When we perform any physiological actions, we need certain energy. During this process, the tissues are constantly formed and destroyed. They acquire nourishment via the air, water, and food.

The food that we consume every day is not soluble into our body. It is made soluble by action of many entities present within. Those entities start to break down food into its components, extract nutrients from it, transport it to every tissue in the body and lastly, the waste generated in the entire process is thrown out of the body.

But what are those entities which bring about all these activities?

Ayurveda describes this entity as Agni. Ingested food is digested, assimilated, and absorbed by Agni. Agni converts food into a form of energy, which is used to perform vital functions of our body. In Ayurveda, Agni is considered as the cause of life, complexion, strength, health, nourishment, and luster. Acharya Charaka says that, when Agni stops, the individual dies; and when the Agni is present, a person is alive. In proper balance of Agni, all the metabolic processes work in peace, but when Agni is vitiated, the whole system is disturbed resulting in ill health. Thus, Agni is considered as the Moola (base) of life.

According to modern science, metabolic processes are carried out in cells and cells are divided and multiplied from birth till death. These cells are termed as Paramanu in Ayurveda. When a group of Paramanu combine, they give rise to various Dhatus (tissues). Each cell and tissue contain Agni to provide energy throughout the body.

Agni is innumerable as it is present in every Paramanu (cell) and Dhatu (tissue) within the body. Based on the functionalities of Agni, it is divided into 13 types:

1. Jatharagni – Agni which is present in the stomach and duodenum.

2. Bhutagni – These are five in number – of five basic elements (Panchamahabhutas).

3. Dhatwagni – These are seven in number – of seven Dhatus within the body.

Jatharagni:

Jatharagni is the Agni present in Jathara (stomach and duodenum). It is responsible for Ojas, duration of life, health, strength of Dhatus, Dhatu Agni and Bhutagni. Jatharagni digests the food which contains the Panchamahabhutas and transforms it into the form in which Dhatus can utilise its nutrients. It is also responsible for segregation of Prasad (essence) and Kitta (waste) portions in the body. It is related to Dhatu Agni with the tissue metabolism process. Thus, Dhatu Agni depends on Jatharagni. Further, Jatharagni is classified into four types depending on the actions for digestion in the human body.

1. Vishamagni – This type of Agni overlooks the speed of digestion i.e., fast, and slow. When this Agni is affected by Vata Dosha, it may lead to various udara gata roga.

2. Tikshna Agni – It is responsible for the very quick process of digestion of food, regardless of food type. Very quick process of digestion may lead to hunger, and when the food is digested, it dries off the throat.

This condition is known as Bhasmaka Roga.

3. Mandagni – It is responsible for a very slow digestion process. In this, Agni digests the least amount of food in the greatest amount of time.

4. Samagni – This is responsible for digestion and assimilation of food properly at proper time. It increases the quality of Dhatus.

Bhutagni:

This Agni is present in Panchamahabhutas which are Prithvi, Jala, Tejas, Vayu and Akash. Every cell of the human body is composed of these Panchamahabhutas. Aacharya Charak says that the five Bhuagnis digest their own part of the element present in the ingested food. Bhutagni acts after Jatharagni i.e., after the disintegration of food. Bhutagni can be referred to the juices present in the liver, which are responsible for conversion of digested materials.

1. Prithvi-agni : It is related to earthy elements of the food and nourishes the nose sensory organ.

2. Ap-Agni : It is related to the water element of the food and nourishes taste buds in the tongue.

3. Tejas-Agni : It is related to heat and energy of the food and nourishes the sense organ of the eye.

4. Vayu-Agni : It is related to the air element and nourishes the sense organ of touch or skin.

5. Akasha-Agni : It is related to space elements and nourishes the sense organ of hearing in ears.

Dhatwagni:

All the seven Dhatus of the human body have their own Agni to metabolize nutrients supplied to them.

1. Rasagni is present in Rasa Dhatu

2. Raktagni is present in Rakta Dhatu

3. Mamsagni is present in Mamsa Dhatu

4. Medhagni is present in Medha Dhatu

5. Satyagni is present in Asthi Dhatu

6. Majjagni is present in Majja Dhatu

7. Shukragni is present in Shukra Dhatu.

Each Dhatu Agni synthesizes and transforms constituents suitable for a particular Dhatu. These are selective in nature. Each Dhatu Agni transforms and digests the nutrients they require and enhances the nourishment of Dhatus.

Thus, all the different types of Agni bring in about the digestion and metabolism of the ingested food. In medical science, the term Agni can be regarded as metabolites which do the same task as that of the Agni. Modern medicine or Ayurveda, our body is based on certain principles, which are thoroughly explained. Agni referring to just one word “fire” represents the entire digestive process.