“We are what we eat”. The nutrients and energy within our body is composed of the food that we intake. Moreover, our thoughts and physiology are also determined by the same. This is because all the nutrients that are essential for the growth of the body are extracted from the food we eat. Thus, in Ayurveda, Aahara is of great importance.

The basics of Ayurveda rests in maintenance of equilibrium of Doshas, Dhatus and Mala.
All these three are nourished by the influence of Agni and the nutrients produced are passed to each level of Dhatu for nourishment. Thus, the nutrients that are essential for formation and development of tissues are supplied by one stream of pool. In Ayurveda, Aahara is of great importance amongst the three Upastambhas i.e. Aahara, Nidra, and Bramhacharya. The nutrition within the tissues is brought in by various mechanisms like Kshira Dadhi Nyaya, Kedari Kulya Nyaya, Khale Kapota Nyaya and Eka-Kala Dhatu Poshana Nyaya.

According to modern science, the nutrients are transferred to each tissue by two mechanisms: Active transport and Passive transport. Passive transport is the transport of nutrients or substances along the concentration gradient or electrochemical gradient or both. It is also called diffusion or downhill movement. It includes simple diffusion and induced diffusion. Osmosis can be regarded as a special type of Passive transport.

On the other hand, Active transport is transport of nutrients or substances against the electrochemical gradient. It is also called an uphill movement. Active transport requires energy for the transport.

In ayurvedic context, this transport of nutrients is brought in by various mechanisms as noted below:

1.Kshira Dadhi Nyaya

2.Kedari Kulya Nyaya

3.Khale Kapota Nyaya

4.Eka-Kala Dhatu Poshana Nyaya

1.Kshira Dadhi Nyaya:
Kshira – Milk
Dadhi – Curd

According to this theory, as milk is completely converted into curd, similarly, the first Dhatu formed from the digestive essence of food, by the action of Dhatu Agni it gets converted into succeeding Dhatu, completely. It means that, Rasa Dhatu which is formed from the essence part of the digested food, is completely converted into Rakta Dhatu. Further, Rakta Dhatu is converted into Mamsa Dhatu, and so on. This complete conversion of one Dhatu to another one is termed as Sarvatma Parinama or Total Bio-conversion.

The Rasa Dhatu is converted into Rakta Dhatu, Rakta Dhatu is converted into Mamsa Dhatu, and so on upto Shukra Dhatu. This process is governed by Dhatu Agni and total conversion is done on the 7th or 30th day.

The sequential conversion of substances is supported by this Nyaya. The various biochemical
transformations like glycolysis pathway, Kreb’s cycle, Gluconeogenesis pathway, urea cycle,
etc. are supported by this Nyaya.

2.Kedari Kulya Nyaya : Theory of transmission
Kedari – Paddy field
Kulya – Canal

According to this theory, the process of nourishment of the tissues can be compared to irrigation in the field by water from a canal. The water from the canal irrigates the part which is nearest to it and then the other parts through which it passes. As Rasa Dhatu is nearest, the essence part of the food reaches to it via the channels for nourishment. After the nourishment of Rasa Dhatu, the essence part is transferred and nourishment of Rakta Dhatu is accomplished. In this way, the essence part of the food is transferred to all the tissues leading to their nourishment.

According to this theory it is clear that Dhatus obtain their nutrients from the essential part of food and are transported via a channel within the body. Also, Dhatus get nourished by a specific part of Ahara Rasa (essence part of food).

This Nyaya explains the importance of pressure gradient, which indeed determines the process of flow of fluid within the tissues. It also explains the passive diffusion of nutrients across the cell membrane along with concentration gradient. Diffusion, Induced diffusion, filtration and osmosis are supported by this Nyaya.

3. Khale Kapot Nyaya : Theory of selection
Khale – Threshing floor
Kapota – Pigeon

The way a pigeon pecks the grain from a threshing floor and carry back to their nests; similar, when the essence part of food is transported to the Dhatus, every Dhatu selects the required essential part of the food, which contains the nutrients required for their nourishment. The nutrients are transported via a channel known as Srotas. Thus, it is clear that replenishment of tissue is a uniform sequential process.

Any process that requires energy to maintain homeostasis within the body like primary active transport, secondary active transport, selective reabsorption, etc. are supported by this Nyaya.

4.Eka Kala Dhatu Poshana Nyaya : Theory of simultaneous process

Ayurvedic scholars have mentioned that Aahara is an essential part of living and Aahara Rasa is circulated all over the body continuously by normal activity of Vyana vayu. As Aahara Rasa percolates into all the Dhatus via Srotas, this theory is known as Eka Dhatu Poshana Paksha.

According to this theory, formation of Dhatu from Aahara Rasa is a cyclic and continuous process. This theory also states that all the Dhatus are nourished at the same time via different processes of Kshira Dadhi Nyaya, Khale Kapota Nyaya and Kedari Kulya Nyaya.

Thus it can be concluded that the concept of Nyaya is equivalent to various physiological processes during the metabolic processes.