The Belief of Ahimsa
Literally the avoidance of harm and violence, which applies to all living things, not just sentient life. It is an important article of faith when thinking about Hindu or Jian diets which are all taken from this core belief. The belief being that all living beings are a connected unity and therefore should each organism should be respected as much as the other. In some cases this will lead to a Fruitarian diet, which will only allow for food that has parted from the plant naturally, berries, seeds and beans which fall from the trees or meat that has died naturally.
You will find that many Hindu sects still adhere to this belief with strict vegetarian undertones, modern movements of the faith will not only avoid any animal but will also abstain from certain strong vegetables like onion and garlic. These are believed to have negative properties, they also fall under root vegetables and to pull a plant from the ground is to cause it harm.
Hindu movements such as Swaminarayan and the International Society for Krishna Consciousness will follow this, while of course being devoid of meat, eggs and seafood.
The concept is seen as pure diet, that it should mirror the qualities of nature itself and aims to promote a purity within the individual.
In Jainism, they will also abide to these laws although it will be done much more vigorously, being more easily compared to that of a Vegan or Fruitarian, the very nature of consuming animal products is seen as unacceptable in the diet. Scholars of the faith are much more likely to be active supporter of Veganism. They will go out of their way to avoid harm to animals, insects and even plants to a large extent, minimising any damage to life unless absolutely necessary for human survival, going as far as to not leave the home during the night because of the increased risk of accidental harm to insects and plant life.
Both diet's however tend to follow the basic pattern of Vegetarianism, altering between the allowance of dairy products and strict Veganism. The primary source of energy comes from a selection of berries, nuts and beans. With fruits and Vegetables to cover most other nutrients, those taking a lax approach to the diet may also include root vegetables such as potatoes.