The biological fire that governs metabolism, agni, encompasses all the changes in the body and mind from the dense to the more subtle. Such changes include the digestion and absorption of food, cellular transformations, assimilation of sensory perceptions and mental and emotional experiences. Agni covers all the sequences of chemical interactions and changes in the body and mind. Digestive abilities are directly proportional to the strength of agni. Agni and pitta are closely connected. While both are hot and light, agni is subtle and dry, while pitta is gross & liquid. The heat energy to help digestion contained by pitta is agni. Pitta is the container and agni the content. Agni is acidic in nature and stimulates digestion. It is subtly related to the movement of vata. In every tissue and cell agni is present and is necessary for maintaining the nutrition and auto-immune mechanism which is performed by destroying micro-organisms, foreign bacteria and toxins in the stomach and the intestines.
A balanced agni is vital for health. The strength of the body to resist disease and also its physical strength are directly related to its heat energy determining the metabolic processes of the body. Disturbances to Agni are usually the chief causes of disease leading to aama in the body. There are thirteen types of Agni (12 dhatva (tissue) agnis, & 1 jatharagni) in the body and mind according to the conversion and the transformation made. The most important of them is the Jatharagni, the gastric fire. It is responsible for digesting the food eaten (it can be loosely correlated to hydrochloric acid in the stomach and the digestive enzymes and juices secreted into the stomach, duodenum and the small intestines). If digestive agni is low and its capacity is impaired, one may experience pain, discomfort, feeling of heaviness or gases gurgling, constipation or loose stools based upon the prevalence of disturbance and imbalance.
*In such conditions one should practice the sansarjana krama, preventing the accumulation & production of ama & thus diseases.