The Digestive Process, in brief:
Jatharagni (a collection of bio-chemicals, enzymes etc.), holds the food for certain time (called Pittadhara) inside the stomach (Amasaya) for proper digestion to take place. The duodenum is situated at the entrance of the small intestine (from stomach to small intestine). Its good functioning is essential for a healthy human body.
If it is weak, it allows uncooked food to pass on to the intestines, and as such, Rasas and other Dhatus do not get properly formed.
Aharapaka (Digestive Process):
The food taken at the proper time (not at night 1100 PM!), is drawn into the Alimentary canal by the Prana Vayu; The hard/big mass of food is split into minute pieces/made soft by the liquid; The Jatharagni, then, activated by the Samana Vayu (Present in the Naval Region) digests the food.
Though the food may consists of any/all tastes, it first becomes Sweet (Madhura), which produces Kapha; Further cooking/digestive action makes the food Amla (Sour), thus producing Pitta; and, thence getting expelled from the stomach, to Duodenum, it gets dried, becomes solid and Pungent (Katu), finally producing Vata.
The Salivary secretions and Alkaline fluids of stomach, renders the food to become Fluid and Homogenous, on which The Digestive Fire may then act. Most Kapha problems (Nausea, Lack of Appetite, Vomiting Phlegm etc.), occur at this stage. This results from indiscriminately eating Kapha Increasing Diet (Heavy, Over-cooked, Sweet, Salty stuff).
These stages together (Avasthapaka), form the First Phase of the Digestion.
Further Phase of Digestion:
The Bhutagnis (The 5 Bhutagnis), reside in the Liver, and turn the food that we take, to the 5 respective elements (The Panch Bhuta), which then form the respective tissues of our body. Each Bhutagni acts on its own kind of food, such as Parthivagni on Prithvi, Apyagni on Apya, and so on for Agneya, Vayavya and Nibhasa. This is the second stage, Nisthapaka.
‘Pitta’ secretions from Liver, Small Intestines and Pancreas are involved here. Pitta problems, like Hyperacidity, Ulcers etc. occur at this stage. Usually caused by Over Drinking of Liquor, Hot & Pungent Foods.
After the end of the two stages of digestion, the digested food gets divided into the waste (Kitta) and the essence (Sara). Liquid portion of waste material forms Urine and the solid material faeces.
The Final Phase of Digestion occurs in the Colon, where absorption of the elements take place, and waste materials are expelled.
The essence undergoes further transformation by the bio-chemical reactions by the Seven Agnis (Dhatvagni) present in each of the Dhatu.
The digestive Fire (Jatharagni) Types:
Jatharagni is normal, when Samana Vayu is at its normal seat (i.e. Stomach) (Samagni); It gets deranged/erratic when it is in the wrong path (Vishamagni); It gets very strong (Tikshna), when Samana Vayu is associated with Pitta (Tiqshagni); and is weak (Manda) when the Samana Vayu is associated with Kapha (Mandagni). Now, there are total 13 types of Jatharagnis (The Jatharagni, 5 Bhutagnis, and 7 Dhatu Agnis), to digest anything that you may eat, obviously excluding, antagonistic foods, which are big deterrent for our body.
Such substances as Pure Desi Cow Ghee and Fresh Aloe Vera Juice/Gel help regulate The Elemental Digestive Fires.
Along with The Digestive Process, I must mention here, that The Subtle Component of V, P & K are The Prana, The Tejas, and The Ojas. It is This Tejas, The Subtle Agni, residing within us, which helps us realise the Divine Consciousness.