What are the Different Types of Food?
There are different kinds of food. Firstly, tamasic food that is food which is stale or rotten with the virtue gone out of it. Secondly, rajasic food that is the food which is too acrid, pungent etc., heats the blood and spoils the health. Thirdly, sattwic food that is the food which is pleasing, healthy etc. Different kinds of food nourish the action of the different gunas and so indirectly are helpful or harmful apart from their physical action. 
What is the Ideal Food?
Clearly out of rajasic, tamasic and sattwic foods, from the perspective of inner and outer hygiene, sattwic food is preferable. However, what particular eatables are or are not sattwic is another question and more difficult to determine. Spiritually, I should say that the effect of food depends more on the occult atmosphere and influences that come with it than on anything in the food itself.  When we eat, we should be conscious that we are giving our food to that Presence in us. 
Rajasic-tamasic food is excitant of certain strong material-vital forces. It is obvious that if one wants to conquer the physical passions and is still very much subject to the body nature and the things that affect it, free indulgence in rajasic-tamasic is not advisable. 
It is only for those who have risen above the body consciousness and mastered it and are not affected by these things that it does not at all matter; for them the use of this or that food or its disuse makes no difference. At the same time the abstinence from rajasic or tamasic foods does not of itself assure freedom from the things they help to stimulate. 
About food, the aim of Yoga is to have no hankerings, no slavery either to the stomach or the palate. 
Vegetarianism is another question altogether; it stands on a will not to do harm to the more conscious forms of life for the satisfaction of the belly. 
There so many contradictory reports on the effects of food, spices, etc., that food must be—like all the rest—a personal affair and consequently no general rule can be made and, still less, enforced. 
Why is Food Important?
Food is taken as a means for the maintenance of the physical instrument only. 
… people who work in order to develop their taste, to refine it, are rarely very much attached to food. It is not through attachment to food that they do it. It is for the cultivation of their senses, which is a very different thing. 
How to Eat Consciously ?
With food, we daily and constantly take in a formidable amount of inconscience, of tamas, heaviness, stupidity. One can't do otherwise—unless constantly, without a break, we remain completely aware and, as soon as an element is introduced into our body, we immediately work upon it to extract from it only the light and reject all that may darken our consciousness. 
Food as a Small Concern
To be always thinking about food and troubling the mind is quite the wrong way of getting rid of the food-desire. Put the food element in the right place in the life, in a small corner, and don't concentrate on it but on other things. 
Food as an Offering
When eating one aspires that this food may not be taken for the little human ego but as an offering to the divine consciousness within oneself. In all yogas, all religions, this is encouraged. This is the origin of that practice, of contacting the consciousness behind, precisely to diminish as much as possible the absorption of an inconscience which increases daily, constantly, without one's being aware of it. 
Detachment and Equanimity
It is not by abstaining from food that you can make a spiritual progress. It is by being free, not only from all attachment and all desire and preoccupation with food, but even from all need for it; by being in the state in which all these things are so foreign to your consciousness that they have no place there. 
It is an inner attitude of freedom from attachment and from greed for food and desire of the palate that is needed, not undue diminution of the quantity taken or any self-starvation. One must take sufficient food for the maintenance of the body and its strength and health, but without attachment or desire. 
One must be calm and equal, not getting upset or dissatisfied when the food is not tasty or not in abundance—eating the fixed amount that is necessary, not less or more. There should be neither eagerness nor repugnance. 
Some helpful practices for having food in a conscious manner.
… before you eat, concentrate a few seconds in the aspiration that the food you are about to eat may bring your body the substance it needs to serve as a solid basis for your effort towards the great discovery, and give it the energy for persistence and perseverance in the effort.
Cite error: Closing
</ref> missing for
Children should be given food that suits their temperament, prepared in a way that ensures hygiene and cleanliness, that is pleasant to the taste and yet very simple. This food should be chosen and apportioned according to the age of the child and his regular activities. It should contain all the chemical and dynamic elements that are necessary for his development and the balanced growth of every part of his body. 
In conclusion, if one wants to see the truth of the problem, it is this: only an enlightened body, balanced and free from all vital desire and mental preconception, is capable of knowing what it needs in regard to quantity and kind of food. It is extremely exceptional to find such a body, thus, one must act for the best with non-attachment and equanimity and not attach too much importance to it.