of our bodies, our alignment and our physical presence, so too can practicing vegetarianism bring consciousness to what we are eating.  In the yogic philosophy eating is not about enjoyment and, in the extreme, succumbing to cravings and feasting and gluttony.   It is about nourishment and eating enough to support our physical work, and no more.   In today’s world we are all aware of the dangers that obesity can cause, and the damaging effects that it can have on our health. Perhaps the consciousness and awareness that can come from adopting a well-rounded vegetarian diet would address this.
Ultimately, as food is a vital nutrient and our bodies our unique, we must each find the diet that works best for our own selves.  In writing this article I wanted not to advocate or even suggest a particular diet, but to provide a deeper understanding and insight into the yogic philosophy and why practitioners of yoga may choose to follow vegetarianism.