To be able to maintain a balance in the body, one needs to first understand the composition of the body. According to one definition given in ayurved, the body is composed of Doshas, Dhatus (tissue elements) and Mala (excreta) ("Dosha Dhatu and Mala mool hi shariram,") i.e. to say that the combination of Doshas Dhatu and Malas make the human body. A body, which is in state of balance, represents the factors derived from five Mahabhutas (elements) and is the site of manifestation of consciousness.
Dhatus are the tissue elements in the body that when become discordant cause disease or destruction of the body. Any increase and decrease in the amount of dhatus results in a disease. Dhatus are eight in number: Rasa (lymph), Rakta (Blood), Mansa (Muscle), Meda (Fat), Asthi (Bone), Majja (Marrow), Sukra (Semen), and Ojas.
Just like Doshas, dhatus having opposite qualities undergo increase and decrease simultaneously. Increase in dhatu of one quality causes decrease in dhatu of opposite quality. That's how ayurvedic therapies when properly given simultaneously bring both reduced and increased dhatus to a state of normalcy by reducing the increased ones and increasing the reduced ones.
For maintenance of equilibrium of dhatus one is advised to keep the following in consideration.
Diet and regimen should be in accordance with the location, season and individual constitution (Prakriti) of the individual.
One should refrain from excessive, wrong and non-utilisation time, intellect and objects of senses.
One should not suppress manifested urges.
One should refrain from excessive physical labour beyond one's capacity.
The nature of food eaten affects the dhatus in the body food having opposite qualities to that of dhatus reduces those dhatus in the body and similar qualities increase. Ayurved says "samane samano vriddhi..". For example fat (meda dhatu) gets increased by adding fat in the diet. Mansa (muscle) gets increased by intake of meat, bone by cartilage, Majja (bone marrow) by bone marrow.
When a particular dhatu is to be increased and the same kind of food cannot be taken because of any seasons like non-availability, dislike etc then food of a different nature, but having predominance of the attributes of the dhatu should be given. For example, diet for semen-milk, ghee, honey etc are cold sweet, unctuous. Dimunition of urine-sugarcane juice. Dimunition of vata-pungent, bitter, astringent.
Dhatus get nourished by the food that we eat. Food eaten is broken and transformed into two parts-prasad which gets utilised by the body and mala i.e the waste, which is ejected from the body. Vata in the body transports the food eaten.