The Vedas teach Hindus to avoid some food items. The list includes not only non-vegetarian food but also old food items in the vegetarian categories too (older in this sense means food items which are put in the fridge for more than one day and also items like pickle.) Also, it is advised to avoid items with too much peppery, salty, and sour taste. What is the basis for this? Are there any specific reasons behind this categorization?
In vegetables there is but one active tattwa, or elementary condition of matter. That is jal, which means ‘water’. It refers to the liquid state of any substance. In insects there are two active tattwas, agni or ‘fire’, and vayu or ‘air’. Agni refers to the resolving state, or heat; it means a transitional state of matter. Vayu refers to the gaseous condition of matter. In birds there are three active tattwas: jal, agni and vayu. In the higher animals there are four active tattwas: prithvi (earth), jal, agni and vayu. But in man, and in man alone, all five tattwas are active. As a matter of fact, all five tattwas are in everything in the world, but they are not active. Akash is the last one, which is active in man alone.
Now, the law by which we are governed is this: The greater the number of active tattwas that are combined in the living individual, the higher he is in the scale of evolution and also the greater the responsibility involved in killing that individual – hence, the greater the burden of karma assumed in killing. But since man has to eat something in order to continue his life here, the ancient sages and Masters selected the least harmful substances, that is, those things in the killing and eating of which there is the least karma to be assumed. They decided on vegetables; no animals at all. Of course, there is some karma to be assumed in eating vegetables, as there is life in them too. But in vegetables there is the lowest form of life, and hence the least karma involved. This is the chief reason why the saints do not approve of killing and eating animals. The second reason is that the eating of animal food interferes with one’s spiritual refinement. It drags a person down toward the animal plane. It is a fact that as long as one eats animals, he will be more or less like animals. It is unavoidable that we should become like what we eat, just as we become like that of which we constantly think. We must absorb its qualities to some extent. How could it be otherwise? That is but common sense, and I believe most people will agree to it. It may be tested by anyone. A heavy animal diet will always awaken the animal passions and drag one’s thoughts down to the animal plane. But the disciples of the saints have as their chief aim and effort in life to rise above the animal plane and to unfold their spiritual powers. Hence they must not eat that which will pull them down to the animal level.
Vegetarian and vegan ethics are not a recent fad in Asia, but a longstanding human aspiration and virtue- Mercy towards animals
The answer to this question is given in the Gita shlokas 17.8-10.
Persons who are Sattvika by nature like foods that promote longevity, vitality, energy, health, happiness and cheerfulness, as also those that are juicy, soft, nourishing and agreeable. Gita 17.8
Persons who are Rajasa by nature like foods that are bitter, sour, salty, excessively heating, pungent, burning and thirst-producing as also what bring on uneasiness, depression and disease. Gita 17.9
Persons who are Tamasa by nature like foods that are stale, tasteless, putrid, decayed and unclean, and constitute the leavings of others. Gita 17.10
Gita seems to suggest that salty, sour types of foods encourage rajasa and can bring about depression and disease.