It refers to the nutrition of different dhatus in the body through digested food (pachit ahar rasa). Three different theories exist in ayurveda that explain the process of nutrition of dhatu from the digested food (ahar rasa), namely :-

» Kshir Dadhi Nyaya
» Kedar Kuliy Nyaya
» Khala Kapot Nyaya

Kshir Dadhi Nyaya
Kshir means milk and Dadhi means curd. Like milk changes to curd, ahara rasa changes in sequence of nutrition of Dhatus. At first Ahar rasa completely changes to Rasa Dhatu, following this is the changing of Rasa Dhatu to Rakta Dhatu and so on. This is one of the ways of nutrition of different Dhatus.

As sunrays take many years to reach earth and still maintain its continuity by the continuous release of rays. Like wise it seems by this law, one Dhatu will completely end if it totally changes to other one. But due to the continuous flow of ingested food it does not occur.

Khala Kapota Nyaya
The word khala means pot and kapota means pegion, the bird. As the bird (pigeon) has to come to the pot of grain for its nourishment, like wise the Nyay Dhatus are directly nourished by Ahar Rasa without considering the sequence of nutrition. At times when there is shortage this law nourishes Dhatu or Updhatu in the body. So we can say there are three way of nourishment of Sharir Dhatus in the body. Which occur according to the need of the body.

Kedar Kuliya Nyaya
The word Kedar means small pieces of land and Kuliya means drain. Crops in the field get irrigated by creating Kuliya (drain) and Kedar (small pieces of land). The Kedar (small pieces of land) get irrigated one by one through Kuliya (drains) in sequence. Like wise different Dhatus of the body get nutrition one by one in sequence through vessels. The 1st Rasa Dhatu gets nutrition from Ahar Rasa. Then Rakta Dhatu get nutrition from the rest part of Ahar Rasa and like wise till the end i.e. Shukra Dhatu. Ayurvedic law of nutrition of dhatu is transformed as follows:

During the transformation first Ahar Rasa reaches Rasa Vaha Shrotasa the Rasa Dhatu Agni processed the Ahar Rasa. During this process it is divided into three parts - Sthoola (Macroscopic), Sukshma (Microscopic & male excreatory). The Sthoola part gives nutrition to the self Dhatu i.e. Rasa.

Sukshma part Nourish its descendent Dhatu i.e. Rakta Updhatu. Stamya and Mala nourish its mala i.e. Kapha in this case. This way the process of Dhatu, Updhatu and Mala takes place.